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1

Grade Assignments for Models Used for Calibration of Gross-Count Gamma-Ray Logging Systems (December 1983)  

Energy.gov (U.S. Department of Energy (DOE))

Grade Assignments for Models Used for Calibration of Gross-Count Gamma-Ray Logging Systems (December 1983)

2

Gamma-Ray Logging Workshop (February 1981)  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

Borehole logging methods for exploration Borehole logging methods for exploration and evaluation o f uranium deposits . Philip H. O d d , Robert F. Bmullad and Carl P. Lathan rej~rinkttl fnlm Mining and Groundwater Geophysiall967 Borehole logging methods for exploration and evaluation of uranium deposits Philip H. Dodd, Robert F. Droullard and Carl P. Lathan US. Atomic Energy Commhwn GmrPd Jtinct&n, Colorado Abstract, M o l e 1 - i s thc geophysical methad mast exten&@ w r t i n the Udtrrd States for exploratio~ md edwtim of wanhi &pod&. dammow lop, C o r n r n d j suppkrnentd with a singbz-pobt msfstailee log, m t l y supply about 80 percent of the bask data for om regerve c W t i o R a d mu& of the w ~ k r 6 . p ~ &ngk inf~nnatio~ Tmck-mounted 'rotmy eqnipmcnt i s EMhmody emphy&& holes usually hwre a nominai b

3

Tool development and application: pressure, temperature, spectral gamma ray logging of the SB-15 well  

DOE Green Energy (OSTI)

Sandia`s involvement with downhole instrumentation dates from the mid 1970s when work was centered on the development of a high-temperature acoustic borehole televiewer, and the establishment of a list of high- temperature component parts such as resistors, integrated circuits, and sensors. This work evolved into the development of memory logging devices for the US Continental Scientific Drilling Program. These tools were of low cost and very easy to use. Their deployment resulted in scientific advancement in understanding geothermal formations, and a thrust of the current program is to move memory tools from the scientific realm to the commercial environment. The tools developed and utilized in the SB-15 well among other field tests are completely self- contained in that power is obtained from batteries and data are stored in an electronic memory system. Three memory tools form the backbone of the initial Sandia tool suite. Pressure/temperature measurements are necessary for the evaluation of geothermal reservoirs, and they are relatively simple to make. Thus, the initial Sandia program concentrated on such a tool, and it has been successfully used in SB-15. This tool will form the basis for future tools since many engineering principles were proven in its evolution. This pressure/temperature tool combination is very useful in characterizing the geothermal reservoir. Another tool in the Sandia suite measures the natural gamma rays from the formation. This spectral gamma ray tool is useful in defining lithology, paleoflows, and certain clays. SB-15 well logging history and a preliminary interpretation of the data is presented in this report.

Sattler, A.R.; Norman, R.; Henfling, J.A.

1996-12-01T23:59:59.000Z

4

A Brief Review of the Basis for, and the Procedures Currently Utilized in, Gross Gamma-Ray Log Calibration (October 1976)  

Energy.gov (U.S. Department of Energy (DOE))

A Brief Review of the Basis for, and the Procedures Currently Utilized in, Gross Gamma-Ray Log Calibration (October 1976)

5

Laser System for Livermore's Mono Energetic Gamma-Ray Source  

SciTech Connect

A Mono-energetic Gamma-ray (MEGa-ray) source, based on Compton scattering of a high-intensity laser beam off a highly relativistic electron beam, requires highly specialized laser systems. To minimize the bandwidth of the {gamma}-ray beam, the scattering laser must have minimal bandwidth, but also match the electron beam depth of focus in length. This requires a {approx}1 J, 10 ps, fourier-transform-limited laser system. Also required is a high-brightness electron beam, best provided by a photoinjector. This electron source requires a second laser system with stringent requirements on the beam including flat transverse and longitudinal profiles and fast rise times. Furthermore, these systems must be synchronized to each other with ps-scale accuracy. Using a novel hyper-dispersion compressor configuration and advanced fiber amplifiers and diode-pumped Nd:YAG amplifiers, we have designed laser systems that meet these challenges for the X-band photoinjector and Compton-scattering source being built at Lawrence Livermore National Laboratory.

Gibson, D; Albert, F; Bayramian, A; Marsh, R; Messerly, M; Ebbers, C; Hartemann, F

2011-03-14T23:59:59.000Z

6

Gamma Ray Array Detector Trigger Sub-System  

E-Print Network (OSTI)

Gamma Ray Array Detector (GRAD) is one of External Target Facility (ETF) subsystems at the Heavy Ion Research Facility at Lanzhou. The trigger subsystem of the GRAD has been developed based on Field Programmable Gate Array (FPGAs) and PXI interface. The GRAD trigger subsystem makes prompt L1 trigger decisions to select valid events. These decisions are made by processing the hit signals from 1024 CsI scintillators of the GRAD. According to the physical requirements, the GRAD trigger subsystem generates 12-bit trigger signals that are passed to the ETF global trigger system. In addition, the GRAD trigger subsystem generates trigger data that are packed and transmitted to the host computer via PXI bus for off-line analysis. The trigger processing is implemented in the front-end electronics and one FPGA of the trigger module. The logic of PXI transmission and reconfiguration is implemented in the other FPGA of the trigger module. The reliable and efficient performance in the Gamma-ray experiments demonstrates that the GRAD trigger subsystem is capable to satisfy the physical requirements.

Du Zhong-Wei; Su Hong; Qian Yi; Kong Jie

2012-11-06T23:59:59.000Z

7

Neutron interrogation system using high gamma ray signature to detect contraband special nuclear materials in cargo  

DOE Patents (OSTI)

A system for inspecting cargo for the presence of special nuclear material. The cargo is irradiated with neutrons. The neutrons produce fission products in the special nuclear material which generate gamma rays. The gamma rays are detecting indicating the presence of the special nuclear material.

Slaughter, Dennis R. (Oakland, CA); Pohl, Bertram A. (Berkeley, CA); Dougan, Arden D. (San Ramon, CA); Bernstein, Adam (Palo Alto, CA); Prussin, Stanley G. (Kensington, CA); Norman, Eric B. (Oakland, CA)

2008-04-15T23:59:59.000Z

8

Short Gamma Ray Bursts as possible electromagnetic counterpart of coalescing binary systems  

E-Print Network (OSTI)

Coalescing binary systems, consisting of two collapsed objects, are among the most promising sources of high frequency gravitational waves signals detectable, in principle, by ground-based interferometers. Binary systems of Neutron Star or Black Hole/Neutron Star mergers should also give rise to short Gamma Ray Bursts, a subclass of Gamma Ray Bursts. Short-hard-Gamma Ray Bursts might thus provide a powerful way to infer the merger rate of two-collapsed object binaries. Under the hypothesis that most short Gamma Ray Bursts originate from binaries of Neutron Star or Black Hole/Neutron Star mergers, we outline here the possibility to associate short Gamma Ray Bursts as electromagnetic counterpart of coalescing binary systems.

S. Capozziello; M. De Laurentis; I. De Martino; M. Formisano

2010-04-27T23:59:59.000Z

9

Radiation detection system for portable gamma-ray spectroscopy  

DOE Patents (OSTI)

A portable gamma ray detection apparatus having a gamma ray detector encapsulated by a compact isolation structure having at least two volumetrically-nested enclosures where at least one is a thermal shield. The enclosures are suspension-mounted to each other to successively encapsulate the detector without structural penetrations through the thermal shields. A low power cooler is also provided capable of cooling the detector to cryogenic temperatures without consuming cryogens, due to the heat load reduction by the isolation structure and the reduction in the power requirements of the cooler. The apparatus also includes a lightweight portable power source for supplying power to the apparatus, including to the cooler and the processing means, and reducing the weight of the apparatus to enable handheld operation or toting on a user's person.

Rowland, Mark S. (Alamo, CA); Howard, Douglas E. (Livermore, CA); Wong, James L. (Dublin, CA); Jessup, James L. (Tracy, CA); Bianchini, Greg M. (Livermore, CA); Miller, Wayne O. (Livermore, CA)

2006-06-20T23:59:59.000Z

10

Semantic image interpretation of gamma ray profiles in petroleum exploration  

Science Conference Proceedings (OSTI)

This paper presents the S-Chart framework, an approach for semantic image interpretation of line charts; and the InteliStrata system, an application for semantic interpretation of gamma ray profiles. The S-Chart framework is structured as a set of knowledge ... Keywords: Gamma ray well log, Ontology, Semantic image interpretation, Stratigraphy, Symbol grounding problem, Visual knowledge

Sandro Rama Fiorini; Mara Abel; Claiton M. S. Scherer

2011-04-01T23:59:59.000Z

11

Real time method and computer system for identifying radioactive materials from HPGe gamma-ray spectroscopy  

DOE Patents (OSTI)

A real-time method and computer system for identifying radioactive materials which collects gamma count rates from a HPGe gamma-radiation detector to produce a high-resolution gamma-ray energy spectrum. A library of nuclear material definitions ("library definitions") is provided, with each uniquely associated with a nuclide or isotope material and each comprising at least one logic condition associated with a spectral parameter of a gamma-ray energy spectrum. The method determines whether the spectral parameters of said high-resolution gamma-ray energy spectrum satisfy all the logic conditions of any one of the library definitions, and subsequently uniquely identifies the material type as that nuclide or isotope material associated with the satisfied library definition. The method is iteratively repeated to update the spectrum and identification in real time.

Rowland, Mark S. (Alamo, CA); Howard, Douglas E. (Livermore, CA); Wong, James L. (Dublin, CA); Jessup, James L. (Tracy, CA); Bianchini, Greg M. (Livermore, CA); Miller, Wayne O. (Livermore, CA)

2007-10-23T23:59:59.000Z

12

A Mobile High Resolution Gamma Ray Spectrometry System for Radiological Surveys  

Science Conference Proceedings (OSTI)

Surveying nuclear power plant sites for radioactive contamination is an expensive part of the overall decommissioning process. This report details a mobile radiological survey system designed to produce a rapid and cost effective radiological characterization of outdoor land areas. The system combines high resolution gamma ray spectrometry with modern automated surveying techniques to precisely locate areas of contamination.

1998-12-04T23:59:59.000Z

13

DEVELOPMENT OF DEPOSIT DETECTION SYSTEM IN PIPELINES OF THE STEELWORKS USING CS-137 GAMMA-RAY  

SciTech Connect

The deposit is built up in the pipeline of the steelworks by the chemical reaction among COG (coke oven gas), BFG (blast furnace gas), moisture, and steel in the high temperature environment and obstructs the smooth gas flow. In this study a gamma-ray system is developed to detect the deposit accumulated in pipelines and calculate the accumulation rate with respect to the cross section area of pipes. Cs-137 is used as the gamma-ray source and the system is designed to apply to pipes of various diameters. This system also includes the DB for storage and display of the measurement results so that it can be used for the efficient management of the pipelines.

Song, Won-Joon; Lee, Seung-Hee; Jeong, Hee-Dong [Research Institute of Industrial Science and Technology, 32 Hyoja-Dong, Nam-Ku, Pohang, 790-330 (Korea, Republic of)

2008-02-28T23:59:59.000Z

14

Massive Stars in Colliding Wind Systems: the High-Energy Gamma-Ray Perspective  

SciTech Connect

Colliding winds of massive stars in binary systems are viable candidates for non-thermal high-energy photon emission. Long since, coincidences between massive star systems/associations and {gamma}-ray sources have been noted. Now, with the sensitivity of the Fermi Gamma Ray Observatory and current very-high-energy (VHE) Cherenkov instruments, will it be possible to sensibly probe these systems as high-energy emitters.We will summarize the characteristics and broadband predictions of generic optically thin emission models in the observables accessible at GeV and TeV energies. The ability to constrain orbital parameters of massive star-star binaries through GeV-to-TeV observations is discussed. As an example we will present orbital parameter constraints for the nearby Wolf-Rayet binary system WR 147 based on recently published VHE flux limits. Combining our broadband emission model with the cataloged binaries systems and their individual parameters allows us to conclude on the population of massive star-star systems at high-energy {gamma}-rays.

Reimer, Anita; Reimer, Olaf; /Stanford U., HEPL /KIPAC, Menlo Park

2011-11-23T23:59:59.000Z

15

Gadolinium-doped water cerenkov-based neutron and high energy gamma-ray detector and radiation portal monitoring system  

Science Conference Proceedings (OSTI)

A water Cerenkov-based neutron and high energy gamma ray detector and radiation portal monitoring system using water doped with a Gadolinium (Gd)-based compound as the Cerenkov radiator. An optically opaque enclosure is provided surrounding a detection chamber filled with the Cerenkov radiator, and photomultipliers are optically connected to the detect Cerenkov radiation generated by the Cerenkov radiator from incident high energy gamma rays or gamma rays induced by neutron capture on the Gd of incident neutrons from a fission source. The PMT signals are then used to determine time correlations indicative of neutron multiplicity events characteristic of a fission source.

Dazeley, Steven A; Svoboda, Robert C; Bernstein, Adam; Bowden, Nathaniel

2013-02-12T23:59:59.000Z

16

X-ray and gamma ray detector readout system  

DOE Patents (OSTI)

A readout electronics scheme is under development for high resolution, compact PET (positron emission tomography) imagers based on LSO (lutetium ortho-oxysilicate, Lu.sub.2SiO.sub.5) scintillator and avalanche photodiode (APD) arrays. The key is to obtain sufficient timing and energy resolution at a low power level, less than about 30 mW per channel, including all required functions. To this end, a simple leading edge level crossing discriminator is used, in combination with a transimpedance preamplifier. The APD used has a gain of order 1,000, and an output noise current of several pA/ Hz, allowing bipolar technology to be used instead of CMOS, for increased speed and power efficiency. A prototype of the preamplifier and discriminator has been constructed, achieving timing resolution of 1.5 ns FWHM, 2.7 ns full width at one tenth maximum, relative to an LSO/PMT detector, and an energy resolution of 13.6% FWHM at 511 keV, while operating at a power level of 22 mW per channel. Work is in progress towards integration of this preamplifier and discriminator with appropriate coincidence logic and amplitude measurement circuits in an ASIC suitable for a high resolution compact PET instrument. The detector system and/or ASIC can also be used for many other applications for medical to industrial imaging.

Tumer, Tumay O (Riverside, CA); Clajus, Martin (Los Angeles, CA); Visser, Gerard (Bloomington, IN)

2010-10-19T23:59:59.000Z

17

A technical review of the SWEPP gamma-ray spectrometer system  

Science Conference Proceedings (OSTI)

The SWEPP Gamma-ray Spectrometer (SGRS) was developed by INEL researchers as a nonintrusive method of determining the isotopic ratios of TRU and U materials in a 208-liter waste drums. The SGRS has been in use at SWEPP since mid-1994. Enough questions have been raised regarding the system reliability and technical capabilities, that, coupled with a desire to procure an additional gamma-ray spectroscopy system in order to increase the drum throughput of SWEPP, have prompted an independent technical review of the SGRS. The author was chosen as the reviewer, and this report documents the results of the review. While the SGRS is accurate in its isotopic ratio results, the system is not calculationally robust. The primary reason for this lack of calculational reliability is the implementation of the attenuation corrections. Suggested changes may improve the system reliability dramatically. The SGRS is a multiple detector spectrometry system. Tests were conducted on various methods for combining the four detector results into a single drum representative value. No clear solution was reached for the cases in which the isotopic ratios are vertically segregated; however, some methods showed promise. These should be investigated further. 14 refs. , 15 figs., 23 tabs.

Hartwell, J.K.

1996-03-01T23:59:59.000Z

18

The drive system of the Major Atmospheric Gamma-ray Imaging Cherenkov Telescope  

E-Print Network (OSTI)

The MAGIC telescope is an imaging atmospheric Cherenkov telescope, designed to observe very high energy gamma-rays while achieving a low energy threshold. One of the key science goals is fast follow-up of the enigmatic and short lived gamma-ray bursts. The drive system for the telescope has to meet two basic demands: (1) During normal observations, the 72-ton telescope has to be positioned accurately, and has to track a given sky position with high precision at a typical rotational speed in the order of one revolution per day. (2) For successfully observing GRB prompt emission and afterglows, it has to be powerful enough to position to an arbitrary point on the sky within a few ten seconds and commence normal tracking immediately thereafter. To meet these requirements, the implementation and realization of the drive system relies strongly on standard industry components to ensure robustness and reliability. In this paper, we describe the mechanical setup, the drive control and the calibration of the pointing, as well as present measurements of the accuracy of the system. We show that the drive system is mechanically able to operate the motors with an accuracy even better than the feedback values from the axes. In the context of future projects, envisaging telescope arrays comprising about 100 individual instruments, the robustness and scalability of the concept is emphasized.

T. Bretz; D. Dorner; R. M. Wagner; P. Sawallisch

2008-10-27T23:59:59.000Z

19

An Analysis of a Spreader Bar Crane Mounted Gamma-Ray Radiation Detection System  

E-Print Network (OSTI)

Over 95% of imports entering the United States from outside North America arrive via cargo containers by sea at 329 ports of entry. The current layered approach for the detection only scans 5% of cargo bound for the United States. This is inadequate to protect our country. This research involved the building of a gamma-ray radiation detection system used for cargo scanning. The system was mounted on a spreader bar crane (SBC) at the Port of Tacoma (PoT) and the applicability and capabilities of the system were analyzed. The detection system provided continuous count rate and spectroscopic data among three detectors while operating in an extreme environment. In a separate set of experiments, 60Co and 137Cs sources were positioned inside a cargo container and data were recorded for several count times. The Monte Carlo N-Particle (MCNP) code was used to simulate a radioactive source inside an empty cargo container and the results were compared to experimentally recorded data. The detection system demonstrated the ability to detect 60Co, 137Cs, 192Ir, highly-enriched uranium (HEU), and weapons-grade plutonium (WGPu) with minimum detectable activities (MDA) of 5.9 ± 0.4 microcuries (?Ci), 19.3 ± 1.1 ?Ci, 11.7 ± 0.6 ?Ci, 3.5 ± 0.3 kilograms (kg), and 30.6 ± 1.3 grams (g), respectively. This system proved strong gamma-ray detection capabilities, but was limited in the detection of fissile materials Additional details of this system are presented and advantages of this approach to cargo scanning over current approaches are discussed.

Grypp, Matthew D

2013-05-01T23:59:59.000Z

20

Decision support system based on hierarchical co-evolutionary fuzzy approach: A case study in detecting gamma ray signals  

Science Conference Proceedings (OSTI)

Decision support systems are powerful technologies for complex decision making and problem solving. However, constructing an accurate and interpretable decision support system (DSS) for any domain is a challenge. In this paper, a novel hierarchical co-evolutionary ... Keywords: ANFIS, Co-evolutionary learning, DENFIS, Decision support system, Fuzzy system, Genetic algorithm, HiCEFS, Hierarchical co-evolutionary fuzzy system, High-energy gamma rays, TSK

H. Huang; M. Pasquier; C. Quek

2011-09-01T23:59:59.000Z

Note: This page contains sample records for the topic "gamma-ray logging systems" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


21

Determining the Impact of Concrete Roadways on Gamma Ray Background Readings for Radiation Portal Monitoring Systems  

E-Print Network (OSTI)

The dissolution of the Soviet Union coupled with the growing sophistication of international terror organizations has brought about a desire to ensure that a sound infrastructure exists to interdict smuggled nuclear material prior to leaving its country of origin. To combat the threat of nuclear trafficking, radiation portal monitors (RPMs) are deployed around the world to intercept illicit material while in transit by passively detecting gamma and neutron radiation. Portal monitors in some locations have reported abnormally high gamma background count rates. The higher background data has been attributed, in part, to the concrete surrounding the portal monitors. Higher background can ultimately lead to more material passing through the RPMs undetected. This work is focused on understanding the influence of the concrete surrounding the monitors on the total gamma ray background for the system. This research employed a combination of destructive and nondestructive analytical techniques with computer simulations to form a model that may be adapted to any RPM configuration. Six samples were taken from three different composition concrete slabs. The natural radiologcal background of these samples was determined using a high-purity germanium (HPGe) detector in conjunction with the Canberra In-Situ Object Counting System (ISOCS™) and Genie™ 2000 software packages. The composition of each sample was determined using thermal and fast neutron activation analysis (NAA) techniques. The results from these experiments were incorporated into a Monte Carlo N-Particle (MNCP) photon transport simulation to determine the expected gamma ray count rate in the RPM due to the concrete. The results indicate that a quantitative estimate may be possible if the experimental conditions are optimized to eliminate sources of uncertainty. Comparisons of actual and simulated count rate data for 137Cs check sources showed that the model was accurate to within 15%. A comparison of estimated and simulated count rates in one concrete slab showed that the model was accurate to within 4%. Subsequent sensitivity analysis showed that if the elemental concentrations are well known, the carbon and hydrogen content could be easily estimated. Another sensitivity analysis revealed that the small fluctuations in density have a minimal impact on the gamma count rate. The research described by this thesis provides a method by which RPM end users may quantitatively estimate the expected gamma background from concrete foundations beneath the systems. This allows customers to adjust alarm thresholds to compensate for the elevated background due to the concrete, thereby increasing the probability of intercepting illicit radiological and nuclear material.

Ryan, Christopher Michael

2011-05-01T23:59:59.000Z

22

Gamma-ray bursts and other sources of giant lightning discharges in protoplanetary systems  

E-Print Network (OSTI)

Lightning in the solar nebula is considered to be one of the probable sources for producing the chondrules that are found in meteorites. Gamma-ray bursts (GRBs) provide a large flux of gamma-rays that Compton scatter and create a charge separation in the gas because the electrons are displaced from the positive ions. The electric field easily exceeds the breakdown value of ~1 V m^-1 over distances of order 0.1 AU. The energy in a giant lightning discharge exceeds a terrestrial lightning flash by a factor of ~10^12. The predicted post-burst emission of gamma-rays from accretion into the newly formed black hole or spin-down of the magnetar is sufficiently intense to cause a lightning storm in the nebula that lasts for days and is more probable than the GRB because the radiation is beamed into a larger solid angle. The giant outbursts from nearby soft gamma-ray repeater sources (SGRs) are also capable of causing giant lightning discharges. The total amount of chondrules produced is in reasonable agreement with the observations of meteorites. Furthermore in the case of GRBs most chondrules were produced in a few major melting events by nearby GRBs and lightning occurred at effectively the same time over the whole nebula, and provide accurate time markers to the formation of chondrules and evolution of the solar nebula. This model provides a reasonable explanation for the delay between the formation of calcium aluminium inclusions (CAIs) and chondrules.

B. McBreen; E. Winston; S. McBreen; L. Hanlon

2005-02-01T23:59:59.000Z

23

High spatial resolution X-ray and gamma ray imaging system using diffraction crystals  

DOE Patents (OSTI)

A method and a device for high spatial resolution imaging of a plurality of sources of x-ray and gamma-ray radiation are provided. The device comprises a plurality of arrays, with each array comprising a plurality of elements comprising a first collimator, a diffracting crystal, a second collimator, and a detector.

Smither, Robert K. (Hinsdale, IL)

2011-05-17T23:59:59.000Z

24

A celestial gamma-ray foreground due to the albedo of small solar system bodies and a remote probe of the interstellar cosmic ray spectrum  

E-Print Network (OSTI)

We calculate the gamma-ray albedo flux from cosmic-ray (CR) interactions with the solid rock and ice in Main Belt asteroids (MBAs), Jovian and Neptunian Trojan asteroids, and Kuiper Belt objects (KBOs) using the Moon as a template. We show that the gamma-ray albedo for the Main Belt, Trojans, and Kuiper Belt strongly depends on the small-body size distribution of each system. Based on an analysis of the Energetic Gamma Ray Experiment Telescope (EGRET) data we infer that the diffuse emission from the MBAs, Trojans, and KBOs has an integrated flux of less than ~6x10^{-6} cm^{-2} s^{-1} (100-500 MeV), which corresponds to ~12 times the Lunar albedo, and may be detectable by the forthcoming Gamma Ray Large Area Space Telescope (GLAST). If detected by GLAST, it can provide unique direct information about the number of small bodies in each system that is difficult to assess by any other method. Additionally, the KBO albedo flux can be used to probe the spectrum of CR nuclei at close-to-interstellar conditions. The orbits of MBAs, Trojans, and KBOs are distributed near the ecliptic, which passes through the Galactic center and high Galactic latitudes. Therefore, the asteroid gamma-ray albedo has to be taken into account when analyzing weak gamma-ray sources close to the ecliptic, especially near the Galactic center and for signals at high Galactic latitudes, such as the extragalactic gamma-ray emission. The asteroid albedo spectrum also exhibits a 511 keV line due to secondary positrons annihilating in the rock. This may be an important and previously unrecognized celestial foreground for the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) observations of the Galactic 511 keV line emission including the direction of the Galactic center.

Igor V. Moskalenko; Troy A. Porter; Seth W. Digel; Peter F. Michelson; Jonathan F. Ormes

2007-12-12T23:59:59.000Z

25

Gamma ray detector shield  

DOE Patents (OSTI)

A gamma ray detector shield comprised of a rigid, lead, cylindrical-shaped vessel having upper and lower portions with an pneumatically driven, sliding top assembly. Disposed inside the lead shield is a gamma ray scintillation crystal detector. Access to the gamma detector is through the sliding top assembly.

Ohlinger, R.D.; Humphrey, H.W.

1985-08-26T23:59:59.000Z

26

Gamma-ray Astronomy  

E-Print Network (OSTI)

The relevance of gamma-ray astronomy to the search for the origin of the galactic and, to a lesser extent, the ultra-high-energy cosmic rays has long been recognised. The current renaissance in the TeV gamma-ray field has resulted in a wealth of new data on galactic and extragalactic particle accelerators, and almost all the new results in this field were presented at the recent International Cosmic Ray Conference (ICRC). Here I summarise the 175 papers submitted on the topic of gamma-ray astronomy to the 30th ICRC in Merida, Mexico in July 2007.

Hinton, Jim

2007-01-01T23:59:59.000Z

27

Gamma-ray Astronomy  

E-Print Network (OSTI)

The relevance of gamma-ray astronomy to the search for the origin of the galactic and, to a lesser extent, the ultra-high-energy cosmic rays has long been recognised. The current renaissance in the TeV gamma-ray field has resulted in a wealth of new data on galactic and extragalactic particle accelerators, and almost all the new results in this field were presented at the recent International Cosmic Ray Conference (ICRC). Here I summarise the 175 papers submitted on the topic of gamma-ray astronomy to the 30th ICRC in Merida, Mexico in July 2007.

Jim Hinton

2007-12-20T23:59:59.000Z

28

Gamma Ray Pulsars: Observations  

E-Print Network (OSTI)

High-energy gamma rays are a valuable tool for studying particle acceleration and radiation in the magnetospheres of energetic pulsars. The six or more pulsars seen by CGRO/EGRET show that: the light curves usually have double-peak structures (suggesting a broad cone of emission); gamma rays are frequently the dominant component of the radiated power; and all the spectra show evidence of a high-energy turnover. Unless a new pulsed component appears at higher energies, progress in gamma-ray pulsar studies will be greatest in the 1-20 GeV range. Ground-based telescopes whose energy ranges extend downward toward 10 GeV should make important measurements of the spectral cutoffs. The Gamma-ray Large Area Space Telescope (GLAST), now in planning for a launch in 2005, will provide a major advance in sensitivity, energy range, and sky coverage.

David J. Thompson

2001-01-03T23:59:59.000Z

29

Gamma-Ray Bursts  

E-Print Network (OSTI)

Gamma-ray bursts are the most luminous explosions in the Universe, and their origin and mechanism are the focus of intense research and debate. More than three decades after their discovery, and after pioneering breakthroughs from space and ground experiments, their study is entering a new phase with the recently launched Swift satellite. The interplay between these observations and theoretical models of the prompt gamma ray burst and its afterglow is reviewed.

P. Meszaros

2006-05-09T23:59:59.000Z

30

Gamma-ray events thunderclouds  

E-Print Network (OSTI)

Andromeda: A mission to determine the gamma-ray burst distance scale F.A. Harrison, W.R. Cook, T was submitted to the STEDI program, and will also be proposed as a NASA Small Explorer. Keywords: bursts, gamma-rays, small missions 1 SCIENTIFIC OBJECTIVES 1.1 Gamma-ray Bursts Gamma-ray bursts GRBs were discovered

California at Berkeley, University of

31

Probing the Pulsar Wind in the gamma-ray Binary System PSR B1259-63/SS 2883  

E-Print Network (OSTI)

The spectral energy distribution from the X-ray to the very high energy regime ($>100$ GeV) has been investigated for the $\\gamma$-ray binary system PSR B1259-63/SS2883 as a function of orbital phase within the framework of a simple model of a pulsar wind nebula. The emission model is based on the synchrotron radiation process for the X-ray regime and the inverse Compton scattering process boosting stellar photons from the Be star companion to the very high energy (100GeV-TeV) regime. With this model, the observed temporal behavior can, in principle, be used to probe the pulsar wind properties at the shock as a function of the orbital phase. Due to theoretical uncertainties in the detailed microphysics of the acceleration process and the conversion of magnetic energy into particle kinetic energy, the observed X-ray data for the entire orbit are fit using two different methods.

Takata, Jumpei

2009-01-01T23:59:59.000Z

32

A ground level gamma-ray burst observed in association with rocket-triggered lightning  

E-Print Network (OSTI)

ray bursts which BeppoSAX satellite detected with one arcminute accuracy. 3 VHE GAMMA RAY EMISSION 1111111111111111111111111111111111111111111111111111111111111111111111111111111111111 (d) 30 20 10 0 -10 1051520 ActiveGalacticNuclei Log(Sizer(cm)) SuperNova Explosion GammaRayBurst@icrr.u-tokyo.ac.jp ABSTRACT Copious production of electrons and positrons results in very high energy gamma-rays from

Slatton, Clint

33

The Ptolemaic Gamma-Ray Burst Universe  

E-Print Network (OSTI)

The BATSE experiment on GRO has demonstrated the isotropic arrival directions and flat log N vs. log S of cosmic gamma-ray bursts. These data are best explained if the burst sources are distributed throughout an extended spherical Galactic halo, as previously suggested by Jennings. The halo’s radius is at least 40 Kpc, and probably is more than 100 Kpc. I consider possible origins of this halo, including primordial formation and neutron stars recoiling from their birthplaces in the Galactic disc. A simple geometrical model leads to a predicted relation between the dipole and quadrupole anisotropy. I suggest that neutron stars born with low recoil become millisecond pulsars, while those born with high recoil become the sources of gamma-ray bursts; these populations are nearly disjoint. Quiescent counterparts of gamma-ray bursts are predicted to be undetectably faint. 2 The first results from the BATSE on GRO (BATSE Science Team 1991) have revived the question of the distribution of gamma-ray burst sources in space. Their chief results, isotropy of gamma-ray burst directions and a log N vs. log S slope significantly flatter than-1.5, confirm earlier reports (see, for example, Meegan, Fishman and Wilson 1985 and the review by Cline 1984). Questions of relative calibration of different instruments and the paucity of good directional data permitted skepticism in the past. Such skepticism is no longer tenable, and the theoretical questions raised earlier must be faced. An isotropic distribution of sources implies that, out to the maximum distance of observation permitted by instrumental sensitivity, all directions contain equivalent source populations. The source population for an observed flux or fluence S is expressed as the integral N ( ˆ ? ?, S) =

J. I. Katz

1992-01-01T23:59:59.000Z

34

Leak checker data logging system  

DOE Patents (OSTI)

A portable, high speed, computer-based data logging system for field testing systems or components located some distance apart employs a plurality of spaced mass spectrometers and is particularly adapted for monitoring the vacuum integrity of a long string of a superconducting magnets such as used in high energy particle accelerators. The system provides precise tracking of a gas such as helium through the magnet string when the helium is released into the vacuum by monitoring the spaced mass spectrometers allowing for control, display and storage of various parameters involved with leak detection and localization. A system user can observe the flow of helium through the magnet string on a real-time basis hour the exact moment of opening of the helium input valve. Graph reading can be normalized to compensate for magnet sections that deplete vacuum faster than other sections between testing to permit repetitive testing of vacuum integrity in reduced time.

Payne, J.J.; Gannon, J.C.

1994-12-31T23:59:59.000Z

35

Leak checker data logging system  

DOE Patents (OSTI)

A portable, high speed, computer-based data logging system for field testing systems or components located some distance apart employs a plurality of spaced mass spectrometers and is particularly adapted for monitoring the vacuum integrity of a long string of a superconducting magnets such as used in high energy particle accelerators. The system provides precise tracking of a gas such as helium through the magnet string when the helium is released into the vacuum by monitoring the spaced mass spectrometers allowing for control, display and storage of various parameters involved with leak detection and localization. A system user can observe the flow of helium through the magnet string on a real-time basis hour the exact moment of opening of the helium input valve. Graph reading can be normalized to compensate for magnet sections that deplete vacuum faster than other sections between testing to permit repetitive testing of vacuum integrity in reduced time.

Gannon, Jeffrey C. (Arlington, TX); Payne, John J. (Waterman, IL)

1996-01-01T23:59:59.000Z

36

Leak checker data logging system  

DOE Patents (OSTI)

A portable, high speed, computer-based data logging system for field testing systems or components located some distance apart employs a plurality of spaced mass spectrometers and is particularly adapted for monitoring the vacuum integrity of a long string of a superconducting magnets such as used in high energy particle accelerators. The system provides precise tracking of a gas such as helium through the magnet string when the helium is released into the vacuum by monitoring the spaced mass spectrometers allowing for control, display and storage of various parameters involved with leak detection and localization. A system user can observe the flow of helium through the magnet string on a real-time basis hour the exact moment of opening of the helium input valve. Graph reading can be normalized to compensate for magnet sections that deplete vacuum faster than other sections between testing to permit repetitive testing of vacuum integrity in reduced time. 18 figs.

Gannon, J.C.; Payne, J.J.

1996-09-03T23:59:59.000Z

37

Gamma Ray Bursts  

E-Print Network (OSTI)

Gamma-ray bursts have been detected at photon energies up to tens of GeV. We review some recent developments in the X-ray to GeV photon phenomenology in the light of Swift and Fermi observations, and some of the theoretical models developed to explain them, with a view towards implications for C.T.A.

Peter Mészáros

2012-04-09T23:59:59.000Z

38

Gamma Ray Bursts Sudden, intense flashes of gamma rays  

E-Print Network (OSTI)

. Sakamoto1,12 , C. L. Sarazin13 , P. Schady6,10 , M. Stamatikos1,12 & S. E. Woosley14 Gamma-ray bursts (GRBs. Identification of two classes of gamma-ray bursts. Astrophys. J. 413, L101­L104 (1993). 2. Fruchter, A. et al). 3. Woosley, S. E. Gamma-ray bursts from stellar mass accretion disks around black holes. Astrophys

Washington at Seattle, University of - Department of Physics, Electroweak Interaction Research Group

39

Gamma-ray burst populations.  

E-Print Network (OSTI)

??Over the last fifty years the field of gamma-ray bursts has shown incredible growth, but the amassing of data has also left observers and theorists… (more)

Virgili, Francisco J.

2011-01-01T23:59:59.000Z

40

Gamma Ray Pulsars: Multiwavelength Observations  

E-Print Network (OSTI)

High-energy gamma rays are a valuable tool for studying particle acceleration and radiation in the magnetospheres of energetic pulsars. The seven or more pulsars seen by instruments on the Compton Gamma Ray Observatory (CGRO) show that: the light curves usually have double-peak structures (suggesting a broad cone of emission); gamma rays are frequently the dominant component of the radiated power; and all the spectra show evidence of a high-energy turnover. For all the known gamma-ray pulsars, multiwavelength observations and theoretical models based on such observations offer the prospect of gaining a broad understanding of these rotating neutron stars. The Gamma-ray Large Area Space Telescope (GLAST), now in planning for a launch in 2007, will provide a major advance in sensitivity, energy range, and sky coverage.

David J. Thompson

2003-12-10T23:59:59.000Z

Note: This page contains sample records for the topic "gamma-ray logging systems" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


41

Energetics of Gamma Ray Bursts  

E-Print Network (OSTI)

We determine the distribution of total energy emitted by gamma-ray bursts for bursts with fluences and distance information. Our core sample consists of eight bursts with BATSE spectra and spectroscopic redshifts. We extend this sample by adding four bursts with BATSE spectra and host galaxy R magnitudes. From these R magnitudes we calculate a redshift probability distribution; this method requires a model of the host galaxy population. From a sample of ten bursts with both spectroscopic redshifts and host galaxy R magnitudes (some do not have BATSE spectra) we find that the burst rate is proportional to the galaxy luminosity at the epoch of the burst. Assuming that the total energy emitted has a log-normal distribution, we find that the average emitted energy (assumed to be radiated isotropically) is $gamma iso} > = 1.3^{+1.2}_{-1.0} \\times 10^{53}$ ergs (for H$_0$ = 65 km s$^{-1}$ Mpc$^{-1}$, $\\Omega_m=0.3$ and $\\Omega_\\Lambda=0.7$); the distribution has a logarithmic width of $\\sigma_\\gamma=1.7^{+0.7}_{-0.3}$. The corresponding distribution of X-ray afterglow energy (for seven bursts) has $ = 4.0^{+1.6}_{-1.8} \\times 10^{51}$ergs and $\\sigma_X = 1.3^{+0.4}_{-0.3}$. For completeness, we also provide spectral fits for all bursts with BATSE spectra for which there were afterglow searches.

Raul Jimenez; David Band; Tsvi Piran

2001-03-16T23:59:59.000Z

42

Distributed Control System Log-Keeping Specification  

Science Conference Proceedings (OSTI)

Information generated within the distributed control system (DCS) at most fossil generating stations could be more fully used by converting relevant information into searchable operator logs. This can be done through automated techniques combined with operator oversight and review. As a result, operator log-keeping effectiveness can be greatly improved while reducing the burden on the operator.ObjectivesThis project was undertaken to create specifications for ...

2012-12-12T23:59:59.000Z

43

Gamma-Ray Burst Lines  

E-Print Network (OSTI)

The evidence for spectral features in gamma-ray bursts is summarized. As a guide for evaluating the evidence, the properties of gamma-ray detectors and the methods of analyzing gamma-ray spectra are reviewed. In the 1980's, observations indicated that absorption features below 100 keV were present in a large fraction of bright gamma-ray bursts. There were also reports of emission features around 400 keV. During the 1990's the situation has become much less clear. A small fraction of bursts observed with BATSE have statistically significant low-energy features, but the reality of the features is suspect because in several cases the data of the BATSE detectors appear to be inconsistent. Furthermore, most of the possible features appear in emission rather than the expected absorption. Analysis of data from other instruments has either not been finalized or has not detected lines.

Michael S. Briggs

1999-10-20T23:59:59.000Z

44

Modeling gamma-ray bursts.  

E-Print Network (OSTI)

??Discovered serendipitously in the late 1960s, gamma-ray bursts (GRBs) are huge explosions of energy that happen at cosmological distances. They provide a grand physical playground… (more)

Maxham, Amanda

2011-01-01T23:59:59.000Z

45

Gamma Ray Bursts and CETI  

E-Print Network (OSTI)

Gamma ray burst sources are isotropically distributed. They could be located at distances $\\sim 1000$ AU. (Katz \\cite{JK92}) GRB signals have many narrow peaks that are unresolved at the millisecond time resolution of existing observations. \\cite{JK87} CETI could use stars as gravitational lenses for interstellar gamma ray laser beam communication. Much better time resolution of GRB signals could rule out (or confirm?) the speculative hypothesis that GRB = CETI.

Frank D. Smith Jr

1993-02-10T23:59:59.000Z

46

Gamma ray bursts ROBERT S MACKAY  

E-Print Network (OSTI)

Gamma ray bursts ROBERT S MACKAY COLIN ROURKE We propose that a gamma ray burst is a kinematic Gamma ray bursts are intense flashes of electromagnetic radiation of cosmic origin lasting from ten accepted mechanism. We propose that a gamma ray burst is simply a kinematic effect, namely the effect

Rourke, Colin

47

Locating TeV Gamma-Ray Sources with Sub-Arcminute Precision: the Pointing Calibration of the HEGRA System of Imaging Atmospheric Cherenkov Telescopes  

E-Print Network (OSTI)

Stereoscopic viewing of TeV gamma-ray air showers with systems of Imaging Atmospheric Cherenkov Telescopes (IACTs) allows to reconstruct the origin of individual primary particles with an accuracy of 0.1 degree or better. The shower impact point can be determined within 15 meters. To actually achieve this resolution, the pointing of the telescopes of an IACT system needs to be controlled with high precision. For the HEGRA IACT system, a procedure to calibrate telescope pointing was established, using bright stars distributed over the sky as references. On the basis of these measurements, one determines parameters of a correction function which is valid for the complete hemisphere. After correction a pointing accuracy of 0.01 degree is achieved.

G. Puehlhofer; A. Daum; G. Hermann; M. Hess; W. Hofmann; C. Koehler; M. Panter

1998-01-12T23:59:59.000Z

48

Gamma-RayGamma-Ray Bursts: from SwiftBursts: from Swift  

E-Print Network (OSTI)

Gamma-RayGamma-Ray Bursts: from SwiftBursts: from Swift to GLASTto GLAST Bing ZhangBing ZhangGehrels, et al), et al) #12;Gamma-ray bursts: the mostGamma-ray bursts: the most violent explosions Bursts Apparently high gamma-ray efficiency. Highly magnetized flow? Roming et al., 2005 #12;Surprises

California at Santa Cruz, University of

49

LIGHT CURVES OF SWIFT GAMMA RAY BURSTS  

E-Print Network (OSTI)

Recent observations from the Swift gamma-ray burst mission indicate that a fraction of gamma ray bursts are characterized by a canonical behaviour of the X-ray afterglows. We present an effective theory which allows us to account for X-ray light curves of both (short- long) gamma ray bursts and X-ray rich flashes. We propose that gamma ray bursts originate from massive magnetic powered pulsars. Subject headings: gamma-rays: bursts 1.

Paolo Cea

2006-01-01T23:59:59.000Z

50

THE GAMMA-RAY BURST MYSTERY  

E-Print Network (OSTI)

Gamma-ray bursts are transient events from beyond the solar system. Besides the allure of their mysterious origin, bursts are physically fascinating because they undoubtedly require exotic physics. Optical transients coincident with burst positions show that some, and probably all, bursts originate at cosmological distances, and not from a large Galactic halo. Observations of these events ’ spectral and temporal behavior will guide and constrain the study of the physical processes producing this extragalactic phenomenon. 1

David L. Band

1997-01-01T23:59:59.000Z

51

Real time gamma-ray signature identifier  

DOE Patents (OSTI)

A real time gamma-ray signature/source identification method and system using principal components analysis (PCA) for transforming and substantially reducing one or more comprehensive spectral libraries of nuclear materials types and configurations into a corresponding concise representation/signature(s) representing and indexing each individual predetermined spectrum in principal component (PC) space, wherein an unknown gamma-ray signature may be compared against the representative signature to find a match or at least characterize the unknown signature from among all the entries in the library with a single regression or simple projection into the PC space, so as to substantially reduce processing time and computing resources and enable real-time characterization and/or identification.

Rowland, Mark (Alamo, CA); Gosnell, Tom B. (Moraga, CA); Ham, Cheryl (Livermore, CA); Perkins, Dwight (Livermore, CA); Wong, James (Dublin, CA)

2012-05-15T23:59:59.000Z

52

Neutrinos from Gamma Ray Bursts  

E-Print Network (OSTI)

We show that the detection of neutrinos from a typical gamma ray burst requires a kilometer-scale detector. We argue that large bursts should be visible with the neutrino telescopes under construction. We emphasize the 3 techniques by which neutrino telescopes can perform this search: by triggering on i) bursts of muons from muon neutrinos, ii) muons from air cascades initiated by high energy gamma rays and iii) showers made by relatively low energy ($\\simeq 100\\,\\mev$) electron neutrinos. Timing of neutrino-photon coincidences may yield a measurement of the neutrino mass to order $10^{-5}$~eV, an interesting range in light of the solar neutrino anomaly.

F. Halzen; G. Jaczko

1996-02-07T23:59:59.000Z

53

Gamma ray astrophysics: the EGRET results  

E-Print Network (OSTI)

Cosmic gamma rays provide insight into some of the most dynamic processes in the Universe. At the dawn of a new generation of gamma-ray telescopes, this review summarizes results from the Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory, the principal predecessor mission studying high-energy photons in the 100 MeV energy range. EGRET viewed a gamma-ray sky dominated by prominent emission from the Milky Way, but featuring an array of other sources, including quasars, pulsars, gamma-ray bursts, and many sources that remain unidentified. A central feature of the EGRET results was the high degree of variability seen in many gamma-ray sources, indicative of the powerful forces at work in objects visible to gamma-ray telescopes.

D J Thompson

2008-11-05T23:59:59.000Z

54

Light Curves of Swift Gamma Ray Bursts  

E-Print Network (OSTI)

Recent observations from the Swift gamma-ray burst mission indicate that a fraction of gamma ray bursts are characterized by a canonical behaviour of the X-ray afterglows. We present an effective theory which allows us to account for X-ray light curves of both (short - long) gamma ray bursts and X-ray rich flashes. We propose that gamma ray bursts originate from massive magnetic powered pulsars.

Paolo Cea

2006-06-05T23:59:59.000Z

55

Stellar Sources of Gamma-ray Bursts  

E-Print Network (OSTI)

Correlation analysis of Swift gamma-ray burst coordinates and nearby star locations (catalog Gliese) reveals 4 coincidences with good angular accuracy. The random probability is 4\\times 10^{-5}, so evidencing that coincident stars are indeed gamma-ray burst sources. Some additional search of stellar gamma-ray bursts is discussed.

Luchkov, B I

2011-01-01T23:59:59.000Z

56

Fermi Observations of Gamma?ray Bursts  

Science Conference Proceedings (OSTI)

The gamma?ray emission mechanism of Gamma?ray bursts (GRBs) are still unknown. Fermi Gamma?ray Space Telescope successfully detected high?energy (> 100 MeV) emission from 17 GRBs since its launch. Fermi revealed the distinct temporal behaviors and extra spectral component from high?energy emission. These new observational results are driving many theoretical implications

Masanori Ohno; The Fermi?LAT collaborations; The GBM collaborations

2010-01-01T23:59:59.000Z

57

Multifrequency Observations of Gamma-Ray Burst  

E-Print Network (OSTI)

Neither a flaring nor a quiescent counterpart to a gamma-ray burst has yet been convincingly identified at any wavelength region. The present status of the search for counterparts of classical gamma-ray bursts is given. Particular emphasis is put on the search for flaring counterparts, i.e. emission during or shortly after the gamma-ray emission.

J. Greiner

1995-10-04T23:59:59.000Z

58

The Diverse Environments of Gamma-Ray Bursts  

E-Print Network (OSTI)

of a Very Bright Gamma- Ray Burst in a Galactic Halo 3.1Galaxies of Dark Gamma-Ray Bursts: Observational Constraints1.3 Gamma-Ray Burst Classi?cation . . . . . . 1.4 Gamma-Ray

Perley, Daniel Alan

2011-01-01T23:59:59.000Z

59

Neutrinos from Gamma Ray Bursts  

E-Print Network (OSTI)

The observed fluxes of cosmic rays and gamma rays are used to infer the maximum allowed high-energy neutrino flux allowed for Gamma Ray Bursts (GRBs), following Mannheim, Protheroe, and Rachen (2000). It is shown that if GRBs produce the ultrahigh-energy cosmic rays, they should contribute (a) at least 10% of the extragalactic gamma ray background between 3 MeV and 30 GeV, contrary to their observed energy flux which is only a minute fraction of this flux, and (b) a cumulative neutrino flux a factor of 20 below the AMANDA (Neutrino 2000) limit on isotropic neutrinos. This could have two implications, either GRBs do not produce the ultrahigh energy cosmic rays or that the GRBs are strongly beamed and emit most of their power at energies well above 100 GeV implausibly increasing the energy requirements, but consistent with the marginal detections of a few low-redshift GRBs by MILAGRITO, HEGRA-AIROBICC, and the Tibet-Array. All crucial measurements to test the models will be available in the next few years. These are measurements of (i) high-energy neutrinos with AMANDA-ICECUBE or an enlarged ANTARES/NESTOR ocean detector, (ii) GRB redshifts from HETE-2 follow-up studies, and (iii) GRB spectra above 10 GeV with low-threshold imaging air Cherenkov telescopes such as MAGIC and the space telescopes AGILE and GLAST.

Karl Mannheim

2000-10-18T23:59:59.000Z

60

Gamma-Ray Bursts observed by INTEGRAL  

E-Print Network (OSTI)

During the first six months of operations, six Gamma Ray Bursts (GRBs) have been detected in the field of view of the INTEGRAL instruments and localized by the INTEGRAL Burst Alert System (IBAS): a software for the automatic search of GRBs and the rapid distribution of their coordinates. I describe the current performances of IBAS and review the main results obtained so far. The coordinates of the latest burst localized by IBAS, GRB 031203, have been distributed within 20 s from the burst onset and with an uncertainty radius of only 2.7 arcmin.

S. Mereghetti

2003-12-12T23:59:59.000Z

Note: This page contains sample records for the topic "gamma-ray logging systems" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


61

Gamma Ray Burst Central Engines  

E-Print Network (OSTI)

I review aspects of the theory of long-duration gamma-ray burst (GRB) central engines. I focus on the requirements of any model; these include the angular momentum of the progenitor, the power, Lorentz factor, asymmetry, and duration of the flow, and both the association and the non-association with bright supernovae. I compare and contrast the collapsar and millisecond proto-magnetar models in light of these requirements. The ability of the latter model to produce a flow with Lorentz factor ~100 while simultaneously maintaining a kinetic luminosity of ~10^50 ergs/s for a timescale of ~10-100 s is emphasized.

Todd A. Thompson

2008-07-04T23:59:59.000Z

62

Black Stars and Gamma Ray Bursts  

E-Print Network (OSTI)

Stars that are collapsing toward forming a black hole but are frozen near the Schwarzschild horizon are termed ``black stars''. Collisions of black stars, in contrast to black hole collisions, may be sources of gamma ray bursts, whose basic parameters are estimated quite simply and are found to be consistent with observed gamma ray bursts. Black star gamma ray bursts should be preceded by gravitational wave emission similar to that from the coalescence of black holes.

Tanmay Vachaspati

2007-06-08T23:59:59.000Z

63

Gamma ray burst outflows and afterglows.  

E-Print Network (OSTI)

?? We carry out a theoretical investigation of jet propagation in Gamma Ray Bursts and examine the jitter radiation mechanism as a means of producing… (more)

Morsony, Brian J.

2009-01-01T23:59:59.000Z

64

Search for gamma ray burst counterparts  

Science Conference Proceedings (OSTI)

The confident detection of a Gamma Ray Burst counterpart would likely provide the much needed breakthrough in our understanding of the cause and site of bursts. As such

Bradley E. Schaefer

1994-01-01T23:59:59.000Z

65

Pulsed Photofission Delayed Gamma Ray Detection for Nuclear Material Identification  

SciTech Connect

Innovative systems with increased sensitivity and resolution are in great demand to detect diversion and to prevent misuse in support of nuclear materials management for the U.S. fuel cycle. Nuclear fission is the most important multiplicative process involved in non-destructive active interrogation. This process produces the most easily recognizable signature for nuclear materials. High-energy gamma rays can also excite a nucleus and cause fission through a process known as photofission. After photofission reactions, delayed signals are easily distinguishable from the interrogating radiation. Linac-based, advanced inspection techniques utilizing the fission signals after photofission have been extensively studied for homeland security applications. Previous research also showed that a unique delayed gamma ray energy spectrum exists for each fissionable isotope. Isotopic composition measurement methods based on delayed gamma ray spectroscopy will be the primary focus of this work.

John Kavouras; Xianfei Wen; Daren R. Norman; Dante R. Nakazawa; Haori Yang

2012-11-01T23:59:59.000Z

66

Pulser injection with subsequent removal for gamma-ray spectrometry  

DOE Patents (OSTI)

An improved system for gamma-ray spectroscopy characterized by an interface module that controls the injection of electronic pulses as well as separation logic that enables storage of pulser events in a region of the spectrum of a multichannel analyzer distinct from the region reserved for storage of gamma-ray events. The module accomplishes this by tagging pulser events (high or low) injected into the amplification circuitry, adding an offset to the events so identified at the time the events are at the output of the analog to digital converter, and storing such events in the upper portion of the spectrum stored in the multichannel analyzer. The module can be adapted for use with existing gamma-ray spectroscopy equipment to provide for automatic analyses of radioisotopes. 7 figs.

Hartwell, J.K.; Goodwin, S.G.; Johnson, L.O.; Killian, E.W.

1989-02-01T23:59:59.000Z

67

Gravitational Waves versus X and Gamma Ray Emission in a Short Gamma-Ray Burst  

E-Print Network (OSTI)

The recent progress in the understanding the physical nature of neutron star equilibrium configurations and the first observational evidence of a genuinely short gamma-ray burst, GRB 090227B, allows to give an estimate of the gravitational waves versus the X and Gamma ray emission in a short gamma-ray burst.

F. G. Oliveira; Jorge A. Rueda; Remo Ruffini

2012-05-31T23:59:59.000Z

68

The Universe Viewed in Gamma-Rays 1 Properties of Gamma-ray Bursts Localized by  

E-Print Network (OSTI)

The short gamma-ray burst ­ SGR giant flare connection Kevin Hurley University of California cosmic gamma-ray bursts. There are at least two general ways to approach this problem. One is statistical short gamma-ray bursts (GRBs) could actually be extragalactic giant magnetar flares is not new by any

Enomoto, Ryoji

69

Gamma-Ray Pulsar Visibility  

E-Print Network (OSTI)

PSR J0437-4715 is a millisecond pulsar (MSP) thought to be ``pair formation starved'' (having limited pair cascades due to magnetic photon absorption). Fortunately the general relativistic (GR) electrodynamical model under consideration applicable to this pulsar have few free parameters. We model PSR J0437-4715's visibility, using a 3D model which incorporates the variation of the GR E-field over the polar cap (PC), taking different observer and inclination angles into account. Using this pulsar as a case study, one may generalize to conducting a pulsar population visibility study. We lastly comment on the role of the proposed South African SKA (Square Kilometre Array) prototype, KAT (Karoo Array Telescope), for GLAST gamma-ray pulsar identification.

Venter, C

2005-01-01T23:59:59.000Z

70

Gamma-Ray Pulsar Visibility  

E-Print Network (OSTI)

PSR J0437-4715 is a millisecond pulsar (MSP) thought to be ``pair formation starved'' (having limited pair cascades due to magnetic photon absorption). Fortunately the general relativistic (GR) electrodynamical model under consideration applicable to this pulsar have few free parameters. We model PSR J0437-4715's visibility, using a 3D model which incorporates the variation of the GR E-field over the polar cap (PC), taking different observer and inclination angles into account. Using this pulsar as a case study, one may generalize to conducting a pulsar population visibility study. We lastly comment on the role of the proposed South African SKA (Square Kilometre Array) prototype, KAT (Karoo Array Telescope), for GLAST gamma-ray pulsar identification.

C. Venter; O. C. de Jager; A. Tiplady

2005-10-14T23:59:59.000Z

71

Real-Time System Log Monitoring/Analytics Framework  

SciTech Connect

Analyzing system logs provides useful insights for identifying system/application anomalies and helps in better usage of system resources. Nevertheless, it is simply not practical to scan through the raw log messages on a regular basis for large-scale systems. First, the sheer volume of unstructured log messages affects the readability, and secondly correlating the log messages to system events is a daunting task. These factors limit large-scale system logs primarily for generating alerts on known system events, and post-mortem diagnosis for identifying previously unknown system events that impacted the systems performance. In this paper, we describe a log monitoring framework that enables prompt analysis of system events in real-time. Our web-based framework provides a summarized view of console, netwatch, consumer, and apsched logs in real- time. The logs are parsed and processed to generate views of applications, message types, individual/group of compute nodes, and in sections of the compute platform. Also from past application runs we build a statistical profile of user/application characteristics with respect to known system events, recoverable/non-recoverable error messages and resources utilized. The web-based tool is being developed for Jaguar XT5 at the Oak Ridge Leadership Computing facility.

Oral, H Sarp [ORNL; Dillow, David A [ORNL; Park, Byung H [ORNL; Shipman, Galen M [ORNL; Geist, Al [ORNL; Gunasekaran, Raghul [ORNL

2011-01-01T23:59:59.000Z

72

CONSTRAINTS ON VERY HIGH ENERGY GAMMA-RAY EMISSION FROM GAMMA-RAY BURSTS R. Atkins,1,2  

E-Print Network (OSTI)

CONSTRAINTS ON VERY HIGH ENERGY GAMMA-RAY EMISSION FROM GAMMA-RAY BURSTS R. Atkins,1,2 W. Benbow,3 emission from gamma-ray bursts (GRBs) during the prompt emission phase. Detection of >100 GeV counterparts on potential GRB models. Subject headinggs: gamma rays: bursts -- gamma rays: observations 1. INTRODUCTION

California at Santa Cruz, University of

73

Gamma-ray decay schemes for $sup 93$Kr, $sup 93$Rb, and $sup 93$Sr  

SciTech Connect

A study of the gamma-ray de-excitation following the beta decays of $sup 93$Kr, $sup 93$Rb, and $sup 93$Sr using the TRISTAN on-line separator facility is reported. Gamma-ray singles and gamma-gamma coincidence measurements were made using Ge(Li) detectors. Of the 162 gamma rays observed in the decay of $sup 93$Sr, 143, representing more than 99 percent of the total gamma-ray intensity observed, were placed in a level scheme containing 36 levels. For the decay of $sup 93$Rb, 243 gamma rays were observed, of which 231 are placed in a level scheme consisting of 74 levels. This again represents a placement of over 99 percent of the total gamma-ray intensity measured. In the case of the $sup 93$Kr decay approximately 98.5 percent of the observed gamma-ray intensity has been accounted for by the proposed level scheme. This results from the placement of 203 of the 217 gamma rays assigned to this decay in a level scheme comprising 56 levels. Beta-branching for these decays were determined from transition intensity balances. Spin and parity assignments were proposed, whenever possible, on the basis of gamma-ray transition probabilities and deduced log ft values. A comparison is made with the available reaction data for the $sup 93$Y level scheme. In all cases an attempt has been made to explain some of the levels in terms of the nuclear shell model and decay systematics. 18 figures, 20 tables, 68 references. (auth)

Bischof, C.J.

1976-01-01T23:59:59.000Z

74

Observations of Gamma-Ray Bursts at Extreme Energies  

E-Print Network (OSTI)

of Gamma-Ray Bursts . . . . . . . . . . . . . Redshift-CRUZ OBSERVATIONS OF GAMMA-RAY BURSTS AT EXTREME ENERGIES ADedication xix Acknowledgments xx 1 Gamma-Ray Bursts 1.1

Aune, Taylor

2012-01-01T23:59:59.000Z

75

Neutrino production in nucleonic interactions in gamma-ray bursters  

E-Print Network (OSTI)

Neutrinos produced in gamma-ray bursters (GRBers) may provide a unique probe for the physics of these extreme astrophysical systems. Here we discuss neutrino production in inelastic neutron-proton collisions within the relativistic outflows associated with GRBers. We consider both the widely used fireball model and a recently proposed magneto-hydrodynamic (MHD) model for the GRB outflow.

Hylke B. J. Koers

2008-05-16T23:59:59.000Z

76

Gamma-ray Bursts and their Central Engines  

E-Print Network (OSTI)

Gamma-ray bursts are the most luminous and probably the most relativistic events in the universe. The last few years have seen a tremendous increase in our knowledge of these events, but the source of the bursts still remains elusive. I will summarise recent progress in this field with special emphasis on our understanding of the possible progenitor systems.

Stephan Rosswog

2004-01-04T23:59:59.000Z

77

The Swift Gamma-Ray Burst Mission  

E-Print Network (OSTI)

The Swift mission, scheduled for launch in early 2004, is a multiwavelength observatory for gamma-ray burst (GRB) astronomy. It is the first-of-its-kind autonomous rapid-slewing satellite for transient astronomy and pioneers the way for future rapid-reaction and multiwavelength missions. It will be far more powerful than any previous GRB mission, observing more than 100 bursts per year and performing detailed X-ray and UV/optical afterglow observations spanning timescales from 1 minute to several days after the burst. The objectives are to determine the origin of GRBs; classify GRBs and search for new types; study the interaction of the ultra-relativistic outflows of GRBs with their surrounding medium; and use GRBs to study the early universe out to z>10. The mission is being developed by a NASA-led international collaboration. It will carry three instruments: a new-generation wide-field gamma-ray (15-150 keV) detector; a narrow-field X-ray telescope; and a narrow-field UV/optical telescope. Redshift determinations will be made for most bursts. In addition to the primary GRB science, the mission will perform a hard X-ray survey to a sensitivity of ~1 mCrab (~2x10^{-11} erg cm^{-2} s^{-1} in the 15-150 keV band), more than an order of magnitude better than HEAO A-4. A flexible data and operations system will allow rapid follow-up observations of all types of high-energy transients, with rapid data downlink and uplink available through the NASA TDRSS system. The mission is currently funded for 2 years of operations and the spacecraft will have a lifetime to orbital decay of ~8 years. [ABRIDGED

N. Gehrels; G Chincarini; P. Giommi; K. O. Mason; J. A. Nousek; A. A. Wells; N. E. White; S. D. Barthelmy; D. N. Burrows; L. R. Cominsky; K. C. Hurley; F. E. Marshall; P. Meszaros; P. W. A. Roming; Swift Science Team

2004-05-12T23:59:59.000Z

78

SLAC National Accelerator Laboratory - Fermi's Latest Gamma-ray...  

NLE Websites -- All DOE Office Websites (Extended Search)

Fermi's Latest Gamma-ray Census Highlights Cosmic Mysteries By Francis Reddy, NASAGoddard Space Flight Center September 9, 2011 Every three hours, NASA's Fermi Gamma-ray Space...

79

Gamma-Ray Burst Physics with GLAST  

SciTech Connect

The Gamma-ray Large Area Space Telescope (GLAST) is an international space mission that will study the cosmos in the energy range 10 keV-300 GeV, the upper end of which is one of the last poorly observed region of the celestial electromagnetic spectrum. The ancestor of the GLAST/LAT was the Energetic Gamma Ray Experiment Telescope (EGRET) detector, which flew onboard the Compton Gamma Ray Observatory (CGRO). The amount of information and the step forward that the high energy astrophysics made thanks to its 9 years of observations are impressive. Nevertheless, EGRET uncovered the tip of the iceberg, raising many questions, and it is in the light of EGRET's results that the great potential of the next generation gamma-ray telescope can be appreciated. GLAST will have an imaging gamma-ray telescope, the Large Area Telescope (LAT) vastly more capable than instruments own previously, as well as a secondary instrument, the GLAST Bursts Monitor, or GBM, to augment the study of gamma-ray bursts. Gamma-Ray Bursts (GRBs) science is one of the most exciting challenges for the GLAST mission, exploring the high energy emission of one of the most intense phenomena in the sky, shading light on various problems: from the acceleration of particles to the emission processes, to more exotic physics like Quantum Gravity effect. In this paper we report the work done so far in the simulation development as well as the study of the LAT sensitivity to GRB.

Omodei, N.; /INFN, Pisa

2006-10-06T23:59:59.000Z

80

Gamma-Ray Bursts and Particle Astrophysics  

E-Print Network (OSTI)

Gamma-ray bursts are violent events occurring randomly in the sky. In this review, I will present the fireball model, proposed to explain the phenomenon of gamma-ray bursts. This model has important consequences for the production and observation at Earth of gravitational waves, high energy neutrinos, cosmic rays and high energy photons, and the second part of this review will be focused on these aspects. A last section will briefly discuss the topic of the use of gamma-ray bursts as standard candles and possible cosmological studies.

B. Gendre

2008-07-24T23:59:59.000Z

Note: This page contains sample records for the topic "gamma-ray logging systems" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


81

Mining Gamma-Ray Burst Data  

E-Print Network (OSTI)

Gamma-ray bursts provide what is probably one of the messiest of all astrophysical data sets. Burst class properties are indistinct, as overlapping characteristics of individual bursts are convolved with effects of instrumental and sampling biases. Despite these complexities, data mining techniques have allowed new insights to be made about gamma-ray burst data. We demonstrate how data mining techniques have simultaneously allowed us to learn about gamma-ray burst detectors and data collection, cosmological effects in burst data, and properties of burst subclasses. We discuss the exciting future of this field, and the web-based tool we are developing (with support from the NASA AISR Program). We invite others to join us in AI-guided gamma-ray burst classification (http://grb.mnsu.edu/grb/).

Jon Hakkila; Richard J. Roiger; David J. Haglin; Robert S. Mallozzi; Geoffrey N. Pendleton; Charles A. Meegan

2000-11-30T23:59:59.000Z

82

Gravitational waves and gamma-ray bursts  

E-Print Network (OSTI)

Gamma-Ray Bursts are likely associated with a catastrophic energy release in stellar mass objects. Electromagnetic observations provide important, but indirect information on the progenitor. On the other hand, gravitational waves emitted from the central source, carry direct information on its nature. In this context, I give an overview of the multi-messenger study of gamma-ray bursts that can be carried out by using electromagnetic and gravitational wave observations. I also underline the importance of joint electromagnetic and gravitational wave searches, in the absence of a gamma-ray trigger. Finally, I discuss how multi-messenger observations may probe alternative gamma-ray burst progenitor models, such as the magnetar scenario.

Alessandra Corsi; for the LIGO Scientific Collaboration; for the Virgo Collaboration

2012-04-18T23:59:59.000Z

83

Gamma-Ray Pulsar Studies with GLAST  

E-Print Network (OSTI)

Some pulsars have their maximum observable energy output in the gamma-ray band, offering the possibility of using these high-energy photons as probes of the particle acceleration and interaction processes in pulsar magnetospheres. After an extended hiatus between satellite missions, the recently-launched AGILE mission and the upcoming Gamma-ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT) will allow gamma-ray tests of the theoretical models developed based on past discoveries. With its greatly improved sensitivity, better angular resolution, and larger energy reach than older instruments, GLAST LAT should detect dozens to hundreds of new gamma-ray pulsars and measure luminosities, light curves, and phase-resolved spectra with unprecedented resolution. It will also have the potential to find radio-quiet pulsars like Geminga, using blind search techniques. Cooperation with radio and X-ray pulsar astronomers is an important aspect of the LAT team's planning for pulsar studies.

D. J. Thompson

2007-11-27T23:59:59.000Z

84

Current Topics in Gamma-Ray Astrophysics  

Science Conference Proceedings (OSTI)

... into e+–e– pairs ends up as rays. Figure 1 shows a calculation of -ray burst luminosity as ... The integrated energy in gamma-rays from the calculated ...

2000-03-14T23:59:59.000Z

85

Gamma-Ray Pulsar Studies With GLAST  

SciTech Connect

Some pulsars have their maximum observable energy output in the gamma-ray band, offering the possibility of using these high-energy photons as probes of the particle acceleration and interaction processes in pulsar magnetospheres. After an extended hiatus between satellite missions, the recently-launched AGILE mission and the upcoming Gamma-ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT) will allow gamma-ray tests of the theoretical models developed based on past discoveries. With its greatly improved sensitivity, better angular resolution, and larger energy reach than older instruments, GLAST LAT should detect dozens to hundreds of new gamma-ray pulsars and measure luminosities, light curves, and phase-resolved spectra with unprecedented resolution. It will also have the potential to find radio-quiet pulsars like Geminga, using blind search techniques. Cooperation with radio and X-ray pulsar astronomers is an important aspect of the LAT team's planning for pulsar studies.

Thompson, D.J.; /NASA, Goddard

2011-11-23T23:59:59.000Z

86

Gravitational waves and short gamma ray bursts.  

E-Print Network (OSTI)

??Short hard gamma-ray bursts (GRB) are believed to be produced by compact binary coalescences (CBC) { either double neutron stars or neutron star{black hole binaries.… (more)

Predoi, Valeriu

2012-01-01T23:59:59.000Z

87

Studying Gamma Ray Bursts from a  

E-Print Network (OSTI)

Studying Gamma Ray Bursts from a new perspective! {... Unraveling some mysteries and adding new Radio Op0cal X-ray Short ( energy -ray photons... ... accompained by a considerable long las0ng emission

Â?umer, Slobodan

88

Diffuse gamma-rays from galactic halos  

E-Print Network (OSTI)

Here we review our current knowledge on diffuse gamma-rays from galactic halos. Estimates of the relative contribution of the various emission processes at low and high latitudes are compared to the data over 6 decades in energy. The observed spectral shape differs from what was expected, especially at ver low and very high energies. In the latter case, above 1 GeV, the sky emission related to gas exceeds the expected pi^0 decay spectrum. At energies below 1 MeV the relatively high gamma-ray intensity indicates at high density of nearly relativistic electrons which would have a strong influence on the energy and ionisation balance of the interstellar medium. Given the EGRET results for the Magellanic Clouds the gamma-ray emissivity in the outer halo is probably small, so that a substantial amount of baryonic dark matter may be hidden at 20-50 kpc radius without inducing observable gamma-ray emission.

M. Pohl

1996-03-12T23:59:59.000Z

89

Can gamma-ray bursts constrain quintessence?  

E-Print Network (OSTI)

Using the narrow clustering of the geometrically corrected gamma-ray energies released by gamma-ray bursts, we investigate the possibility of using these sources as standard candles to probe cosmological parameters such as the matter density Omega_m and the cosmological constant energy density Omega_Lambda. By simulating different samples of gamma-ray bursts, we find that Omega_m can be determined with accuracy ~7% with data from 300 sources. We also show that, if Omega = 1 is due to a quintessence field, some of the models proposed in the literature may be discriminated from a Universe with cosmological constant, by a similar-sized sample of gamma-ray bursts.

T. Di Girolamo; R. Catena; M. Vietri; G. Di Sciascio

2005-04-27T23:59:59.000Z

90

Gamma Ray Bursts from Ordinary Cosmic Strings  

E-Print Network (OSTI)

We give an upper estimate for the number of gamma ray bursts from ordinary (non-superconducting) cosmic strings expected to be observed at terrestrial detectors. Assuming that cusp annihilation is the mechanism responsible for the bursts we consider strings arising at a GUT phase transition and compare our estimate with the recent BATSE results. Further we give a lower limit for the effective area of future detectors designed to detect the cosmic string induced flux of gamma ray bursts.

R. H. Brandenberger; A. T. Sornborger; M. Trodden

1993-02-12T23:59:59.000Z

91

Unidentified Gamma-Ray Sources and Microquasars  

E-Print Network (OSTI)

Some phenomenological properties of the unidentified EGRET detections suggest that there are two distinct groups of galactic gamma-ray sources that might be associated with compact objects endowed with relativistic jets. We discuss different models for gamma-ray production in both microquasars with low- and high-mass stellar companions. We conclude that the parent population of low-latitude and halo variable sources might be formed by yet undetected microquasars and microblazars.

G. E. Romero; I. A Grenier; M. M. Kaufman Bernado; I. F. Mirabel; D. F. Torres

2004-02-12T23:59:59.000Z

92

Theoretical Models of Gamma-Ray Bursts  

E-Print Network (OSTI)

Models of gamma ray bursts are reviewed in the light of recent observations of afterglows which point towards a cosmological origin. The physics of fireball shock models is discussed, with attention to the type of light histories and spectra during the gamma-ray phase. The evolution of the remnants and their afterglows is considered, as well as their implications for our current understanding of the mechanisms giving rise to the bursts.

P. Meszaros

1997-11-28T23:59:59.000Z

93

Gamma-ray albedo of the moon  

E-Print Network (OSTI)

We use the GEANT4 Monte Carlo framework to calculate the gamma-ray albedo of the Moon due to interactions of cosmic ray (CR) nuclei with moon rock. Our calculation of the albedo spectrum agrees with the EGRET data. We show that the spectrum of gamma rays from the Moon is very steep with an effective cutoff around 4 GeV (600 MeV for the inner part of the Moon disc). Apart from other astrophysical sources, the albedo spectrum of the Moon is well understood, including its absolute normalisation; this makes it a useful "standard candle" for gamma-ray telescopes, such as the forthcoming Gamma Ray Large Area Space Telescope (GLAST). The albedo flux depends on the incident CR spectrum which changes over the solar cycle. Therefore, it is possible to monitor the CR spectrum using the albedo gamma-ray flux. Simultaneous measurements of CR proton and helium spectra by the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA), and observations of the albedo gamma rays by the GLAST Large Area Telescope (LAT), can be used to test the model predictions and will enable the GLAST LAT to monitor the CR spectrum near the Earth beyond the lifetime of PAMELA.

Igor V. Moskalenko; Troy A. Porter

2007-05-25T23:59:59.000Z

94

Results from the Milagro Gamma-Ray Observatory  

E-Print Network (OSTI)

V energies, and a search for transient emission above 100 GeV from gamma-ray bursts. 1 Introduction remnants and gamma-ray bursts (GRB). Gamma rays are also produced when high-energy cosmic rays interactResults from the Milagro Gamma-Ray Observatory E. Blaufuss for the Milagro Collaboration a,1 , a

California at Santa Cruz, University of

95

Are There MeV Gamma-Ray Bursts?  

E-Print Network (OSTI)

It is often stated that gamma-ray bursts (GRBs) have typical energies of several hundred keV. Is this a real feature of GRBs or is it due to an observational bias? We consider the possibility that bursts of a given bolometric luminosity occur with a hardness distribution $p(H)d \\log H \\propto H^\\gamma d \\log H$. We model the detection efficiency of BATSE as a function of $H$ and calculate the expected distribution of $H$ in the observed sample for various values of $\\gamma$. We show that because the detection efficiency of BATSE falls steeply with increasing $H$, the paucity of hard bursts need not be real. We find that the observed sample is consistent with a distribution above $H = 100$ keV with $\\gamma \\approx 0$ or even $\\gamma =0.5$. Thus, a large population of unobserved hard gamma-ray bursts may exist. It is important to extend the present analysis to a larger sample of BATSE bursts and to include the OSSE and COMPTEL limits. If the full sample is consistent with $\\gamma\\ \\sgreat\\ 0$, then it would be interesting to look for MeV bursts in the future.

Tsvi Piran; Ramesh Narayan

1995-12-19T23:59:59.000Z

96

Fireball/Blastwave Model and Soft Gamma-ray Repeaters  

E-Print Network (OSTI)

Soft gamma-ray repeaters are at determined distances and their positions are known accurately. If observed, afterglows from their soft gamma-ray bursts will provide important clues to the study of the so called "classical gamma-ray bursts". On applying the popular fireball/blastwave model of classical gamma-ray bursts to soft gamma-ray repeaters, it is found that their X-ray and optical afterglows are detectable. Monitoring of the three repeaters is solicited.

Y. F. Huang; Z. G. Dai; T. Lu

1998-10-28T23:59:59.000Z

97

A Gamma-Ray Burst Trigger Toolkit  

E-Print Network (OSTI)

The detection rate of a gamma-ray burst detector can be increased by using a count rate trigger with many accumulation times ?t and energy bands ?E. Because a burst’s peak flux varies when averaged over different ?t and ?E, the nominal sensitivity (the numerical value of the peak flux) of a trigger system is less important than how much fainter a burst could be at the detection threshold as ?t and ?E are changed. The relative sensitivity of different triggers can be quantified by referencing the detection threshold back to the peak flux for a fiducial value of ?t and ?E. This mapping between peak flux values for different sets of ?t and ?E varies from burst to burst. Quantitative estimates of the burst detection rate for a given detector and trigger system can be based on the observed rate at a measured peak flux value in this fiducial trigger. Predictions of a proposed trigger’s burst detection rate depend on the assumed burst population, and these predictions can be wildly in error for triggers that differ significantly from previous missions. I base the fiducial rate on the BATSE observations: 550 bursts per sky above a peak flux of 0.3 ph cm ?2 s ?1 averaged over ?t=1.024 s and ?E=50–300 keV. Using a sample of 100 burst lightcurves I find that triggering on all possible values of ?t that are multiples of 0.064 s decreases the average threshold peak flux on the 1.024 s timescale by a factor of 0.6. Extending ?E to lower energies includes the large flux of the X-ray background, increasing the background count rate. Consequently a low energy ?E is advantageous only for very soft bursts. Whether a large fraction of the population of bright bursts is soft is disputed; the new population of X-ray Flashes is soft but relatively faint. Subject headings: gamma-rays: bursts

unknown authors

2002-01-01T23:59:59.000Z

98

Real-Time Optical Flux Limits From Gamma-Ray Bursts Measured By The GROCSE Experiment  

E-Print Network (OSTI)

The Gamma-Ray Optical Counterpart Search Experiment (GROCSE) presents new experimental upper limits on the optical flux from gamma-ray bursts (GRBs). Our experiment consisted of a fully-automated very wide-field opto-electronic detection system that imaged locations of GRBs within a few seconds of receiving trigger signals provided by BATSE’s real-time burst coordinate distribution network (BACODINE). The experiment acquired 3800 observing hours, recording 22 gamma-ray burst triggers within ?30 s of the start of the burst event. Some of these bursts were imaged while gamma-ray radiation was being detected by BATSE. We identified no optical counterparts associated with gamma-ray bursts amongst these events at the mV ? 7.0 to 8.5 sensitivity level. We find the ratio of the upper limit to the V-band optical flux, F?, to the gamma-ray fluence, ??, from these data to be 2 × 10?18 gamma rays: bursts – 3 – 1.

H. S. Park; E. Ables; S. D. Barthelmy; R. M. Bionta; P. S. Butterworth; T. L. Cline; D. H. Ferguson; G. J. Fishman; N. Gehrels; K. Hurley; C. Kouveliotou; B. C. Lee; C. A. Meegan; L. L. Ott; E. L. Parker Received Accepted

1997-01-01T23:59:59.000Z

99

CANGAROO-III OBSERVATION OF TeV GAMMA RAYS FROM THE VICINITY OF PSR B1706-44  

Science Conference Proceedings (OSTI)

Observation by the CANGAROO-III stereoscopic system of the Imaging Cherenkov Telescope has detected extended emission of TeV gamma rays in the vicinity of the pulsar PSR B1706-44. The strength of the signal observed as gamma-ray-like events varies when we apply different ways of emulating background events. The reason for such uncertainties is argued in relevance to gamma rays embedded in the 'OFF-source data', that is, unknown sources and diffuse emission in the Galactic plane, namely, the existence of a complex structure of TeV gamma-ray emission around PSR B1706-44.

Enomoto, R.; Kifune, T. [Institute for Cosmic Ray Research, University of Tokyo, Kashiwa, Chiba 277-8582 (Japan); Kushida, J.; Hattori, T.; Ishioka, H.; Kawachi, A. [Department of Physics, Tokai University, Hiratsuka, Kanagawa 259-1292 (Japan); Nakamori, T. [Department of Basic Physics, Tokyo Institute of Technology, Meguro, Tokyo, 152-8551 (Japan); Bicknell, G. V. [Research School of Astronomy and Astrophysics, Australian National University, ACT 2611 (Australia); Clay, R. W. [School of Chemistry and Physics, University of Adelaide, SA 5005 (Australia); Edwards, P. G. [Narrabri Observatory of the Australia Telescope National Facility, CSIRO, Epping, NSW 2121 (Australia); Gunji, S.; Inoue, K. [Department of Physics, Yamagata University, Yamagata 990-8560 (Japan); Hara, S. [Ibaraki Prefectural University of Health Sciences, Ami, Ibaraki 300-0394 (Japan); Hara, T. [Faculty of Management Information, Yamanashi Gakuin University, Kofu, Yamanashi 400-8575 (Japan); Hayashi, S.; Kajino, F. [Department of Physics, Konan University, Kobe, Hyogo 658-8501 (Japan); Higashi, Y.; Kabuki, S. [Department of Physics, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan); Hirai, Y. [Faculty of Science, Ibaraki University, Mito, Ibaraki 310-8512 (Japan); Katagiri, H. [Department of Physical Science, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan)

2009-10-01T23:59:59.000Z

100

Solar gamma rays powered by secluded dark matter  

Science Conference Proceedings (OSTI)

Secluded dark matter models, in which weakly interacting massive particles annihilate first into metastable mediators, can present novel indirect detection signatures in the form of gamma rays and fluxes of charged particles arriving from directions correlated with the centers of large astrophysical bodies within the Solar System, such as the Sun and larger planets. This naturally occurs if the mean free path of the mediator is in excess of the solar (or planetary) radius. We show that existing constraints from water Cerenkov detectors already provide a novel probe of the parameter space of these models, complementary to other sources, with significant scope for future improvement from high angular resolution gamma-ray telescopes such as Fermi-LAT. Fluxes of charged particles produced in mediator decays are also capable of contributing a significant solar system component to the spectrum of energetic electrons and positrons, a possibility which can be tested with the directional and timing information of PAMELA and Fermi.

Batell, Brian; Shang Yanwen [Perimeter Institute for Theoretical Physics, Waterloo, Ontario, N2J 2W9 (Canada); Pospelov, Maxim [Perimeter Institute for Theoretical Physics, Waterloo, Ontario, N2J 2W9 (Canada); Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia, V8P 1A1 (Canada); Ritz, Adam [Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia, V8P 1A1 (Canada)

2010-04-01T23:59:59.000Z

Note: This page contains sample records for the topic "gamma-ray logging systems" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


101

Solar Gamma Rays Powered by Secluded Dark Matter  

E-Print Network (OSTI)

Secluded dark matter models, in which WIMPs annihilate first into metastable mediators, can present novel indirect detection signatures in the form of gamma rays and fluxes of charged particles arriving from directions correlated with the centers of large astrophysical bodies within the solar system, such as the Sun and larger planets. This naturally occurs if the mean free path of the mediator is in excess of the solar (or planetary) radius. We show that existing constraints from water Cerenkov detectors already provide a novel probe of the parameter space of these models, complementary to other sources, with significant scope for future improvement from high angular resolution gamma-ray telescopes such as Fermi-LAT. Fluxes of charged particles produced in mediator decays are also capable of contributing a significant solar system component to the spectrum of energetic electrons and positrons, a possibility which can be tested with the directional and timing information of PAMELA and Fermi.

Brian Batell; Maxim Pospelov; Adam Ritz; Yanwen Shang

2009-10-08T23:59:59.000Z

102

Fermi Observations of Gamma-ray Bursts  

SciTech Connect

The gamma-ray emission mechanism of Gamma-ray bursts (GRBs) are still unknown. Fermi Gamma-ray Space Telescope successfully detected high-energy (> 100 MeV) emission from 17 GRBs since its launch. Fermi revealed the distinct temporal behaviors and extra spectral component from high-energy emission. These new observational results are driving many theoretical implications, such as leptonic, hadronic and afterglow origin. The highest energy photon detected by Fermi gives a constraint on the bulk Lorentz factor of the ultra-relativistic jets of GRBs. The impact of the Fermi GRB observations extends not only to the GRB-related issues but also to the outside GRB physics, such as quantum gravity and model of the extra galactic background light.

Ohno, Masanori [Institute of Space and Astronautical Science, JAXA, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)

2010-10-15T23:59:59.000Z

103

Observations of Gamma Ray Bursts with AGILE  

E-Print Network (OSTI)

The AGILE satellite, in orbit since 2007, localized up to October 2009 about 1 Gamma Ray Burst (GRB) per month with the hard X-ray imager SuperAGILE (18 - 60 keV) (with a rate reduced by a factor 2-3 in spinning mode) and is detecting around 1 GRB per week with the non-imaging Mini-Calorimeter (MCAL, 0.35 - 100 MeV). Up to October 2011 the AGILE Gamma Ray Imaging Detector firmly detected four GRBs in the energy band between 20 MeV and few GeV. In this paper we review the status of the GRBs observation with AGILE and discuss the upper limits in the gamma-ray band of the non-detected events.

Longo, F; Del Monte, E; Marisaldi, M; Fuschino, F; Giuliani, A

2011-01-01T23:59:59.000Z

104

Development of Compton gamma-ray sources at LLNL  

SciTech Connect

Compact Compton scattering gamma-ray sources offer the potential of studying nuclear photonics with new tools. The optimization of such sources depends on the final application, but generally requires maximizing the spectral density (photons/eV) of the gamma-ray beam while simultaneously reducing the overall bandwidth on target to minimize noise. We have developed an advanced design for one such system, comprising the RF drive, photoinjector, accelerator, and electron-generating and electron-scattering laser systems. This system uses a 120 Hz, 250 pC, 2 ps, 0.35 mm mrad electron beam with 250 MeV maximum energy in an X-band accelerator scattering off a 150 mJ, 10 ps, 532 nm laser to generate 5 Multiplication-Sign 10{sup 10} photons/eV/s/Sr at 0.5 MeV with an overall bandwidth of less than 1%. The source will be able to produce photons up to energies of 2.5 MeV. We also discuss Compton scattering gamma-ray source predictions given by numerical codes.

Albert, F.; Anderson, S. G.; Ebbers, C. A.; Gibson, D. J.; Hartemann, F. V.; Marsh, R. A.; Messerly, M. J.; Prantil, M. A.; Wu, S.; Barty, C. P. J. [Lawrence Livermore National Laboratory, NIF and Photon Science, 7000 East avenue, Livermore, CA 94550 (United States)

2012-12-21T23:59:59.000Z

105

Gamma-Ray Bursts: Jets and Energetics  

E-Print Network (OSTI)

The relativistic outflows from gamma-ray bursts are now thought to be narrowly collimated into jets. After correcting for this jet geometry there is a remarkable constancy of both the energy radiated by the burst and the kinetic energy carried by the outflow. Gamma-ray bursts are still the most luminous explosions in the Universe, but they release energies that are comparable to supernovae. The diversity of cosmic explosions appears to be governed by the fraction of energy that is coupled to ultra-relativistic ejecta.

D. A. Frail

2003-11-12T23:59:59.000Z

106

VHE Gamma-ray Supernova Remnants  

SciTech Connect

Increasing observational evidence gathered especially in X-rays and {gamma}-rays during the course of the last few years support the notion that Supernova remnants (SNRs) are Galactic particle accelerators up to energies close to the ''knee'' in the energy spectrum of Cosmic rays. This review summarizes the current status of {gamma}-ray observations of SNRs. Shell-type as well as plerionic type SNRs are addressed and prospect for observations of these two source classes with the upcoming GLAST satellite in the energy regime above 100 MeV are given.

Funk, Stefan; /KIPAC, Menlo Park

2007-01-22T23:59:59.000Z

107

A Shotgun Model for Gamma Ray Bursts  

E-Print Network (OSTI)

We propose that gamma ray bursts (GRBs) are produced by a shower of heavy blobs running into circumstellar material at highly relativistic speeds. The gamma ray emission is produced in the shocks these bullets drive into the surrounding medium. The short term variability seen in GRBs is set by the slowing-down time of the bullets while the overall duration of the burst is set by the lifetime of the central engine. A requirement of this model is that the ambient medium be dense, consistent with a strong stellar wind. The efficiency of the burst can be relatively high.

S. Heinz; M. C. Begelman

1999-08-03T23:59:59.000Z

108

Redshift indicators for gamma-ray bursts  

E-Print Network (OSTI)

The measure of the distances and luminosities of gamma-ray bursts (GRBs) led to the discovery that many GRB properties are strongly correlated with their intrinsic luminosity, leading to the construction of reliable luminosity indicators. These GRB luminosity indicators have quickly found applications, like the construction of 'pseudo-redshifts', or the measure of luminosity distances, which can be computed independently of the measure of the redshift. In this contribution I discuss various issues connected with the construction of luminosity-redshift indicators for gamma-ray bursts.

J-L. Atteia

2005-05-04T23:59:59.000Z

109

A supersymmetric model of gamma ray bursts  

E-Print Network (OSTI)

We propose a model for gamma ray bursts in which a star subject to a high level of fermion degeneracy undergoes a phase transition to a supersymmetric state. The burst is initiated by the transition of fermion pairs to sfermion pairs which, uninhibited by the Pauli exclusion principle, can drop to the ground state of minimum momentum through photon emission. The jet structure is attributed to the Bose statistics of sfermions whereby subsequent sfermion pairs are preferentially emitted into the same state (sfermion amplification by stimulated emission). Bremsstrahlung gamma rays tend to preserve the directional information of the sfermion momenta and are themselves enhanced by stimulated emission.

L. Clavelli; G. Karatheodoris

2004-03-22T23:59:59.000Z

110

Status of the Milagro $\\gamma$ Ray Observatory  

E-Print Network (OSTI)

The Milagro Gamma Ray Observatory is the world's first large-area water Cherenkov detector capable of continuously monitoring the sky at TeV energies. Located in northern New Mexico, Milagro will perform an all sky survey of the Northern Hemisphere at energies between ~250 GeV and 50 TeV. With a high duty cycle, large detector area (~5000 square meters), and a wide field-of-view (~1 sr), Milagro is uniquely capable of searching for transient and DC sources of high-energy gamma-ray emission. Milagro has been operating since February, 1999. The current status of the Milagro Observatory and initial results will be discussed.

Atkins, R; Berley, D; Chen, M L; Coyne, D G; Delay, R S; Dingus, B L; Dorfan, D E; Ellsworth, R W; Evans, D; Falcone, A D; Fleysher, L; Fleysher, R; Gisler, G; Goodman, J A; Haines, T J; Hoffman, C M; Hugenberger, S; Kelley, L A; Leonor, I; Macri, J R; McConnell, M; McCullough, J F; McEnery, J E; Miller, R S; Mincer, A I; Morales, M F; Némethy, P; Ryan, J M; Schneider, M; Shen, B; Shoup, A L; Sinnis, G; Smith, A J; Sullivan, G W; Thompson, T N; Tümer, T O; Wang, K; Wascko, M O; Westerhoff, S; Williams, D A; Yang, T; Yodh, G B

2001-01-01T23:59:59.000Z

111

Ultrahigh Energy Cosmic Rays and Prompt TeV Gamma Rays from Gamma Ray Bursts  

E-Print Network (OSTI)

Gamma Ray Bursts (GRBs) have been proposed as one {\\it possible} class of sources of the Ultrahigh Energy Cosmic Ray (UHECR) events observed up to energies $\\gsim10^{20}\\ev$. The synchrotron radiation of the highest energy protons accelerated within the GRB source should produce gamma rays up to TeV energies. Here we briefly discuss the implications on the energetics of the GRB from the point of view of the detectability of the prompt TeV gamma rays of proton-synchrotron origin in GRBs in the up-coming ICECUBE muon detector in the south pole.

Pijushpani Bhattacharjee; Nayantara Gupta

2003-05-12T23:59:59.000Z

112

Observation of the Crab Nebula in Soft Gamma Rays with the Nuclear Compton Telescope  

E-Print Network (OSTI)

Gamma-ray bursts . . . . . . . . . . . . . . . . . . . 1.268] G. J. Fishman. The gamma-ray burst capabilities of BATSEOlson. Observations of Gamma- Ray Bursts of Cosmic Origin.

Bandstra, Mark ShenYu

2010-01-01T23:59:59.000Z

113

Gamma-ray bursts: a Centauro's cry?  

E-Print Network (OSTI)

A new candidate for the gamma-ray bursts central engine is proposed: if in some energetic cosmic event a macroscopic amount of bubbles of the disoriented chiral condensate can be formed, then their subsequent decays will produce a relativistic fireball without the baryon loading problem. The neutron star to strange star transition is considered as a candidate example of such cosmic event.

Z. K. Silagadze

2003-03-04T23:59:59.000Z

114

Delayed Nickel Decay in Gamma Ray Bursts  

E-Print Network (OSTI)

Recently observed emission lines in the X-ray afterglow of gamma ray bursts suggest that iron group elements are either produced in the gamma ray burst, or are present nearby. If this material is the product of a thermonuclear burn, then such material would be expected to be rich in Nickel-56. If the nickel remains partially ionized, this prevents the electron capture reaction normally associated with the decay of Nickel-56, dramatically increasing the decay timescale. Here we examine the consequences of rapid ejection of a fraction of a solar mass of iron group material from the center of a collapsar/hypernova. The exact rate of decay then depends on the details of the ionization and therefore the ejection process. Future observations of iron, nickel and cobalt lines can be used to diagnose the origin of these elements and to better understand the astrophysical site of gamma ray bursts. In this model, the X-ray lines of these iron-group elements could be detected in suspected hypernovae that did not produce an observable gamma ray burst due to beaming.

G. C. McLaughlin; R. A. M. J. Wijers

2002-05-19T23:59:59.000Z

115

Bremsstrahlung gamma rays from light Dark Matter  

E-Print Network (OSTI)

We discuss the often-neglected role of bremsstrahlung processes on the interstellar gas in computing indirect signatures of Dark Matter (DM) annihilation in the Galaxy, particularly for light DM candidates in the phenomenologically interesting O(10) GeV mass range. Especially from directions close to the Galactic Plane, the expected gamma-ray spectrum is altered via two effects: directly, by the photons emitted in the bremsstrahlung process on the interstellar gas by energetic electrons which are among the DM annihilation byproducts; indirectly, by the modification of the same electron spectrum, due to the additional energy loss process in the diffusion-loss equation (e.g. the resulting inverse Compton emission is altered). We quantify the importance of the bremsstrahlung emission in the GeV energy range, showing that it is the dominant component of the gamma-ray spectrum for some cases. We also find that, in regions in which bremsstrahlung dominates energy losses, the related gamma-ray emission is only moderately sensitive to possible large variations in the gas density. Still, we stress that, for computing precise spectra in the (sub-)GeV range, it is important to obtain a reliable description of the inner Galaxy gas distribution as well as to compute self-consistently the gamma emission and the solution to the diffusion-loss equation. For example, these are crucial issues to quantify and interpret meaningfully gamma-ray map `residuals' in terms of (light) DM annihilations.

Marco Cirelli; Pasquale D. Serpico; Gabrijela Zaharijas

2013-07-26T23:59:59.000Z

116

Galactic Models of Gamma-Ray Bursts  

E-Print Network (OSTI)

We describe observational evidence and theoretical calculations which support the high velocity neutron star model of gamma-ray bursts. We estimate the energetic requirements in this model, and discuss possible energy sources. we also consider radiative processes involved in the bursts.

Donald Q. Lamb; Tomasz Bulik; Paolo S. Coppi

1995-08-20T23:59:59.000Z

117

Neutrino Balls and Gamma-Ray Bursts  

E-Print Network (OSTI)

We propose a mechanism by which the neutrino emission from a supernova-type explosion can be converted into a gamma-ray burst of total energy $\\sim 10^{50}$ ergs. This occurs naturally if the explosion is situated inside a ball of trapped neutrinos, which in turn may lie at a galactic core. There are possible unique signatures of this scenario.

B. Holdom; R. A. Malaney

1993-06-17T23:59:59.000Z

118

A supersymmetric origin of gamma ray bursts  

E-Print Network (OSTI)

Bright bursts of gamma rays from outer space have been puzzling Astronomers for more than thirty years and there is still no conceptually complete model for the phenomenon within the standard model of particle physics. Is it time to consider a supersymmetric (SUSY) origin for these bursts to add to the astronomical indications of supersymmetry from dark matter?

L. Clavelli

2004-10-01T23:59:59.000Z

119

Blazar Duty-Cycle at gamma-ray Frequecies: Constraints from Extragalactic Background Radiation and Prospects for AGILE and GLAST  

E-Print Network (OSTI)

We take into account the constraints from the observed extragalactic gamma-ray background to estimate the maximum duty cycle allowed for a selected sample of WMAP Blazars, in order to be detectable by AGILE and GLAST gamma-ray experiments. For the nominal sensitivity values of both instruments, we identify a subset of sources which can in principle be detectable also in a steady state without over-predicting the extragalactic background. This work is based on the results of a recently derived Blazar radio LogN-LogS obtained by combining several multi-frequency surveys.

Pittori, Carlotta; Colafrancesco, Sergio; Giommi, Paolo

2007-01-01T23:59:59.000Z

120

Gamma-Ray Bursts, Ultra High Energy Cosmic Rays, and Cosmic Gamma-Ray Background  

E-Print Network (OSTI)

We argue that gamma-ray bursts (GRBs) may be the origin of the cosmic gamma-ray background radiation observed in GeV range. It has theoretically been discussed that protons may carry a much larger amount of energy than electrons in GRBs, and this large energy can be radiated in TeV range by synchrotron radiation of ultra-high-energy protons (\\sim 10^{20} eV). The possible detection of GRBs above 10 TeV suggested by the Tibet and HEGRA groups also supports this idea. If this is the case, most of TeV gamma-rays from GRBs are absorbed in intergalactic fields and eventually form GeV gamma-ray background, whose flux is in good agreement with the recent observation.

Tomonori Totani

1998-10-14T23:59:59.000Z

Note: This page contains sample records for the topic "gamma-ray logging systems" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


121

The Starburst Contribution to the Extra-Galactic Gamma-Ray Background  

E-Print Network (OSTI)

Cosmic ray protons interacting with gas at the mean density of the interstellar medium in starburst galaxies lose energy rapidly via inelastic collisions with ambient nuclei. The resulting pions produce secondary electrons and positrons, high-energy neutrinos, and gamma-ray photons. We estimate the cumulative gamma-ray emission from starburst galaxies. We find a total integrated background above 100 MeV of F_gamma ~ 10^{-6} GeV/cm^2/s/sr and a corresponding specific intensity at GeV energies of nuI_nu ~ 10^{-7} GeV/cm^2/s/sr. Starbursts may thus account for a significant fraction of the extra-galactic $\\gamma$-ray background. We show that the FIR-radio correlation provides a strong constraint on the gamma-ray emission from starburst galaxies because pions decay into both gamma-rays and radio-emitting electron/positron pairs. We identify several nearby systems where the potential for observing gamma-ray emission is the most favorable (M82, NGC 253, and IC 342), predict their fluxes, and predict a linear FIR-gamma-ray correlation for the densest starbursts. If established, the FIR-gamma-ray correlation would provide strong evidence for the ``calorimeter'' theory of the FIR-radio correlation and would imply that cosmic rays in starburst galaxies interact with gas at approximately the mean density of the interstellar medium (ISM), thereby providing an important constraint on the physics of the ISM in starbursts.

Todd A. Thompson; Eliot Quataert; Eli Waxman

2006-06-27T23:59:59.000Z

122

CANGAROO-III SEARCH FOR TeV GAMMA RAYS FROM TWO CLUSTERS OF GALAXIES  

SciTech Connect

Because accretion and merger shocks in clusters of galaxies may accelerate particles to high energies, clusters are candidate sites for the origin of ultra-high-energy (UHE) cosmic rays. A prediction was presented for gamma-ray emission from a cluster of galaxies at a detectable level with the current generation of imaging atmospheric Cherenkov telescopes. The gamma-ray emission was produced via inverse Compton upscattering of cosmic microwave background photons by electron-positron pairs generated by collisions of UHE cosmic rays in the cluster. We observed two clusters of galaxies, Abell 3667 and Abell 4038, searching for very high energy gamma-ray emission with the CANGAROO-III atmospheric Cherenkov telescope system in 2006. The analysis showed no significant excess around these clusters, yielding upper limits on the gamma-ray emission. From a comparison of the upper limit for the northwest radio relic region of Abell 3667 with a model prediction, we derive a lower limit for the magnetic field of the region of approx0.1 muG. This shows the potential of gamma-ray observations in studies of the cluster environment. We also discuss the flux upper limit from cluster center regions using a model of gamma-ray emission from neutral pions produced in hadronic collisions of cosmic-ray protons with the intracluster medium. The derived upper limit of the cosmic-ray energy density within this framework is an order of magnitude higher than that of our Galaxy.

Kiuchi, R.; Mori, M.; Enomoto, R.; Kifune, T. [Institute for Cosmic Ray Research, University of Tokyo, Kashiwa, Chiba 277-8582 (Japan); Bicknell, G. V. [Research School of Astronomy and Astrophysics, Australian National University, ACT 2611 (Australia); Clay, R. W. [School of Chemistry and Physics, University of Adelaide, SA 5005 (Australia); Edwards, P. G. [CSIRO Australia Telescope National Facility, Narrabri, NSW 2390 (Australia); Gunji, S.; Inoue, K. [Department of Physics, Yamagata University, Yamagata City, Yamagata 990-8560 (Japan); Hara, S.; Itoh, C. [Ibaraki Prefectural University of Health Sciences, Ami, Ibaraki 300-0394 (Japan); Hara, T. [Faculty of Management Information, Yamanashi Gakuin University, Kofu, Yamanashi 400-8575 (Japan); Hattori, T.; Kawachi, A. [Department of Physics, Tokai University, Hiratsuka, Kanagawa 259-1292 (Japan); Hayashi, S.; Kajino, F. [Department of Physics, Konan University, Kobe, Hyogo 658-8501 (Japan); Higashi, Y.; Kabuki, S. [Department of Physics, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan); Hirai, Y. [Faculty of Science, Ibaraki University, Mito, Ibaraki 310-8512 (Japan); Katagiri, H. [Department of Physical Science, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan)

2009-10-10T23:59:59.000Z

123

BL Lacertae Objects and the Extragalactic Gamma-Ray Background  

E-Print Network (OSTI)

A tight correlation between gamma-ray and radio emission is found for a sample of BL Lacertae (BL Lac) objects detected by Fermi Gamma-ray Space Telescope (Fermi) and the Energetic Gamma-Ray Experiment Telescope (EGRET). The gamma-ray emission of BL Lac objects exhibits strong variability, and the detection rate of gamma-ray BL Lac objects is low, which may be related to the gamma-ray duty cycle of BL Lac objects. We estimate the gamma-ray duty cycle ~ 0.11, for BL Lac objects detected by EGRET and Fermi. Using the empirical relation of gamma-ray emission with radio emission and the estimated gamma-ray duty cycle, we derive the gamma-ray luminosity function (LF) of BL Lac objects from their radio LF. Our derived gamma-ray LF of BL Lac objects can almost reproduce that calculated with the recently released Fermi bright active galactic nuclei (AGN) sample. We find that about 45% of the extragalactic diffuse gamma-ray background (EGRB) is contributed by BL Lac objects. Combining the estimate of the quasar contri...

Li, Fan

2011-01-01T23:59:59.000Z

124

The Biggest Bangs The Mystery of Gamma-Ray Bursts,  

E-Print Network (OSTI)

wide field of view and high duty cycle Milagro is uniquely capable of searching for gamma-ray bursts of gamma-ray bursts have come from observa- tions of afterglows over a wide spectral range. This has allowed detailed modeling of gamma-ray burst afterglow properties both as a function of time

Katz, Jonathan I.

125

The Biggest Bangs The Mystery of Gamma-Ray Bursts,  

E-Print Network (OSTI)

Physique www.sciencedirect.com Gamma-ray burst studies in the SVOM era / �tude des sursauts gamma à l s t r a c t Article history: Available online 13 April 2011 Keywords: Gamma-rays, bursts Stars Black by Elsevier Masson SAS. All rights reserved. 1. Introduction The field of gamma-ray bursts (GRBs) has rapidly

Katz, Jonathan I.

126

Gamma-Ray Bursts Nuclear Test Ban Treaty, 1963  

E-Print Network (OSTI)

Lecture 18 Gamma-Ray Bursts #12;Nuclear Test Ban Treaty, 1963 First Vela satellite pair launched and their predecessors, Vela 4, discovered the first gamma-ray bursts. The discovery was announced by Klebesadel, Strong, and Olson (ApJ, 182, 85) in 1973. #12;First Gamma-Ray Burst The Vela 5 satellites functioned from July, 1969

Harrison, Thomas

127

Characterizing Application Runtime Behavior from System Logs and Metrics  

Science Conference Proceedings (OSTI)

Large-scale systems are heavily shared resource environments where a mix of applications are launched concurrently competing for network and storage resources. It is essential to characterize the runtime behavior of these applications for provisioning system resources and understanding the impact of application s performance when competing for resources. In this paper, we study the use of zero- and low-overhead system logs and other system metric data for characterizing the runtime behavior of several applications. We present our preliminary work on estimating individual application s I/O demands by observing file system usage pattern over multiple runs, and interpreting application s network utilization characteristics by observing link-layer error logs. We also present preliminary findings on using such information in making context-sensitive scheduling decisions that minimize potentially negative interactions between applications competing for shared resources. Our analysis is based on four months of system log data collected on one of the world s largest supercomputing facilities, the Jaguar XT5 petaflop system at Oak Ridge National Laboratory.

Gunasekaran, Raghul [ORNL; Dillow, David A [ORNL; Shipman, Galen M [ORNL; Vuduc, Richard [Georgia Institute of Technology; Chow, Edmond [Georgia Institute of Technology

2011-01-01T23:59:59.000Z

128

The Universe Viewed in Gamma-Rays 1 Toward Ultra Short Gamma Ray Burst Ground Based De-  

E-Print Network (OSTI)

-TIME FERMI LARGE AREA TELESCOPE GAMMA-RAY BURST AFTERGLOWS C. A. Swenson1 , A. Maxham2 , P. W. A. Roming1 2010 June 11; published 2010 June 28 ABSTRACT GRB 090926A was detected by both the Gamma-ray Burst the predicted gamma-ray fluence, as would have been seen by the Burst Alert Telescope (BAT) on board Swift

Enomoto, Ryoji

129

SGARFACE: A Novel Detector For Microsecond Gamma Ray Bursts  

E-Print Network (OSTI)

The Short GAmma Ray Front Air Cherenkov Experiment (SGARFACE) is operated at the Whipple Observatory utilizing the Whipple 10m gamma-ray telescope. SGARFACE is sensitive to gamma-ray bursts of more than 100MeV with durations from 100ns to 35us and provides a fluence sensitivity as low as 0.8 gamma-rays per m^2 above 200MeV (0.05 gamma-rays per m^2 above 2GeV) and allows to record the burst time structure.

S. LeBohec; F. Krennrich; G. Sleege

2005-01-11T23:59:59.000Z

130

Neutron-driven gamma-ray laser  

DOE Patents (OSTI)

A lasing cylinder emits laser radiation at a gamma-ray wavelength of 0.87 {angstrom} when subjected to an intense neutron flux of about 400 eV neutrons. A 250 {angstrom} thick layer of Be is provided between two layers of 100 {angstrom} thick layer of {sup 57}Co and these layers are supported on a foil substrate. The coated foil is coiled to form the lasing cylinder. Under the neutron flux {sup 57}Co becomes {sup 58}Co by neutron absorption. The {sup 58}Co then decays to {sup 57}Fe by 1.6 MeV proton emission. {sup 57}Fe then transitions by mesne decay to a population inversion for lasing action at 14.4 keV. Recoil from the proton emission separates the {sup 57}Fe from the {sup 57}Co and into the Be, where Mossbauer emission occurs at a gamma-ray wavelength.

Bowman, C.D.

1989-03-28T23:59:59.000Z

131

Neutron-driven gamma-ray laser  

DOE Patents (OSTI)

A lasing cylinder emits laser radiation at a gamma-ray wavelength of 0.87 .ANG. when subjected to an intense neutron flux of about 400 eV neutrons. A 250 .ANG. thick layer of Be is provided between two layers of 100 .ANG. thick layer of .sup.57 Co and these layers are supported on a foil substrate. The coated foil is coiled to form the lasing cylinder. Under the neutron flux .sup.57 Co becomes .sup.58 Co by neutron absorption. The .sup.58 Co then decays to .sup.57 Fe by 1.6 MeV proton emission. .sup.57 Fe then transitions by mesne decay to a population inversion for lasing action at 14.4 keV. Recoil from the proton emission separates the .sup.57 Fe from the .sup.57 Co and into the Be, where Mossbauer emission occurs at a gamma-ray wavelength.

Bowman, Charles D. (Los Alamos, NM)

1990-01-01T23:59:59.000Z

132

Virtual Gamma Ray Radiation Sources through Neutron Radiative Capture  

SciTech Connect

The countrate response of a gamma spectrometry system from a neutron radiation source behind a plane of moderating material doped with a nuclide of a large radiative neutron capture cross-section exhibits a countrate response analogous to a gamma radiation source at the same position from the detector. Using a planar, surface area of the neutron moderating material exposed to the neutron radiation produces a larger area under the prompt gamma ray peak in the detector than a smaller area of dimensions relative to the active volume of the gamma detection system.

Scott Wilde, Raymond Keegan

2008-07-01T23:59:59.000Z

133

Lecture 7Lecture 7 The GammaThe Gamma--RayRay  

E-Print Network (OSTI)

Milagro­A TeV Observatory for Gamma Ray Bursts B.L. Dingus and the Milagro Collaboration Los energy gamma-rays from gamma-ray bursts. The highest energy gamma rays supply very strong constraints on the nature of gamma-ray burst sources as well as fundamental physics. Because the highest energy gamma-rays

134

A Link between Prompt Optical and Prompt Gamma-Ray Emission in Gamma-Ray Bursts  

E-Print Network (OSTI)

The prompt optical emission that arrives with gamma-rays from a cosmic gamma-ray burst (GRB) is a signature of the engine powering the burst, the properties of the ultra-relativistic ejecta of the explosion, and the ejecta's interactions with the surroundings. Until now, only GRB 990123 had been detected at optical wavelengths during the burst phase. Its prompt optical emission was variable and uncorrelated with the prompt gamma-ray emission, suggesting that the optical emission was generated by a reverse shock arising from the ejecta's collision with the surrounding material. Here we report prompt optical emission from GRB 041219a. It is variable and correlated with the prompt gamma-rays, indicating a common origin for the optical light and the gamma-rays. Within the context of the standard fireball model of GRBs, we attribute this new optical component to internal shocks driven into the burst ejecta by variations of the inner engine. The correlated optical emission is a direct probe of the jet isolated from the medium. The timing of the uncorrelated optical emission is strongly dependent on the nature of the medium.

W. T. Vestrand; P. R. Wozniak; J. A. Wren; E. E. Fenimore; T. Sakamoto; R. R. White; D. Casperson; H. Davis; S. Evans; M. Galassi; K. E. McGowan; J. A. Schier; J. W. Asa; S. D. Barthelmy; J. R. Cummings; N. Gehrels; D. Hullinger; H. A. Krimm; C. B. Markwardt; K. McLean; D. Palmer; A. Parsons; J. Tueller

2005-03-23T23:59:59.000Z

135

Gamma-rays from PSR B1259 -63  

E-Print Network (OSTI)

The high-energy gamma-ray emission discovered using the H.E.S.S. telescopes from the binary system PSR B1259 -63, is modelled using an extension of the approach that successfully predicted it. We find that the simultaneous INTEGRAL and H.E.S.S. data permit both a model with dominant radiative losses, high pulsar wind Lorentz factor and modest efficiency as well as one with dominant adiabatic losses, a slower wind and higher efficiency. Additional, simultaneous, X-ray and TeV data sets are needed to lift this degeneracy.

J. G. Kirk; Lewis Ball; S. Johnston

2005-09-30T23:59:59.000Z

136

Gravitational radiation from long gamma-ray bursts  

E-Print Network (OSTI)

Long gamma-ray bursts (GRBs) are probably powered by high-angular momentum black hole-torus systems in suspended accretion. The torus will radiate gravitational waves as non-axisymmetric instabilities develop. The luminosity in gravitational-wave emissions is expected to compare favorably with the observed isotropic equivalent luminosity in GRB-afterglow emissions. This predicts that long GRBs are potentially the most powerful LIGO/VIRGO burst-sources in the Universe. Their frequency-dynamics is characterized by a horizontal branch in the $\\dot{f}(f)-$diagram.

Maurice H. P. M. van Putten

2001-02-11T23:59:59.000Z

137

GAMMA RAYS FROM STAR FORMATION IN CLUSTERS OF GALAXIES  

SciTech Connect

Star formation in galaxies is observed to be associated with gamma-ray emission, presumably from non-thermal processes connected to the acceleration of cosmic-ray nuclei and electrons. The detection of gamma rays from starburst galaxies by the Fermi Large Area Telescope (LAT) has allowed the determination of a functional relationship between star formation rate and gamma-ray luminosity. Since star formation is known to scale with total infrared (8-1000 {mu}m) and radio (1.4 GHz) luminosity, the observed infrared and radio emission from a star-forming galaxy can be used to quantitatively infer the galaxy's gamma-ray luminosity. Similarly, star-forming galaxies within galaxy clusters allow us to derive lower limits on the gamma-ray emission from clusters, which have not yet been conclusively detected in gamma rays. In this study, we apply the functional relationships between gamma-ray luminosity and radio and IR luminosities of galaxies derived by the Fermi Collaboration to a sample of the best candidate galaxy clusters for detection in gamma rays in order to place lower limits on the gamma-ray emission associated with star formation in galaxy clusters. We find that several clusters have predicted gamma-ray emission from star formation that are within an order of magnitude of the upper limits derived in Ackermann et al. based on non-detection by Fermi-LAT. Given the current gamma-ray limits, star formation likely plays a significant role in the gamma-ray emission in some clusters, especially those with cool cores. We predict that both Fermi-LAT over the course of its lifetime and the future Cerenkov Telescope Array will be able to detect gamma-ray emission from star-forming galaxies in clusters.

Storm, Emma M.; Jeltema, Tesla E.; Profumo, Stefano [Department of Physics, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)

2012-08-20T23:59:59.000Z

138

Development of geothermal logging systems in the United States  

DOE Green Energy (OSTI)

Logging technologies developed for hydrocarbon resource evaluation have not migrated into geothermal applications even though data so obtained would strengthen reservoir characterization efforts. Two causative issues have impeded progress: (1) there is a general lack of vetted, high-temperature instrumentation, and (2) the interpretation of log data generated in a geothermal formation is in its infancy. Memory-logging tools provide a path around the first obstacle by providing quality data at a low cost. These tools feature on-board computers that process and store data, and newer systems may be programmed to make decisions. Since memory tools are completely self-contained, they are readily deployed using the slick line found on most drilling locations. They have proven to be rugged, and a minimum training program is required for operator personnel. Present tools measure properties such as temperature and pressure, and the development of noise, deviation, and fluid conductivity logs based on existing hardware is relatively easy. A more complex geochemical tool aimed at a quantitative analysis of (potassium, uranium and thorium) is in the calibration phase, and it is expandable into all nuclear measurements common in the hydrocarbon industry. A fluid sampling tool is in the design phase. All tools are designed for operation at conditions exceeding 400 C, and for deployment in the slim holes produced by mining-coring operations. Partnerships are being formed between the geothermal industry and scientific drilling programs to define and develop inversion algorithms relating raw tool data to more pertinent information. These cooperative efforts depend upon quality guidelines such as those under development within the international Ocean Drilling Program.

Lysne, P.

1994-04-01T23:59:59.000Z

139

Neutrino Event Rates from Gamma Ray Bursts  

E-Print Network (OSTI)

We recalculate the diffuse flux of high energy neutrinos produced by Gamma Ray Bursts (GRB) in the relativistic fireball model. Although we confirm that the average single burst produces only ~10^{-2} high energy neutrino events in a detector with 1 km^2 effective area, i.e. about 10 events per year, we show that the observed rate is dominated by burst-to-burst fluctuations which are very large. We find event rates that are expected to be larger by one order of magnitude, likely more, which are dominated by a few very bright bursts. This greatly simplifies their detection.

F. Halzen; D. W. Hooper

1999-08-12T23:59:59.000Z

140

Can Naked Singularities Yield Gamma Ray Bursts?  

E-Print Network (OSTI)

Gamma-ray bursts are believed to be the most luminous objects in the Universe. There has been some suggestion that these arise from quantum processes around naked singularities. The main problem with this suggestion is that all known examples of naked singularities are massless and hence there is effectively no source of energy. It is argued that a globally naked singularity coupled with quantum processes operating within a distance of the order of Planck length of the singularity will probably yield energy burst of the order of M_pc^2\\approx2\\times 10^{16} ergs, where M_p is the Planck mass.

H. M. Antia

1998-07-09T23:59:59.000Z

Note: This page contains sample records for the topic "gamma-ray logging systems" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


141

Gamma Ray Burst Neutrinos Probing Quantum Gravity  

E-Print Network (OSTI)

Very high energy, short wavelength, neutrinos may interact with the space-time foam predicted by theories of quantum gravity. They would propagate like light through a crystal lattice and be delayed, with the delay depending on the energy. This will appear to the observer as a violation of Lorenz invariance. Back of the envelope calculations imply that observations of neutrinos produced by gamma ray bursts may reach Planck-scale sensitivity. We revisit the problem considering two essential complications: the imprecise timing of the neutrinos associated with their poorly understood production mechanism in the source and the indirect nature of their energy measurement made by high energy neutrino telescopes.

M. C. Gonzalez-Garcia; F. Halzen

2006-11-28T23:59:59.000Z

142

High-energy gamma rays in Hiroshima and Nagasaki: Implications for risk and W{sub R}  

SciTech Connect

Based on the DS86 dosimetry system, nearly all of the dose to survivors of the atomic bombings of Hiroshima and Nagasaki was due to unusually high-energy gamma rays, predominantly in the 2- to 5-MeV range. These high energies resulted in part from neutron capture gamma rays as the bomb neutrons penetrated large distances of air. Because of the inverse relationship between energy and biological effectiveness, these high-energy gamma rays are expected to be substantially less effective in producing biological damage than the radiations commonly used in radiobiology and risk assessment. This observation has implications for radiation protection and risk assessment.

Straume, T. [Lawrence Livermore National Lab., CA (United States)

1995-12-01T23:59:59.000Z

143

Bremsstrahlung {gamma}-ray generation by electrons from gas jets irradiated by laser pulses for radiographic testing  

Science Conference Proceedings (OSTI)

Electron generation from a gas jet irradiated by low energy femtosecond laser pulses is studied experimentally as a promising source of radiation for radioisotope-free {gamma}-ray imaging systems. The calculated yield of {gamma}-rays in the 0.5-2 MeV range, produced by low-average-power lasers and gas targets, exceeds the yields from solid tape targets up to 60 times. In addition, an effect of quasi-mono energetic electrons on {gamma}-ray imaging is also discussed.

Oishi, Yuji; Nayuki, Takuya; Zhidkov, Alexei; Fujii, Takashi; Nemoto, Koshichi [Central Research Institute of Electric Power Industry, Yokosuka, Kanagawa 240-0196 (Japan); Central Research Institute of Electric Power Industry, Yokosuka, Kanagawa 240-0196, Japan and Photon Pioneers Center in Osaka University, Yamadaoka 2-1, Suita, Osaka 565-0871 (Japan); Central Research Institute of Electric Power Industry, Yokosuka, Kanagawa 240-0196 (Japan)

2012-07-11T23:59:59.000Z

144

GAMQUEST, a Computer Program to Identify Gamma Rays  

NLE Websites -- All DOE Office Websites (Extended Search)

GAMQUEST GAMQUEST A Computer Program to Identify Gamma Rays Edgardo Browne, Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 EBROWNE@LBL.Gov Table of Contents Introduction. Program Access and Output Files. How to Run GAMQUEST. From Individual Accounts. From Guest Account. Gamma-Ray Data. GAMQUEST, a Tool for Applied Research. Searching Strategies. Examples. Neutron Activation Analysis. Gamma-Ray Spectrum Between 100 and 800 keV. Gamma-Ray Spectrum Between 800 and 1600 keV. A List of X Rays and Gamma Rays from the Decay of 192Ir (74 hr). Run GAMQUEST from Guest Account Acknowledgments. References. 1. Introduction. The characteristic energies and intensities of gamma rays emitted by radioactive isotopes are commonly used as fingerprints for isotope

145

Gamma-ray burst interaction with dense interstellar medium  

E-Print Network (OSTI)

Interaction of cosmological gamma ray burst radiation with the dense interstellar medium of host galaxy is considered. Gas dynamical motion of interstellar medium driven by gamma ray burst is investigated in 2D approximation for different initial density distributions of host galaxy matter and different total energy of gamma ray burst. The maximum velocity of motion of interstellar medium is $1.8\\cdot10^4$ km/s. Light curves of gamma ray burst afterglow are calculated for set of non homogeneous density, distribution gamma ray burst total energy, and different viewing angles. Spectra of gamma ray burst afterglow are modeled taking into account conversion of hard photons (soft X-ray, hard UV) to soft UV and optics photons.

Maxim Barkov; Gennady Bisnovatyi-Kogan

2004-10-07T23:59:59.000Z

146

X-Ray Observations of Gamma-Ray Burst Afterglows  

E-Print Network (OSTI)

The discovery by the BeppoSAX satellite of X-ray afterglow emission from the gamma-ray burst which occurred on 28 February 1997 produced a revolution in our knowledge of the gamma-ray burst phenomenon. Along with the discovery of X-ray afterglows, the optical afterglows of gamma-ray bursts were discovered and the distance issue was settled, at least for long $\\gamma$-ray bursts. The 30 year mystery of the gamma-ray burst phenomenon is now on the way to solution. Here I rewiew the observational status of the X-ray afterglow emission, its mean properties (detection rate, continuum spectra, line features, and light curves), and the X-ray constraints on theoretical models of gamma-ray bursters and their progenitors. I also discuss the early onset afterglow emission, the remaining questions, and the role of future X-ray afterglow observations.

Filippo Frontera

2004-06-25T23:59:59.000Z

147

Gamma-Ray Bursts Observed with the Spectrometer SPI Onboard INTEGRAL  

E-Print Network (OSTI)

The spectrometer SPI is one of the main detectors of ESA's INTEGRAL mission. The instrument offers two interesting and valuable capabilities for the detection of the prompt emission of Gamma-ray bursts. Within a field of view of 16 degrees, SPI is able to localize Gamma-ray bursts with an accuracy of 10 arcmin. The large anticoincidence shield, ACS, consisting of 512 kg of BGO crystals, detects Gamma-ray bursts quasi omnidirectionally above ~70 keV. Burst alerts from SPI/ACS are distributed to the interested community via the INTEGRAL Burst Alert System. The ACS data have been implemented into the 3rd Interplanetary Network and have proven valuable for the localization of bursts using the triangulation method. During the first 8 months of the mission approximately one Gamma-ray burst per month was localized within the field of fiew of SPI and 145 Gamma-ray burst candidates were detected by the ACS from which 40 % have been confirmed by other instruments.

A. von Kienlin; A. Rau; V. Beckmann; S. Deluit

2004-07-07T23:59:59.000Z

148

The Use of Gamma-Ray Imaging to Improve Portal Monitor Performance  

SciTech Connect

We have constructed a prototype, rapid-deployment portal monitor that uses visible-light and gamma-ray imaging to allow simultaneous monitoring of multiple lanes of traffic from the side of a roadway. Our Roadside Tracker uses automated target acquisition and tracking (TAT) software to identify and track vehicles in visible light images. The field of view of the visible camera overlaps with and is calibrated to that of a one-dimensional gamma-ray imager. The TAT code passes information on when vehicles enter and exit the system field of view and when they cross gamma-ray pixel boundaries. Based on this in-formation, the gamma-ray imager "harvests" the gamma-ray data specific to each vehicle, integrating its radiation signature for the entire time that it is in the field of view. In this fashion we are able to generate vehicle-specific radiation signatures and avoid source confusion problems that plague nonimaging approaches to the same problem.

Ziock, Klaus-Peter [ORNL; Collins, Jeff [Lawrence Livermore National Laboratory (LLNL); Fabris, Lorenzo [ORNL; Gee, Timothy Felix [ORNL; Goddard, James K [ORNL; Habte Ghebretatios, Frezghi [ORNL; Karnowski, Thomas Paul [ORNL

2008-01-01T23:59:59.000Z

149

The Animated Gamma-ray Sky Revealed by the Fermi Gamma-ray Space Telescope  

SciTech Connect

The Fermi Gamma-ray Space Telescope has been observing the sky in gamma-rays since August 2008. In addition to breakthrough capabilities in energy coverage (20 MeV-300 GeV) and angular resolution, the wide field of view of the Large Area Telescope enables observations of 20% of the sky at any instant, and of the whole sky every three hours. It has revealed a very animated sky with bright gamma-ray bursts flashing and vanishing in minutes, powerful active galactic nuclei flaring over hours and days, many pulsars twinkling in the Milky Way, and X-ray binaries shimmering along their orbit. Most of these variable sources had not been seen by the Fermi predecessor, EGRET, and the wealth of new data already brings important clues to the origin of the high-energy emission and particles powered by the compact objects. The telescope also brings crisp images of the bright gamma-ray emission produced by cosmic-ray interactions in the interstellar medium, thus allowing to measure the cosmic nuclei and electron spectra across the Galaxy, to weigh interstellar clouds, in particular in the dark-gas phase. The telescope sensitivity at high energy will soon provide useful constraints on dark-matter annihilations in a variety of environments. I will review the current results and future prospects of the Fermi mission.

Grenier, Isabelle (University Paris Diderot and CEA Saclay, France)

2009-04-01T23:59:59.000Z

150

The Multiwavelength Approach to Unidentified Gamma-Ray Sources  

E-Print Network (OSTI)

As the highest-energy photons, gamma rays have an inherent interest to astrophysicists and particle physicists studying high-energy, nonthermal processes. Gamma-ray telescopes complement those at other wavelengths, especially radio, optical, and X-ray, providing the broad, mutiwavelength coverage that has become such a powerful aspect of modern astrophysics. Multiwavelength techniques of various types have been developed to help identify and explore unidentified gamma-ray sources. This overview summarizes the ideas behind several of these methods.

David J. Thompson

2004-07-20T23:59:59.000Z

151

Gamma Ray Bursts, Neutron Star Quakes, and the Casimir Effect  

E-Print Network (OSTI)

We propose that the dynamic Casimir effect is a mechanism that converts the energy of neutron starquakes into $\\gamma$--rays. This mechanism efficiently produces photons from electromagnetic Casimir energy released by the rapid motion of a dielectric medium into a vacuum. Estimates based on the cutoff energy of the gamma ray bursts and the volume involved in a starquake indicate that the total gamma ray energy emission is consonant with observational requirements.

C. Carlson; T. Goldman; J. Perez-Mercader

1994-11-25T23:59:59.000Z

152

Nuclear Criticality as a Contributor to Gamma Ray Burst Events  

E-Print Network (OSTI)

Most gamma ray bursts are able to be explained using supernovae related phenomenon. Some measured results still lack compelling explanations and a contributory cause from nuclear criticality is proposed. This is shown to have general properties consistent with various known gamma ray burst properties. The galactic origin of fast rise exponential decay gamma ray bursts is considered a strong candidate for these types of events.

Robert Bruce Hayes

2013-01-15T23:59:59.000Z

153

Monte Carlo Simulations of Neutron Oil well Logging Tools  

E-Print Network (OSTI)

Monte Carlo simulations of simple neutron oil well logging tools into typical geological formations are presented.The simulated tools consist of both 14 MeV pulsed and continuous Am-Be neutron sources with time gated and continuous gamma ray detectors respectively.The geological formation consists of pure limestone with 15% absolute porosity in a wide range of oil saturation.The particle transport was performed with the Monte Carlo N-Particle Transport Code System, MCNP-4B.Several gamma ray spectra were obtained at the detector position that allow to perform composition analysis of the formation.In particular, the ratio C/O was analyzed as an indicator of oil saturation.Further calculations are proposed to simulate actual detector responses in order to contribute to understand the relation between the detector response with the formation composition

Azcurra, M

2002-01-01T23:59:59.000Z

154

Inelastic cross sections from gamma-ray measurements  

Science Conference Proceedings (OSTI)

Measurements of gamma rays following neutron induced reactions have been studied with the Germanium Array for Neutron-induced Excitations (GEANIE) at the Los Alamos Neutron Science Center (LANSCE) for many years. Gamma-ray excitation functions and coincidence studies provide insight into nuclear reaction mechanisms as well as expanding our knowledge of energy levels and gamma-rays. Samples studied with Ge detectors at LANSCE range from Be to Pu. Fe, Cr and Ti have been considered for use as reference cross sections. An overview of the measurements and efforts to create a reliable neutron-induced gamma-ray reference cross section will be presented.

Nelson, Ronald Owen [Los Alamos National Laboratory

2010-12-06T23:59:59.000Z

155

Future Facilities for Gamma-Ray Pulsar Studies  

E-Print Network (OSTI)

Pulsars seen at gamma-ray energies offer insight into particle acceleration to very high energies, along with information about the geometry and interaction processes in the magnetospheres of these rotating neutron stars. During the next decade, a number of new gamma-ray facilities will become available for pulsar studies. This brief review describes the motivation for gamma-ray pulsar studies, the opportunities for such studies, and some specific discussion of the capabilities of the Gamma-ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT) for pulsar measurements.

D. J. Thompson

2003-10-17T23:59:59.000Z

156

The Diverse Environments of Gamma-Ray Bursts.  

E-Print Network (OSTI)

??I present results from several years of concerted observations of the afterglows and host galaxies of gamma-ray bursts (GRBs), the most energetic explosions in the… (more)

Perley, Daniel Alan

2011-01-01T23:59:59.000Z

157

X-ray Flares in Gamma-Ray Bursts.  

E-Print Network (OSTI)

??Data from the Swift mission have now shown that flares are a common component of Gamma-Ray Burst afterglows, appearing in roughly 50% of GRBs to… (more)

Morris, David

2008-01-01T23:59:59.000Z

158

Astrophysical and Astrobiological effects of Gamma-Ray Bursts.  

E-Print Network (OSTI)

??O presente trabalho tem o objetivo principal de compreender os possíveis efeitos da radiação energética de um evento de Gamma-Ray Burst (GRB) sobre o meio… (more)

Douglas Galante

2009-01-01T23:59:59.000Z

159

Supermassive Objects as Gamma-Ray Bursters  

E-Print Network (OSTI)

We propose that the gravitational collapse of supermassive objects ($ M\\ga 10^4 M_\\odot$), either as relativistic star clusters or as single supermassive stars (which may result from stellar mergers in dense star clusters), could be a cosmological source of $\\gamma$-ray bursts. These events could provide the seeds of the supermassive black holes observed at the center of many galaxies. Collapsing supermassive objects will release a fraction of their huge gravitational binding energy as thermal neutrino pairs. We show that the accompanying neutrino/antineutrino annihilation-induced heating could drive electron/positron ``fireball'' formation, relativistic expansion, and associated $\\gamma$-ray emission. The major advantage of this model is its energetics: supermassive object collapses are far more energetic than solar mass-scale compact object mergers; therefore, the conversion of gravitational energy to fireball kinetic energy in the supermassive object scenario need not be highly efficient, nor is it necessary to invoke directional beaming. The major weakness of this model is difficulty in avoiding a baryon loading problem for one dimensional collapse scenarios.

George M. Fuller; Xiangdong Shi

1997-11-04T23:59:59.000Z

160

Two Classes of Gamma-Ray Bursts  

E-Print Network (OSTI)

If gamma-ray bursts are at cosmological distances, as suggested by their isotropy on the sky and the comparative deficiency of weak bursts, then they represent radiated energies of ? 1051 erg, and imply the release of an even greater energy. Only neutron stars and black holes have binding energies sufficient to power such extraordinarily violent and energetic events. General considerations of neutrino opacity imply1 that the escape of a neutron star’s (or black hole’s) binding energy requires a time of about 10 sec, as shown by the observed duration of neutrino emission from SN1987A. The distribution of durations of gamma-ray bursts is known2 to be bimodal, with one peak between 10 and 100 sec and the other between 0.1 and 1 sec. We hypothesize that the durations of the longer bursts may be explained as the result of the diffusion of energy, by means of neutrinos, from a forming neutron star or black hole, but that the brevity of the shorter bursts requires different physics. An alternative hypothesis supposes that all bursts (excepting soft gamma repeaters, which we do not discuss) represent a single class of events, whose differing durations reflect differences in one or more parameters. These two hypotheses may be tested using data from the recently released 3B Catalogue3.

J. I. Katz; L. M. Canel

1995-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "gamma-ray logging systems" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


161

A Theory of Gamma-Ray Bursts  

E-Print Network (OSTI)

We present a specific scenario for the link between GRB and hypernovae, based on Blandford-Znajek extraction of black-hole spin energy. Such a mechanism requires a high angular momentum in the progenitor object. The observed association of gamma-ray bursts with type Ibc supernovae leads us to consider massive helium stars that form black holes at the end of their lives as progenitors. We combine the numerical work of MacFadyen & Woosley with analytic calculations, to show that about 1E53 erg each are available to drive the fast GRB ejecta and the supernova. The GRB ejecta are driven by the power output through the open field lines, whereas the supernova is powered by closed filed lines and jet shocks. We also present a much simplified approximate derivation of these energetics. Helium stars that leave massive black-hole remnants in special ways, namely via soft X-ray transients or very massive WNL stars. Since binaries naturally have high angular momentum, we propose a link between black-hole transients and gamma-ray bursts. Recent observations of one such transient, GRO J1655-40/Nova Scorpii 1994, explicitly support this connection: its high space velocity indicates that substantial mass was ejected in the formation of the black hole, and the overabundance of alpha-nuclei, especially sulphur, indicates that the explosion energy was extreme, as in SN 1998bw/GRB 980425. (abstract shortened)

G. E. Brown; C. -H. Lee; R. A. M. J. Wijers; H. K. Lee; G. Israelian; H. A. Bethe

2000-03-23T23:59:59.000Z

162

Chukwa: a system for reliable large-scale log collection  

Science Conference Proceedings (OSTI)

Large Internet services companies like Google, Yahoo, and Facebook use the MapReduce programming model to process log data. MapReduce is designed to work on data stored in a distributed filesystem like Hadoop's HDFS. As a result, a number of log collection ... Keywords: logging, research, scale

Ariel Rabkin; Randy Katz

2010-11-01T23:59:59.000Z

163

Binary Pulsar Shock Emissions as Galactic Gamma-Ray Sources  

E-Print Network (OSTI)

We address several issues regarding the interpretation of galactic \\ggg-ray sources. We consider powerful pulsars in binaries producing X-ray and gamma-ray {\\it unpulsed} emission from the shock interaction of relativistic pulsar winds with circumbinary material. Nebular mass outflows from companion stars of binary pulsars can provide the right {\\it calorimeters} to transform a fraction of the electromagnetic and kinetic energy of pulsar winds into high energy radiation. We discuss the physics of interaction of relativistic pulsar winds with gaseous material and show that the conditions in pulsar binary systems might be ideal to constrain shock acceleration mechanisms and pulsar wind composition and structure. We briefly discuss the example of the 47~ms pulsar PSR~1259-63 orbiting around a massive Be~star companion and monitored by X-ray and gamma-ray instruments during its recent periastron passage. In addition to young pulsars in massive binaries, also a class of recycled millisecond pulsars in low-mass binaries can be interesting high energy emitters.

M. Tavani

1995-02-10T23:59:59.000Z

164

Binary pulsar shock emissions as galactic gamma-ray sources  

E-Print Network (OSTI)

We address several issues regarding the interpretation of galactic \\ggg-ray sources. We consider powerful pulsars in binaries producing X-ray and gamma-ray {\\it unpulsed} emission from the shock interaction of relativistic pulsar winds with circumbinary material. Nebular mass outflows from companion stars of binary pulsars can provide the right {\\it calorimeters} to transform a fraction of the electromagnetic and kinetic energy of pulsar winds into high energy radiation. We discuss the physics of interaction of relativistic pulsar winds with gaseous material and show that the conditions in pulsar binary systems might be ideal to constrain shock acceleration mechanisms and pulsar wind composition and structure. We briefly discuss the example of the 47~ms pulsar PSR~1259-63 orbiting around a massive Be~star companion and monitored by X-ray and gamma-ray instruments during its recent periastron passage. In addition to young pulsars in massive binaries, also a class of recycled millisecond pulsars in low-mass bin...

Tavani, M

1995-01-01T23:59:59.000Z

165

No Evidence for Gamma-Ray Burst/Abell Cluster or Gamma- Ray Burst/Radio-Quiet Quasar Correlations  

E-Print Network (OSTI)

We examine the recent claims that cosmic gamma-ray bursts are associated with either radio-quiet quasars or Abell clusters. These associations were based on positional coincidences between cataloged quasars or Abell clusters, and selected events from the BATSE 3B catalog of gamma-ray bursts. We use a larger sample of gamma-ray bursts with more accurate positions, obtained by the 3rd Interplanetary Network, to re-evaluate these possible associations. We find no evidence for either.

K. Hurley; D. H. Hartmann; C. Kouveliotou; R. M. Kippen; J. Laros; T. Cline; M. Boer

1998-11-28T23:59:59.000Z

166

Variable Very High Energy Gamma-ray Emission from the Microquasar LS I +61 303  

E-Print Network (OSTI)

Microquasars are binary star systems with relativistic radio-emitting jets. They are potential sources of cosmic rays and laboratories for elucidating the physics of relativistic jets. Here we report the detection of variable gamma-ray emission above 100 gigaelectron volts from the microquasar LS I +61 303. Six orbital cycles were recorded. Several detections occur at a similar orbital phase, suggesting the emission is periodic. The strongest gamma-ray emission is not observed when the two stars are closest to one another, implying a strong orbital modulation of the emission or the absorption processes.

MAGIC Collaboration; J. Albert

2006-05-22T23:59:59.000Z

167

THE NEW CANGAROO TELESCOPE AND THE PROSPECT OF VHE GAMMA RAY OBSERVATION AT  

E-Print Network (OSTI)

), the doppler boosting of secondary gamma-rays is sufficient to produce TeV gamma-rays. Gamma-ray bursts: Fireballs expanding with relativistic speed explain gamma-ray bursts at cosmological distancesStudy of Celestial Objects with Very High Energy Gamma Rays CANGAROO III Project Description

Enomoto, Ryoji

168

Compton scattering effects on the duration of terrestrial gamma-ray flashes  

E-Print Network (OSTI)

; published 18 January 2012. [1] Terrestrial gamma-ray flashes (TGFs) are gamma-ray bursts detected from space) recently discovered by the gamma-ray burst monitor (GBM) aboard the Fermi Gamma-Ray Space Telescope. Introduction [2] Terrestrial gamma-ray flashes (TGFs) are bursts of high-energy photons originating from

Pasko, Victor

169

Study of Celestial Objects with Very High Energy Gamma Rays CANGAROO III  

E-Print Network (OSTI)

), the doppler boosting of secondary gamma-rays is sufficient to produce TeV gamma-rays. Gamma-ray bursts: Fireballs expanding with relativistic speed explain gamma-ray bursts at cosmological distancesStudy of Celestial Objects with Very High Energy Gamma Rays CANGAROO III Project Description

Enomoto, Ryoji

170

OBSERVATIONS OF THE PROMPT GAMMA-RAY EMISSION OF GRB 070125 Eric C. Bellm,1  

E-Print Network (OSTI)

2007 November 13; accepted 2008 July 25 ABSTRACT The long, bright gamma-ray burst GRB 070125: gamma rays: bursts 1. INTRODUCTION The prompt gamma-ray emission of gamma-ray bursts (GRBs) is the mostOBSERVATIONS OF THE PROMPT GAMMA-RAY EMISSION OF GRB 070125 Eric C. Bellm,1 Kevin Hurley,1 Valentin

California at Berkeley, University of

171

X-RAYRICH GAMMA-RAY BURSTS, PHOTOSPHERES, AND VARIABILITY P. Meszaros,1,2  

E-Print Network (OSTI)

X-RAY­RICH GAMMA-RAY BURSTS, PHOTOSPHERES, AND VARIABILITY P. Me´sza´ros,1,2 E. Ramirez-Ruiz,3 M. J of the observational gamma-ray variability-luminosity relation. Subject headings: gamma rays: bursts -- radiation mechanisms: nonthermal 1. INTRODUCTION Gamma-ray burst (GRB) light curves at gamma-ray ener- gies are often

Zhang, Bing

172

Variability of EGRET Gamma-Ray Sources  

E-Print Network (OSTI)

The variability of the high-energy gamma ray sources in the Third EGRET catalog is analyzed by a new method. We re-analyze the EGRET data to calculate a likelihood function for the flux of each source in each observation, both for detections and upper limits. These functions can be combined in a uniform manner with a simple model of the flux distribution to characterize the flux variation by a confidence interval for the relative standard deviation of the flux. The main result is a table of these values for almost all the cataloged sources. As expected, the identified pulsars are steady emitters and the blazars are mostly highly variable. The unidentified sources are heterogeneous, with greater variation at higher Galactic latitude. There is an indication that pulsar wind nebulae are associated with variable sources. There is a population of variable sources along the Galactic plane, concentrated in the inner spiral arms.

P. L. Nolan; W. F. Tompkins; I. A. Grenier; P. F. Michelson

2003-07-10T23:59:59.000Z

173

Short Gamma-Ray Bursts Are Different  

E-Print Network (OSTI)

We analyze BATSE time-tagged event (TTE) data for short gamma-ray bursts (T90 duration burst. Performing the cross-correlation between two energy bands, we measure an average lag ~ 20-40 x shorter than for long bursts, and a lag distribution close to symmetric about zero - unlike long bursts. Using a "Bayesian Block" method to identify significantly distinct pulse peaks, we find an order of magnitude fewer pulses than found in studies of long bursts. The disparity in lag magnitude is discontinuous across the ~ 2-s valley between long and short bursts. Thus, short bursts do not appear to be representable as a continuation of long bursts' temporal characteristics.

J. P. Norris; J. D. Scargle; J. T. Bonnell

2001-05-07T23:59:59.000Z

174

Millisecond Proto-Magnetars & Gamma Ray Bursts  

E-Print Network (OSTI)

In the seconds after core collapse and explosion, a thermal neutrino-driven wind emerges from the cooling, deleptonizing newly-born neutron star. If the neutron star has a large-scale magnetar-strength surface magnetic field and millisecond rotation period, then the wind is driven primarily by magneto-centrifugal slinging, and only secondarily by neutrino interactions. The strong magnetic field forces the wind to corotate with the stellar surface and the neutron star's rotational energy is efficiently extracted. As the neutron star cools, and the wind becomes increasingly magnetically-dominated, the outflow becomes relativistic. Here I review the millisecond magnetar model for long-duration gamma ray bursts and explore some of the basic physics of neutrino-magnetocentrifugal winds. I further speculate on some issues of collimation and geometry in the millisecond magnetar model.

Todd A. Thompson

2005-04-27T23:59:59.000Z

175

Perspectives on Gamma-Ray Pulsar Emission  

SciTech Connect

Pulsars are powerful sources of radiation across the electromagnetic spectrum. This paper highlights some theoretical insights into non-thermal, magnetospheric pulsar gamma-ray radiation. These advances have been driven by NASA's Fermi mission, launched in mid-2008. The Large Area Telescope (LAT) instrument on Fermi has afforded the discrimination between polar cap and slot gap/outer gap acceleration zones in young and middle-aged pulsars. Altitude discernment using the highest energy pulsar photons will be addressed, as will spectroscopic interpretation of the primary radiation mechanism in the LAT band, connecting to both polar cap/slot gap and outer gap scenarios. Focuses will mostly be on curvature radiation and magnetic pair creation, including population trends that may afford probes of the magnetospheric accelerating potential.

Baring, Matthew G. [Department of Physics and Astronomy, MS-108, Rice University, P. O. Box 1892, Houston, TX 77251-1892 (United States)

2011-09-21T23:59:59.000Z

176

Constraining Lorentz violations with Gamma Ray Bursts  

E-Print Network (OSTI)

Gamma ray bursts are excellent candidates to constrain physical models which break Lorentz symmetry. We consider deformed dispersion relations which break the boost invariance and lead to an energy-dependent speed of light. In these models, simultaneously emitted photons from cosmological sources reach Earth with a spectral time delay that depends on the symmetry breaking scale. We estimate the possible bounds which can be obtained by comparing the spectral time delays with the time resolution of available telescopes. We discuss the best strategy to reach the strongest bounds. We compute the probability of detecting bursts that improve the current bounds. The results are encouraging. Depending on the model, it is possible to build a detector that within several years will improve the present limits of 0.015 m_pl.

Maria Rodriguez Martinez; Tsvi Piran

2006-01-10T23:59:59.000Z

177

COMPTEL Observations of Gamma-ray Bursts  

E-Print Network (OSTI)

INTRODUCTION The origin of cosmic g-ray bursts is as mysterious today as it was when they were discovered more than 25 years ago. Despite a wealth of new observational data obtained with the BATSE instrument on board the Compton Gamma Ray Observatory, many of the fundamental questions remain unanswered. For instance, although BATSE has provided a tremendous statistical advantage (allowing the most accurate measurement of the spatial isotropy and inhomogeneity of burst sources ), its limited angular resolution and spectral range have given us an incomplete picture of the small-scale angular source distribution and high energy emission properties. 2,3 Furthermore, the limited angular resolution has also made it difficult to search for burst counterparts at other wavelengths. The COMPTEL instrument on board Compton measures the locations and spectra (0.75-30 MeV) of several strong g-ray bursts per year which occur within the ~1 sr fieldof -view of the main ("telescope") instrument.

Kippen Ryan Connors; R. M. Kippen; B J. Ryan; B A. Connors; B M. Mcconnell; V. Schönfelder; C J. Greiner; C M. Varendorff; W. Collmar; C W. Hermsen; D L. Kuiper; D C. Winkler; L. O. Hanlon E; K. S. O’flaherty E

1995-01-01T23:59:59.000Z

178

Establishing a connection between high-power pulsars and very-high-energy gamma-ray sources  

E-Print Network (OSTI)

In the very-high-energy (VHE) gamma-ray wave band, pulsar wind nebulae (PWNe) represent to date the most populous class of Galactic sources. Nevertheless, the details of the energy conversion mechanisms in the vicinity of pulsars are not well understood, nor is it known which pulsars are able to drive PWNe and emit high-energy radiation. In this paper we present a systematic study of a connection between pulsars and VHE gamma-ray sources based on a deep survey of the inner Galactic plane conducted with the High Energy Stereoscopic System (H.E.S.S.). We find clear evidence that pulsars with large spin-down energy flux are associated with VHE gamma-ray sources. This implies that these pulsars emit on the order of 1% of their spin-down energy as TeV gamma-rays.

Carrigan, S; Hofmann, W; Kosack, K; Lohse, T; Reimer, O

2007-01-01T23:59:59.000Z

179

Gravitational Waves versus Electromagnetic Emission in Gamma-Ray Bursts  

E-Print Network (OSTI)

The recent progress in the understanding the physical nature of neutron star equilibrium configurations and the first observational evidence of a genuinely Short Gamma-Ray Burst, GRB 090227B, allows to give an estimate of the gravitational waves versus electromagnetic emission in a Gamma-Ray Burst.

Jorge A. Rueda; Remo Ruffini

2012-05-31T23:59:59.000Z

180

A simple empirical redshift indicator for gamma-ray bursts  

E-Print Network (OSTI)

We propose a new empirical redshift indicator for gamma-ray bursts. This indicator is easily computed from the gamma-ray burst spectral parameters, and its duration, and it provides ``pseudo-redshifts'' accurate to a factor two. Possible applications of this redshift indicator are briefly discussed.

J-L Atteia

2003-04-17T23:59:59.000Z

Note: This page contains sample records for the topic "gamma-ray logging systems" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


181

LONG GAMMA-RAY TRANSIENTS FROM COLLAPSARS  

Science Conference Proceedings (OSTI)

In the collapsar model for common gamma-ray bursts (GRBs), the formation of a centrifugally supported disk occurs during the first {approx}10 s following the collapse of the iron core in a massive star. This only occurs in a small fraction of massive stellar deaths, however, and requires unusual conditions. A much more frequent occurrence could be the death of a star that makes a black hole and a weak or absent outgoing shock, but in a progenitor that only has enough angular momentum in its outermost layers to make a disk. We consider several cases where this is likely to occur-blue supergiants with low mass-loss rates, tidally interacting binaries involving either helium stars or giant stars, and the collapse to a black hole of very massive pair-instability supernovae. These events have in common the accretion of a solar mass or so of material through a disk over a period much longer than the duration of a common GRB. A broad range of powers is possible, 10{sup 47}-10{sup 50} erg s{sup -1}, and this brightness could be enhanced by beaming. Such events were probably more frequent in the early universe where mass-loss rates were lower. Indeed, this could be one of the most common forms of gamma-ray transients in the universe and could be used to study first generation stars. Several events could be active in the sky at any one time. Recent examples of this sort of event may have been the Swift transients Sw-1644+57, Sw-2058+0516, and GRB 101225A.

Woosley, S. E. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Heger, Alexander, E-mail: woosley@ucolick.org, E-mail: alex@physics.umn.edu [Minnesota Institute of Astrophysics, School of Physics and Astronomy, University of Minnesota, Twin Cities, Minneapolis, MN 55455 (United States)

2012-06-10T23:59:59.000Z

182

Magnetic Structures in Gamma-Ray Burst Jets Probed by Gamma-Ray Polarization  

E-Print Network (OSTI)

We report polarization measurements in two prompt emissions of gamma-ray bursts, GRB 110301A and GRB 110721A, observed with the Gamma-ray burst polarimeter (GAP) aboard IKAROS solar sail mission. We detected linear polarization signals from each burst with polarization degree of $\\Pi = 70 \\pm 22$% with statistical significance of $3.7 \\sigma$ for GRB 110301A, and $\\Pi = 84^{+16}_{-28}$% with $3.3 \\sigma$ confidence level for GRB 110721A. We did not detect any significant change of polarization angle. These two events had shorter durations and dimmer brightness compared with GRB 100826A, which showed a significant change of polarization angle, as reported in Yonetoku et al. (2011). Synchrotron emission model can be consistent with all the data of the three GRBs, while photospheric quasi-thermal emission model is not favorable. We suggest that magnetic field structures in the emission region are globally-ordered fields advected from the central engine.

Daisuke Yonetoku; Toshio Murakami; Shuichi Gunji; Tatehiro Mihara; Kenji Toma; Yoshiyuki Morihara; Takuya Takahashi; Yudai Wakashima; Hajime Yonemochi; Tomonori Sakashita; Noriyuki Toukairin; Hirofumi Fujimoto; Yoshiki Kodama

2012-08-27T23:59:59.000Z

183

MAGNETIC STRUCTURES IN GAMMA-RAY BURST JETS PROBED BY GAMMA-RAY POLARIZATION  

SciTech Connect

We report polarization measurements in two prompt emissions of gamma-ray bursts, GRB 110301A and GRB 110721A, observed with the gamma-ray burst polarimeter (GAP) on borad the IKAROS solar sail mission. We detected linear polarization signals from each burst with polarization degree of {Pi} = 70 {+-} 22% with statistical significance of 3.7{sigma} for GRB 110301A, and {Pi} = 84{sup +16}{sub -28}% with 3.3{sigma} confidence level for GRB 110721A. We did not detect any significant change of polarization angle. These two events had shorter durations and dimmer brightness compared with GRB 100826A, which showed a significant change of polarization angle, as reported in Yonetoku et al. Synchrotron emission model can be consistent with the data of the three GRBs, while the photospheric quasi-thermal emission model is not favored. We suggest that magnetic field structures in the emission region are globally ordered fields advected from the central engine.

Yonetoku, Daisuke; Murakami, Toshio; Morihara, Yoshiyuki; Takahashi, Takuya; Wakashima, Yudai; Yonemochi, Hajime; Sakashita, Tomonori; Fujimoto, Hirofumi; Kodama, Yoshiki [College of Science and Engineering, School of Mathematics and Physics, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192 (Japan); Gunji, Shuichi; Toukairin, Noriyuki [Department of Physics, Faculty of Science, Yamagata University, 1-4-12, Koshirakawa, Yamagata, Yamagata 990-8560 (Japan); Mihara, Tatehiro [Cosmic Radiation Laboratory, RIKEN, 2-1, Hirosawa, Wako City, Saitama 351-0198 (Japan); Toma, Kenji, E-mail: yonetoku@astro.s.kanazawa-u.ac.jp [Department of Earth and Space Science, Osaka University, Toyonaka 560-0043 (Japan)

2012-10-10T23:59:59.000Z

184

The Quest for Gamma Rays:The Quest for Gamma Rays: Exploring the Most Violent PlacesExploring the Most Violent Places  

E-Print Network (OSTI)

beyond our Galaxy. Keywords: very high energy gamma rays, pulsar, active galactic nuclei, gamma ray burst as well as about `after glow' of southern gamma ray bursts which BeppoSAX satellite detected with aboutTHE NEW CANGAROO TELESCOPE AND THE PROSPECT OF VHE GAMMA RAY OBSERVATION AT WOOMERA TADASHI KIFUNE

185

THE BRIGHT GAMMA-RAY BURST OF 2000 FEBRUARY 10: A CASE STUDY OF AN OPTICALLY DARK GAMMA-RAY BURST  

E-Print Network (OSTI)

THE BRIGHT GAMMA-RAY BURST OF 2000 FEBRUARY 10: A CASE STUDY OF AN OPTICALLY DARK GAMMA-RAY BURST L Received 2002 January 16; accepted 2002 June 8 ABSTRACT The gamma-ray burst GRB 000210 had the highest: observations -- gamma-rays: bursts 1. INTRODUCTION It is observationally well established that about half

Fynbo, Johan

186

Polarization mesurements of gamma ray bursts and axion like particles  

E-Print Network (OSTI)

A polarized gamma ray emission spread over a sufficiently wide energy band from a strongly magnetized astrophysical object like gamma ray bursts (GRBs) offers an opportunity to test the hypothesis of axion like particles (ALPs). Based on evidences of polarized gamma ray emission detected in several gamma ray bursts we estimated the level of ALPs induced dichroism, which could take place in the magnetized fireball environment of a GRB. This allows to estimate the sensitivity of polarization measurements of GRBs to the ALP-photon coupling. This sensitivity $\\gag\\le 2.2\\cdot 10^{-11} {\\rm GeV^{-1}}$ calculated for the ALP mass $m_a=10^{-3}~{\\rm eV}$ and MeV energy spread of gamma ray emission is competitive with the sensitivity of CAST and becomes even stronger for lower ALPs masses.

Andre Rubbia; Alexander Sakharov

2008-09-03T23:59:59.000Z

187

Prompt Optical Observations of Gamma-Ray Bursts  

E-Print Network (OSTI)

The Robotic Optical Transient Search Experiment (ROTSE) seeks to measure simultaneous and early afterglow optical emission from gamma-ray bursts (GRBs). A search for optical counterparts to six GRBs with localization errors of 1 square degree or better produced no detections. The earliest limiting sensitivity is mROTSE> 13.1 at 10.85 seconds (5 second exposure) after the gamma-ray rise, and the best limit is mROTSE> 16.0 at 62 minutes (897 second exposure). These are the most stringent limits obtained for GRB optical counterpart brightness in the first hour after the burst. Consideration of the gamma-ray fluence and peak flux for these bursts and for GRB990123 indicates that there is not a strong positive correlation between optical flux and gamma-ray emission. Subject headings: gamma rays: bursts, observations 1.

Carl Akerlof; Richard Balsano; Scott Barthelmy; Jeff Bloch; Paul Butterworth; Tom Cline; Ra Fletcher; Galen Gisler; John Heise; Jack Hills; Kevin Hurley; Robert Kehoe; Brian Lee; Stuart Marshall; Tim Mckay; Andrew Pawl; Luigi Piro; John Szymanski; Jim Wren

2000-01-01T23:59:59.000Z

188

High Energy Gamma-Ray Emission from Gamma-Ray Bursts - Before GLAST  

Science Conference Proceedings (OSTI)

Gamma-ray bursts (GRBs) are short and intense emission of soft {gamma}-rays, which have fascinated astronomers and astrophysicists since their unexpected discovery in 1960s. The X-ray/optical/radio afterglow observations confirm the cosmological origin of GRBs, support the fireball model, and imply a long-activity of the central engine. The high-energy {gamma}-ray emission (> 20 MeV) from GRBs is particularly important because they shed some lights on the radiation mechanisms and can help us to constrain the physical processes giving rise to the early afterglows. In this work, we review observational and theoretical studies of the high-energy emission from GRBs. Special attention is given to the expected high-energy emission signatures accompanying the canonical early-time X-ray afterglow that was observed by the Swift X-ray Telescope. We also discuss the detection prospect of the upcoming GLAST satellite and the current ground-based Cerenkov detectors.

Fan, Yi-Zhong; Piran, Tsvi

2011-11-29T23:59:59.000Z

189

Compton Recoil Electron Tracking With the TIGRE Gamma-Ray Balloon Experiment  

E-Print Network (OSTI)

AGNs), pulsars, gamma-ray bursts, cosmic ray interactionssensitive to cosmic gamma-ray bursts in the energy range ofGalactic center, a single gamma-ray burst which occurred 10

Kamiya, Kaoru

2011-01-01T23:59:59.000Z

190

Observations of Gamma-Ray Burst Afterglows with the AEOS Burst Camera.  

E-Print Network (OSTI)

??Gamma-ray bursts (GRBs), are variable bursts of gamma-ray radiation, that lasts from milliseconds to hundreds of seconds. These bursts of gamma rays are detected in… (more)

Flewelling, Heather Anne

2009-01-01T23:59:59.000Z

191

Feasibility of GRB with TeV gamma ray all sky monitor  

E-Print Network (OSTI)

We discuss feasibility of Gamma ray burst (GRB) with TeV gamma ray all sky monitor and discuss necessity of TeV gamma ray cherenkov all sky monitor.

S. Osone

2003-05-14T23:59:59.000Z

192

The Search for Muon Neutrinos from Northern Hemisphere Gamma-Ray Bursts with AMANDA  

E-Print Network (OSTI)

see also the Swift Gamma-Ray Burst Mission Page: http://from Northern Hemisphere Gamma-Ray Bursts with AMANDA A.Northern Hemisphere Gamma-Ray Bursts with AMANDA The IceCube

Achterberg, A.; IceCube Collaboration

2008-01-01T23:59:59.000Z

193

GRB 020410: A Gamma-ray burst afterglow discovered by its supernova light  

E-Print Network (OSTI)

Training Network “Gamma-Ray Bursts: An Enigma and a Tool”,Journal GRB 020410: A Gamma-Ray Burst Afterglow DiscoveredSubject headings: gamma rays: bursts – supernova: general

2004-01-01T23:59:59.000Z

194

Search for muon neutrinos from Gamma-Ray Bursts with the IceCube neutrino telescope  

E-Print Network (OSTI)

2009, GCN: The Gamma ray bursts Coordinates Network, http://for muon neutrinos from Gamma-Ray Bursts with the IceCubeMereghetti, S. 2004, in Gamma-ray Bursts: 30 Years of

Abbasi, R.

2010-01-01T23:59:59.000Z

195

Long gamma-ray bursts and core-collapse supernovae have different environments  

E-Print Network (OSTI)

of two classes of gamma-ray bursts. Astrophys. J. 413, 6.V. et al. Host galaxies of gamma-ray bursts: Spectral energyal. Are the hosts of gamma-ray bursts sub-luminous and blue

2006-01-01T23:59:59.000Z

196

Gamma-ray astronomy: From Fermi up to the HAWC high-energy {gamma}-ray observatory in Sierra Negra  

SciTech Connect

Gamma-rays represent the most energetic electromagnetic window for the study of the Universe. They are studied both from space at MeV and GeV energies, with instruments like the Fermi{gamma}-ray Space Telescope, and at TeV energies with ground based instruments profiting of particle cascades in the atmosphere and of the Cerenkov radiation of charged particles in the air or in water. The Milagro gamma-ray observatory represented the first instrument to successfully implement the water Cerenkov technique for {gamma}-ray astronomy, opening the ground for the more sensitive HAWC {gamma}-ray observatory, currently under development in the Sierra Negra site and already providing early science results.

Carraminana, Alberto [Instituto Nacional de Astrofisica, Optica y Electronica Luis Enrique Erro 1, Tonantzintla, Puebla 72840 (Mexico); Collaboration: HAWC Collaboration

2013-06-12T23:59:59.000Z

197

Waves on Noncommutative Spacetime and Gamma-Ray Bursts  

E-Print Network (OSTI)

Quantum group Fourier transform methods are applied to the study of processes on noncommutative Minkowski spacetime $[x^i,t]=\\imath\\lambda x^i$. A natural wave equation is derived and the associated phenomena of {\\it in vacuo} dispersion are discussed. Assuming the deformation scale $\\lambda$ is of the order of the Planck length one finds that the dispersion effects are large enough to be tested in experimental investigations of astrophysical phenomena such as gamma-ray bursts. We also outline a new approach to the construction of field theories on the noncommutative spacetime, with the noncommutativity equivalent under Fourier transform to non-Abelianness of the `addition law' for momentum in Feynman diagrams. We argue that CPT violation effects of the type testable using the sensitive neutral-kaon system are to be expected in such a theory.

Giovanni Amelino-Camelia; Shahn Majid

1999-07-14T23:59:59.000Z

198

GRAVITATIONAL WAVES OF JET PRECESSION IN GAMMA-RAY BURSTS  

SciTech Connect

The physical nature of gamma-ray bursts (GRBs) is believed to involve an ultra-relativistic jet. The observed complex structure of light curves motivates the idea of jet precession. In this work, we study the gravitational waves of jet precession based on neutrino-dominated accretion disks around black holes, which may account for the central engine of GRBs. In our model, the jet and the inner part of the disk may precess along with the black hole, which is driven by the outer part of the disk. Gravitational waves are therefore expected to be significant from this black-hole-inner-disk precession system. By comparing our numerical results with the sensitivity of some detectors, we find that it is possible for DECIGO and BBO to detect such gravitational waves, particularly for GRBs in the Local Group.

Sun Mouyuan; Liu Tong; Gu Weimin; Lu Jufu, E-mail: tongliu@xmu.edu.cn [Department of Physics and Institute of Theoretical Physics and Astrophysics, Xiamen University, Xiamen, Fujian 361005 (China)

2012-06-10T23:59:59.000Z

199

Compact Gamma-ray Source Technology Development Study  

SciTech Connect

This study focuses on the applicability of current accelerator and laser technologies to the construction of compact, narrow bandwidth, gamma-ray sources for DHS missions in illicit materials detection. It also identifies research and development areas in which advancement will directly benefit these light sources. In particular, we review the physics of Compton scattering based light sources and emphasize the source properties most important to Nuclear Resonance Fluorescence (NRF) applications of interest. The influences of laser and electron beam properties on the light source are examined in order to evaluate the utility of different technologies for this application. Applicable bulk and fiber-based laser systems and laser recirculation technologies are discussed and Radio Frequency (RF) Linear Accelerator (linac) technologies are examined to determine the optimal frequency and pulse formats achievable.

Anderson, S G; Gibson, D J; Rusnak, B

2009-09-25T23:59:59.000Z

200

VERY HIGH ENERGY {gamma}-RAY EMISSION FROM PASSIVE SUPERMASSIVE BLACK HOLES: CONSTRAINTS FOR NGC 1399  

Science Conference Proceedings (OSTI)

Very high energy (VHE, >100 GeV) {gamma}-rays are expected to be emitted from the vicinity of supermassive black holes (SMBHs), irrespective of their activity state. In the magnetosphere of rotating SMBH, efficient acceleration of charged particles can take place through various processes. These particles could reach energies up to E {approx} 10{sup 19} eV. VHE {gamma}-ray emission from these particles is then feasible via leptonic or hadronic processes. Therefore, passive systems, where the lack of a strong photon field allows the VHE {gamma}-rays to escape, are expected to be detected by Cherenkov telescopes. We present results from recent VHE experiments on the passive SMBH in the nearby elliptical galaxy NGC 1399. No {gamma}-ray signal has been found, neither by the H.E.S.S. experiment nor in the Fermi data analyzed here. We discuss possible implications for the physical characteristics of the system. We conclude that in a scenario where particles are accelerated in vacuum gaps in the magnetosphere, only a fraction {approx}0.3 of the gap is available for particle acceleration, indicating that the system is unlikely to be able to accelerate protons up to E {approx} 10{sup 19} eV.

Pedaletti, G.; Wagner, S. J. [Landessternwarte, Universitaet Heidelberg, Koenigstuhl, D-69117 Heidelberg (Germany); Rieger, F. M., E-mail: gpedalet@lsw.uni-heidelberg.de [Max-Planck-Institut fuer Kernphysik, P.O. Box 103980, D-69029 Heidelberg (Germany)

2011-09-10T23:59:59.000Z

Note: This page contains sample records for the topic "gamma-ray logging systems" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


201

Particle Acceleration and Gamma-Ray Production in Shell Remnants  

E-Print Network (OSTI)

A number of nearby Northern Hemisphere shell-type Supernova Remnants (SNRs) has been observed in TeV gamma rays, but none of them could be detected so far. This failure calls for a critical reevaluation of the theoretical arguments for gamma-ray emission of SNRs. The present paper discusses diffusive shock acceleration in shell-type SNRs in full kinetic theory. Emphasis is also given to the possible problems for VHE gamma-ray production due to the environmental conditions a SN progenitor finds itself in. Observational upper limits are compared with theoretical predictions for the gamma-ray flux. Empirical arguments from the observation of X-ray power law continua for electron-induced Inverse Compton gamma-ray emission at TeV energies are discussed in their relation to the nucleonic Pi-zero decay emission from the same objects. Finally, a point is made for the simplest case of SNe Ia, expected to explode in a uniform circumstellar medium. Here in particular the very recently detected Southern Hemisphere remnant of SN 1006 is compared with Tycho's SNR. On the basis of the assumed parameters for the two remnants SN 1006 is tentatively identified with a remnant whose TeV gamma-ray emission is dominated by Inverse Compton radiation. Tycho might be dominantly a Pi-zero decay gamma-ray source.

H. J. Volk

1997-11-18T23:59:59.000Z

202

The Gamma-ray Albedo of the Moon  

E-Print Network (OSTI)

We use the GEANT4 Monte Carlo framework to calculate the gamma-ray albedo of the Moon due to interactions of cosmic ray (CR) nuclei with moon rock. Our calculation of the albedo spectrum agrees with the EGRET data. We show that the spectrum of gamma rays from the Moon is very steep with an effective cutoff around 3-4 GeV (600 MeV for the inner part of the Moon disk) and exhibits a narrow pion-decay line at 67.5 MeV, perhaps unique in astrophysics. Apart from other astrophysical sources, the albedo spectrum of the Moon is well understood, including its absolute normalisation; this makes it a useful "standard candle" for gamma-ray telescopes. The steep albedo spectrum also provides a unique opportunity for energy calibration of gamma-ray telescopes, such as the forthcoming Gamma Ray Large Area Space Telescope (GLAST). Since the albedo flux depends on the incident CR spectrum which changes over the solar cycle, it is possible to monitor the CR spectrum using the albedo gamma-ray flux. Simultaneous measurements of CR proton and helium spectra by the Payload for Antimatter-Matter Exploration and Light-nuclei Astrophysics (PAMELA), and observations of the albedo gamma rays by the GLAST Large Area Telescope (LAT), can be used to test the model predictions and will enable the LAT to monitor the CR spectrum near the Earth beyond the lifetime of the PAMELA.

Igor V. Moskalenko; Troy A. Porter

2007-08-21T23:59:59.000Z

203

1 UNIDENTIFIED GAMMA-RAY SOURCES AND MICROQUASARS  

E-Print Network (OSTI)

Some phenomenological properties of the unidentified EGRET detections suggest that there are two distinct groups of galactic gamma-ray sources that might be associated with compact objects endowed with relativistic jets. We discuss different models for gamma-ray production in both microquasars with low- and high-mass stellar companions. We conclude that the parent population of low-latitude and halo variable sources might be formed by yet undetected microquasars and microblazars. Key words: Gamma ray sources: unidentified; microquasars; black holes. 1.

G. E. Romero; I. A Grenier; M. M. Kaufman Bernadó; I. F. Mirabel; D. F. Torres

2004-01-01T23:59:59.000Z

204

Gamma Ray Burst Constraints on Ultraviolet Lorentz Invariance Violation  

E-Print Network (OSTI)

We present a unified general formalism for ultraviolet Lorentz invariance violation (LV) testing through electromagnetic wave propagation, based on both dispersion and rotation measure data. This allows for a direct comparison of the efficacy of different data to constrain LV. As an example we study the signature of LV on the rotation of the polarization plane of $\\gamma$-rays from gamma ray bursts in a LV model. Here $\\gamma$-ray polarization data can provide a strong constraint on LV, 13 orders of magnitude more restrictive than a potential constraint from the rotation of the cosmic microwave background polarization proposed by Gamboa, L\\'{o}pez-Sarri\\'{o}n, and Polychronakos (2006).

Tina Kahniashvili; Grigol Gogoberidze; Bharat Ratra

2006-07-04T23:59:59.000Z

205

RELATIVISTIC SHOCK BREAKOUTS-A VARIETY OF GAMMA-RAY FLARES: FROM LOW-LUMINOSITY GAMMA-RAY BURSTS TO TYPE Ia SUPERNOVAE  

SciTech Connect

The light from a shock breakout of stellar explosions, which carries a wealth of information, strongly depends on the shock velocity at the time of the breakout. The emission from Newtonian breakouts, typical in regular core-collapse supernovae (SNe), has been explored extensively. However, a large variety of explosions result in mildly or ultrarelativistic breakouts, where the observed signature is unknown. Here we calculate the luminosity and spectrum produced by relativistic breakouts. In order to do so, we improve the analytic description of relativistic radiation-mediated shocks and follow the system from the breakout itself, through the planar phase and into the spherical phase. We limit our calculation to cases where the post-breakout acceleration of the gas ends during the planar phase (i.e., the final gas Lorentz factor {approx}< 30). We find that spherical relativistic breakouts produce a flash of gamma rays with energy, E{sub bo}, temperature, T{sub bo}, and duration, t{sup obs} b{sub o}, that provide the breakout radius ( Almost-Equal-To 5 R{sub Sun }(t{sup obs}{sub bo}/10 s)(T{sub bo}/50 keV){sup 2}) and the Lorentz factor ( Almost-Equal-To T{sub bo}/50 keV). They also always satisfy a relativistic breakout relation (t{sup obs}{sub bo}/20 s) {approx} (E{sub bo}/10{sup 46} erg){sup 1/2}(T{sub bo}/50 keV){sup -2.68}. The breakout flare is typically followed, on longer timescales, by X-rays that carry a comparable energy. We apply our model to a variety of explosions, including Type Ia and .Ia SNe, accretion-induced collapse, energetic SNe, and gamma-ray bursts (GRBs). We find that all these events produce detectable gamma-ray signals, some of which may have already been seen. Some particular examples are: (1) relativistic shock breakouts provide a natural explanation to the energy, temperature, and timescales of low-luminosity GRBs. Indeed, all observed low-luminosity GRBs satisfy the relativistic breakout relation. (2) Nearby broad-line Type Ib/c (like SN 2002ap) may produce a detectable {gamma}-ray signal. (3) Galactic Type Ia SNe may produce detectable {gamma}-ray flares. We conclude that relativistic shock breakouts provide a generic process for the production of gamma-ray flares.

Nakar, Ehud [Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978 (Israel); Sari, Re'em [Racah Institute for Physics, Hebrew University, Jerusalem 91904 (Israel)

2012-03-10T23:59:59.000Z

206

of Bright, Long Gamma-Ray Bursts  

E-Print Network (OSTI)

The time profiles of many gamma-ray bursts observed by BATSE consist of distinct pulses, which offer the possibility of characterizing the temporal structure of these bursts using a relatively small set of pulse-shape parameters. This pulse analysis has previously been performed on some bright, long bursts using binned data, and on some short bursts using BATSE Time-Tagged Event (TTE) data. The BATSE Time-to-Spill (TTS) burst data records the times required to accumulate a fixed number of photons, giving variable time resolution. The spill times recorded in the TTS data behave as a gamma distribution. We have developed an interactive pulse-fitting program using the pulse model of Norris et al. and a maximum-likelihood fitting algorithm to the gamma distribution of the spill times. We then used this program to analyze a number of bright, long bursts for which TTS data is available. We present statistical information on the attributes of pulses comprising these bursts.

Andrew Lee; Elliott Bloom; Jeffrey Scargle

1996-01-01T23:59:59.000Z

207

The gamma-ray burst GB 920622  

E-Print Network (OSTI)

We have analyzed the Ulysses, BATSE, and COMPTEL spectral data from the \\gamma-ray burst of June 22, 1992 (GB 920622). COMPTEL data reveal a hard to soft evolution within the first pulse of the burst, while the mean hardness ratios of the three pulses are the same. Unlike the single instrument spectra, the composite spectrum of GB 920622 averaged over the total burst duration ranging from 20 keV up to 10 MeV cannot be fit by a single power law. Instead, the spectrum shows continuous curvature across the full energy range. COMPTEL imaging and BATSE/Ulysses triangulation constrain the source location of GB 920622 to a ring sector 1.1 arcmin wide and 2 degrees long. This area has been searched for quiescent X-ray sources using \\ros survey data collected about two years before the burst. After the optical identification of the X-ray sources in and near the GRB location we conclude that no quiescent X-ray counterpart candidate for GB 920622 has been found.

Greiner, J; Bade, N; Fishman, G J; Hanlon, L O; Hurley, K; Kippen, R M; Kouveliotou, C; Preece, R D; Ryan, J; Schönfelder, V; Williams, O R; Winkler, C M; Boër, M; Niel, M

1995-01-01T23:59:59.000Z

208

A Theory of Gamma-Ray Bursts  

E-Print Network (OSTI)

We present a specific scenario for the link between GRB and hypernovae, based on Blandford-Znajek extraction of black-hole spin energy. Such a mechanism requires a high angular momentum in the progenitor object. The observed association of gamma-ray bursts with type Ibc supernovae leads us to consider massive helium stars that form black holes at the end of their lives as progenitors. We combine the numerical work of MacFadyen & Woosley with analytic calculations, to show that about 1E53 erg each are available to drive the fast GRB ejecta and the supernova. The GRB ejecta are driven by the power output through the open field lines, whereas the supernova is powered by closed filed lines and jet shocks. We also present a much simplified approximate derivation of these energetics. Helium stars that leave massive black-hole remnants in special ways, namely via soft X-ray transients or very massive WNL stars. Since binaries naturally have high angular momentum, we propose a link between black-hole transients a...

Brown, G E; Wijers, R A M J; Lee, H K; Israelian, G; Bethe, Hans Albrecht

2000-01-01T23:59:59.000Z

209

A Search for Gamma-Ray Bursts and Pulsars, and the Application of Kalman Filters to Gamma-Ray Reconstruction  

E-Print Network (OSTI)

Part I describes the analysis of periodic and transient signals in EGRET data. A method to search for the transient flux from gamma-ray bursts independent of triggers from other gamma-ray instruments is developed. Several known gamma-ray bursts were independently detected, and there is evidence for a previously unknown gamma-ray burst candidate. Statistical methods using maximum likelihood and Bayesian inference are developed and implemented to extract periodic signals from gamma-ray sources in the presence of significant astrophysical background radiation. The analysis was performed on six pulsars and three pulsar candidates. The three brightest pulsars, Crab, Vela, and Geminga, were readily identified, and would have been detected independently in the EGRET data without knowledge of the pulse period. No significant pulsation was detected in the three pulsar candidates. Eighteen X-ray binaries were examined. None showed any evidence of periodicity. In addition, methods for calculating the detection threshold of periodic flux modulation were developed. The future hopes of gamma-ray astronomy lie in the development of the Gamma-ray Large Area Space Telescope, or GLAST. Part II describes the development and results of the particle track reconstruction software for a GLAST science prototype instrument beam test. The Kalman filtering method of track reconstruction is introduced and implemented. Monte Carlo simulations, very similar to those used for the full GLAST instrument, were performed to predict the instrumental response of the prototype. The prototype was tested in a gamma-ray beam at SLAC. The reconstruction software was used to determine the incident gamma-ray direction. It was found that the simulations did an excellent job of representing the actual instrument response.

B. B. Jones

2002-02-04T23:59:59.000Z

210

A Gamma-Ray Burst Bibliography, 1973-1999  

E-Print Network (OSTI)

On the average, one new publication on cosmic gamma-ray bursts enters the literature every day. The total number now exceeds 4100. I present here a complete bibliography which can be made available electronically to interested parties.

K. Hurley

1999-12-02T23:59:59.000Z

211

Observations of Gamma-Ray Bursts at Extreme Energies.  

E-Print Network (OSTI)

??Gamma-ray bursts (GRBs), thought to be produced by the core-collapse of massive stars or merging compact objects, are the most luminous events observed since the… (more)

Aune, Taylor

2012-01-01T23:59:59.000Z

212

In-beam gamma-ray spectroscopy of target fragmentation  

E-Print Network (OSTI)

E ? - E ? correlation matrix which contained the energy anddata into a 2D matrix of gamma-ray energy of clean Ge hitsenergy (belonging to a specific nucleus), we projected the matrix

2004-01-01T23:59:59.000Z

213

Redshifts of the Long Gamma-Ray Bursts  

E-Print Network (OSTI)

The low energy spectra of some gamma-ray bursts' show excess components beside the power-law dependence. The consequences of such a feature allows to estimate the gamma photometric redshift of the long gamma-ray bursts in the BATSE Catalog. There is good correlation between the measured optical and the estimated gamma photometric redshifts. The estimated redshift values for the long bright gamma-ray bursts are up to z=4, while for the the faint long bursts - which should be up to z=20 - the redshifts cannot be determined unambiguously with this method. The redshift distribution of all the gamma-ray bursts with known optical redshift agrees quite well with the BATSE based gamma photometric redshift distribution.

Z. Bagoly; I. Csabai; A. Meszaros; P. Meszaros; I. Horvath; L. G. Balazs; R. Vavrek

2007-04-06T23:59:59.000Z

214

CdZnTe technology for gamma ray detectors  

Science Conference Proceedings (OSTI)

CdZnTe detector technology has been developed at NASA Goddard for imaging and spectroscopy applications in hard x-ray and gamma ray astronomy. A CdZnTe strip detector array with capabilities for arc second imaging and spectroscopy has been built as a prototype for a space flight gamma ray burst instrument. CdZnTe detectors also have applications for medical imaging

Carl Stahle; Jack Shi; Peter Shu; Scott Barthelmy; Ann Parsons; Steve Snodgrass

1998-01-01T23:59:59.000Z

215

Relativity at Action or Gamma-Ray Bursts  

E-Print Network (OSTI)

Gamma ray Bursts (GRBs) - short bursts of few hundred keV $\\gamma$-rays - have fascinated astronomers since their accidental discovery in the sixties. GRBs were ignored by most relativists who did not expect that they are associated with any relativistic phenomenon. The recent observations of the BATSE detector on the Compton GRO satellite have revolutionized our ideas on these bursts and the picture that emerges shows that GRBs are the most relativistic objects discovered so far.

Tsvi Piran

1996-07-08T23:59:59.000Z

216

The Optical Afterglows of Gamma-Ray Bursts  

E-Print Network (OSTI)

The optical afterglows of gamma-ray bursts can be used to probe the physics, geometry, and environments of gamma-ray bursts. In this article I discuss the how spectra and photometry can be used to constrain fireball parameters, describe several types of breaks that might be observed in the optical decay, and briefly review the late-time bumps and rapid variations in optical light curves.

S. T. Holland

2002-11-18T23:59:59.000Z

217

Hyperstars - Main Origin of Short Gamma Ray Bursts?  

E-Print Network (OSTI)

The first well-localized short-duration gamma ray bursts (GRBs), GRB 050509b, GRB 050709 and GRB 050724, could have been the narrowly beamed initial spike of a burst/hyper flare of soft gamma ray repeaters (SGRs) in host galaxies at cosmological distances. Such bursts are expected if SGRs are young hyperstars, i.e. neutron stars where a considerable fraction of their neutrons have converted to hyperons and/or strange quark matter.

Arnon Dar

2005-09-09T23:59:59.000Z

218

Gamma Ray Bursts as Probes of Quantum Gravity  

E-Print Network (OSTI)

Gamma ray bursts (GRBs) are short and intense pulses of $\\gamma$-rays arriving from random directions in the sky. Several years ago Amelino-Camelia et al. pointed out that a comparison of time of arrival of photons at different energies from a GRB could be used to measure (or obtain a limit on) possible deviations from a constant speed of light at high photons energies. I review here our current understanding of GRBs and reconsider the possibility of performing these observations.

Tsvi Piran

2004-07-21T23:59:59.000Z

219

HETEROGENEITY IN SHORT GAMMA-RAY BURSTS  

SciTech Connect

We analyze the Swift/BAT sample of short gamma-ray bursts, using an objective Bayesian Block procedure to extract temporal descriptors of the bursts' initial pulse complexes (IPCs). The sample is comprised of 12 and 41 bursts with and without extended emission (EE) components, respectively. IPCs of non-EE bursts are dominated by single pulse structures, while EE bursts tend to have two or more pulse structures. The medians of characteristic timescales-durations, pulse structure widths, and peak intervals-for EE bursts are factors of {approx}2-3 longer than for non-EE bursts. A trend previously reported by Hakkila and colleagues unifying long and short bursts-the anti-correlation of pulse intensity and width-continues in the two short burst groups, with non-EE bursts extending to more intense, narrower pulses. In addition, we find that preceding and succeeding pulse intensities are anti-correlated with pulse interval. We also examine the short burst X-ray afterglows as observed by the Swift/X-Ray Telescope (XRT). The median flux of the initial XRT detections for EE bursts ({approx}6x10{sup -10} erg cm{sup -2} s{sup -1}) is {approx}>20x brighter than for non-EE bursts, and the median X-ray afterglow duration for EE bursts ({approx}60,000 s) is {approx}30x longer than for non-EE bursts. The tendency for EE bursts toward longer prompt-emission timescales and higher initial X-ray afterglow fluxes implies larger energy injections powering the afterglows. The longer-lasting X-ray afterglows of EE bursts may suggest that a significant fraction explode into denser environments than non-EE bursts, or that the sometimes-dominant EE component efficiently powers the afterglow. Combined, these results favor different progenitors for EE and non-EE short bursts.

Norris, Jay P. [Physics and Astronomy Department, University of Denver, Denver, CO 80208 (United States); Gehrels, Neil [Astroparticle Physics Laboratory, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Scargle, Jeffrey D. [Space Science and Astrobiology Division, NASA/Ames Research Center, Moffett Field, CA 94035-1000 (United States)

2011-07-01T23:59:59.000Z

220

Cluster of Gamma-ray Bursts - Image of a Source. Catalog of Clusters (Sources) of Gamma-ray Bursts  

E-Print Network (OSTI)

The clusters of gamma-ray bursts are considered which are assumed to be images of the repeated gamma-ray burst (GRB) sources. It is shown, that localization of the cosmic gamma-ray burst sources (GBS) is determined by the clusters of GRBs. About 100 candidates in sources are presented in the form of the catalog, which is compiled relying on the base of the BATSE data up to middle of 2000. Gamma-ray bursts (from 5 to 13) of a cluster that display a source do not coincide in their position. The catalog table containing basic information about the GRB sources yields the possibility to research the GBS properties and their identification. The birth of GRBs in the clusters allows predicting the appearance of GRBs both in time and space. Most general properties of the supposed GRB sources are discussed. An attempt to compile the first GRB source catalog is made.

A. V. Kuznetsov

2001-11-01T23:59:59.000Z

Note: This page contains sample records for the topic "gamma-ray logging systems" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


221

THE NEW CANGAROO TELESCOPE AND THE PROSPECT OF VHE GAMMA RAY OBSERVATION AT  

E-Print Network (OSTI)

GammaWhat about Gamma--Ray Bursts?Ray Bursts? Extremely powerful explosions happen in galaxies The Quest for Gamma Rays:The Quest for Gamma Rays: Exploring the Most Violent PlacesExploring the Most is gammaWhat is gamma--ray background light like?ray background light like? How diffuse is the gamma

Enomoto, Ryoji

222

Results from the Milagro Gamma-Ray Observatory E. Blaufuss a  

E-Print Network (OSTI)

V emission from the galactic plane, and a search for transient emission above 100 GeV from gamma ray bursts- clei (AGN), supernova remnants and gamma-ray bursts (GRB). Gamma rays are also produced when high1 Results from the Milagro Gamma-Ray Observatory E. Blaufuss a for the Milagro Collaboration

California at Santa Cruz, University of

223

Ivan De Mitri VHE Gamma Ray Astronomy 1 Very High Energy  

E-Print Network (OSTI)

~ 1/day Gamma Ray Bursts The X-ray counterpart detection with better pointing accuracy instrumentsIvan De Mitri VHE Gamma Ray Astronomy 1 Very High Energy Gamma Ray Astronomy Ivan De Mitri'Aquila, 11- Jun -2002 Photo F. Arneodo #12;Ivan De Mitri VHE Gamma Ray Astronomy 2 Seminar Outline Background

Harrison, Thomas

224

PoGO : The Polarised Gamma-ray Observer S. Larssona  

E-Print Network (OSTI)

. Recently, the detection of high linear polarisation, (80±20)%, in a gamma ray burst ob- served, this observation will have far reaching implications for models of gamma- ray bursts. Many of the X-ray and gamma-ray1 PoGO : The Polarised Gamma-ray Observer S. Larssona and M. Pearceb (for the PoGO Collaboration

Haviland, David

225

Radio emissions from terrestrial gamma-ray flashes Joseph R. Dwyer1  

E-Print Network (OSTI)

. Introduction 1.1. TGF Theory Overview [2] Terrestrial gamma-ray flashes (TGFs) are bright bursts of gamma raysRadio emissions from terrestrial gamma-ray flashes Joseph R. Dwyer1 and Steven A. Cummer2 Received frequency (RF) emissions by terrestrial gamma-ray flashes (TGFs) is developed. These radio emissions, which

Cummer, Steven A.

226

Proceedings of ICRC 2001: 1 c Copernicus Gesellschaft 2001 Status of the Milagro Gamma Ray Observatory  

E-Print Network (OSTI)

, active galactic nuclei (AGN), and gamma ray bursts (GRB). In addition, more exotic sources like Gamma Ray Observatory, located at an altitude of 8,600 feet in the Jemez Mountains of New Mexico for sources of TeV gamma rays. It is uniquely capable of search- ing for transient sources of VHE gamma rays

California at Santa Cruz, University of

227

Gamma Ray Bursts as seen by a Giant Air Shower Array  

E-Print Network (OSTI)

The potentiality of a Giant Shower Array to low energy gamma rays from gamma ray bursts is discussed. Effective areas are calculated for different scenarios and the results are encouraging. If gamma ray bursts have a spectrum which continues in the high energy gamma ray region, the Pierre Auger Observatory will be able to detect it.

C. O. Escobar; P. L. Da Silva; R. A. Vázquez

1997-12-19T23:59:59.000Z

228

MILAGRO CONSTRAINTS ON VERY HIGH ENERGY EMISSION FROM SHORT-DURATION GAMMA-RAY BURSTS  

E-Print Network (OSTI)

MILAGRO CONSTRAINTS ON VERY HIGH ENERGY EMISSION FROM SHORT-DURATION GAMMA-RAY BURSTS A. A. Abdo,1 localizations of short, hard gamma-ray bursts (GRBs) by the Swift and HETE satellites have led: bursts -- gamma rays: observations Gamma-ray bursts (GRBs) have long been classified by their durations

California at Santa Cruz, University of

229

CORRELATIONS OF PROMPT AND AFTERGLOW EMISSION IN SWIFT LONG AND SHORT GAMMA-RAY BURSTS  

E-Print Network (OSTI)

CORRELATIONS OF PROMPT AND AFTERGLOW EMISSION IN SWIFT LONG AND SHORT GAMMA-RAY BURSTS N. Gehrels,1 of prompt and afterglow emission from gamma-ray bursts (GRBs) between different spectral bands have been-limited for long events. Subject headingg: gamma rays: bursts 1. INTRODUCTION One of the longest enduring gamma-ray

Zhang, Bing

230

Realtime logging  

Science Conference Proceedings (OSTI)

This article reports that measurement-while-drilling (MWD) logging services have become an important new source of drilling and geological information on wildcats and some development wells. Sensors located within the bottomhole assembly, barely a few feet above the bit, make measurements on the formation, the borehole and the drill string itself. The MWD measurements are electronically processed and stored in the logging tool downhole. Simple MWD logging systems must wait until after tripping out of the hole for the MWD data to be downloaded from the logging tool to a surface computer in order for logs to be produced. This method is acceptable for some formation evaluation problems. But when well control, directional or completion decisions must be made, the benefit of MWD logging data is obtained only if the downhole measurements are available to the engineer in realtime.

Whittaker, A.; Kashuba, M.J.

1987-01-01T23:59:59.000Z

231

Improving the performance of log-structured file systems with adaptive block rearrangement  

Science Conference Proceedings (OSTI)

Log-Structured File System (LFS) is famous for its optimization for write performance. Because of its append-only nature, garbage collection is needed to reclaim the space occupied by the obsolete data. The cleaning overhead could significantly decrease ... Keywords: data rearrangement, garbage collection, log-structured file system

Mei-Ling Chiang; Jia-Shin Huang

2007-03-01T23:59:59.000Z

232

DOE Science Showcase - Gamma-Ray Bursts | OSTI, US Dept of Energy, Office  

Office of Scientific and Technical Information (OSTI)

Gamma-Ray Bursts Gamma-Ray Bursts Fermi Sees Record Gamma-ray Burst, May 3, 2013 Fermi Sees Record Gamma-ray Burst, May 3, 2013Credit: NASA/DOE/Fermi LAT Collection Gamma-ray bursts are short-lived bursts of gamma-ray photons observed in distant galaxies and thought to be triggered by supernovae or exploding stars. Gamma-ray bursts have been an observational and theoretical challenge since they were first observed in the 60s. Department of Energy physicists are participating in international collaborations of scientists to gain a better understanding of how gamma-ray bursts are formed and how they affect our universe. Learn about the science behind gamma-ray bursts In the OSTI Collections: Gamma Ray Bursts by Dr. William Watson, physicist, of OSTI's staff. This latest white paper includes a compilation of

233

NEW FERMI-LAT EVENT RECONSTRUCTION REVEALS MORE HIGH-ENERGY GAMMA RAYS FROM GAMMA-RAY BURSTS  

SciTech Connect

Based on the experience gained during the four and a half years of the mission, the Fermi-LAT Collaboration has undertaken a comprehensive revision of the event-level analysis going under the name of Pass 8. Although it is not yet finalized, we can test the improvements in the new event reconstruction with the special case of the prompt phase of bright gamma-ray bursts (GRBs), where the signal-to-noise ratio is large enough that loose selection cuts are sufficient to identify gamma rays associated with the source. Using the new event reconstruction, we have re-analyzed 10 GRBs previously detected by the Large Area Telescope (LAT) for which an X-ray/optical follow-up was possible and found four new gamma rays with energies greater than 10 GeV in addition to the seven previously known. Among these four is a 27.4 GeV gamma ray from GRB 080916C, which has a redshift of 4.35, thus making it the gamma ray with the highest intrinsic energy ({approx}147 GeV) detected from a GRB. We present here the salient aspects of the new event reconstruction and discuss the scientific implications of these new high-energy gamma rays, such as constraining extragalactic background light models, Lorentz invariance violation tests, the prompt emission mechanism, and the bulk Lorentz factor of the emitting region.

Atwood, W. B. [Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); Baldini, L. [Universita di Pisa and Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Bregeon, J.; Pesce-Rollins, M.; Sgro, C.; Tinivella, M. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Bruel, P. [Laboratoire Leprince-Ringuet, Ecole polytechnique, CNRS/IN2P3, Palaiseau (France); Chekhtman, A. [Center for Earth Observing and Space Research, College of Science, George Mason University, Fairfax, VA 22030 (United States); Cohen-Tanugi, J. [Laboratoire Univers et Particules de Montpellier, Universite Montpellier 2, CNRS/IN2P3, F-34095 Montpellier (France); Drlica-Wagner, A.; Omodei, N.; Rochester, L. S.; Usher, T. L. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Granot, J. [Department of Natural Sciences, The Open University of Israel, 1 University Road, P.O. Box 808, Ra'anana 43537 (Israel); Longo, F. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Razzaque, S. [Department of Physics, University of Johannesburg, Auckland Park 2006 (South Africa); Zimmer, S., E-mail: melissa.pesce.rollins@pi.infn.it, E-mail: nicola.omodei@stanford.edu, E-mail: granot@openu.ac.il [Department of Physics, Stockholm University, AlbaNova, SE-106 91 Stockholm (Sweden)

2013-09-01T23:59:59.000Z

234

(DOI: will be inserted by hand later) Light Curves of Swift Gamma Ray Bursts  

E-Print Network (OSTI)

Abstract. Recent observations from the Swift gamma ray burst explorer indicate that a large fraction of gamma ray bursts are characterized by a canonical behaviour of the X-ray afterglows. We present an effective theory which allows us to account for X-ray light curves of both gamma ray bursts and X-ray rich flashes. We propose that gamma ray bursts originate from massive magnetic powered pulsars. Key words. gamma-rays: bursts 1.

Paolo Cea

2006-01-01T23:59:59.000Z

235

Testing Gamma-Ray Burst Jet Structure with the Distribution of Gamma-Ray Energy Release  

E-Print Network (OSTI)

We present a general method for testing gamma-ray burst (GRB) jet structure and carry out a comprehensive analysis about the prevalent jet structure models. According to the jet angular energy distribution, we can not only derive the expected distribution of the GRB isotropic-equivalent energy release for any possible jet structure, but also obtain a two-dimensional distribution including redshift z. By using the Kolmogorov-Smirnov test we compare the predicted distribution with the observed sample, and find that the power-law structured jet model is most consistent with the current sample and that the uniform jet model is also plausible. However, this conclusion is tentative because of the small size and the inhomogeneity of this sample. Future observations (e.g., Swift) will provide a larger and less biased sample for us to make a robust conclusion by using the procedure proposed in this paper.

L. Xu; X. F. Wu; Z. G. Dai

2005-08-15T23:59:59.000Z

236

Geophysical logging case history of the Raft River geothermal system, Idaho  

Open Energy Info (EERE)

Geophysical logging case history of the Raft River geothermal system, Idaho Geophysical logging case history of the Raft River geothermal system, Idaho Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Report: Geophysical logging case history of the Raft River geothermal system, Idaho Details Activities (1) Areas (1) Regions (0) Abstract: Drilling to evaluate the geothermal resource in the Raft River Valley began in 1974 and resulted in the discovery of a geothermal reservoir at a depth of approximately 1523 m (500 ft). Several organizations and companies have been involved in the geophysical logging program. There is no comprehensive report on the geophysical logging, nor has there been a complete interpretation. The objectives of this study are to make an integrated interpretation of the available data and compile a case history. Emphasis has been on developing a simple interpretation

237

Application of oil-field well log interpretation techniques to the Cerro Prieto Geothermal Field  

DOE Green Energy (OSTI)

An example is presented of the application of oil-field techniques to the Cerro Prieto Field, Mexico. The lithology in this field (sand-shale lithology) is relatively similar to oil-field systems. The study was undertaken as a part of the first series of case studies supported by the Geothermal Log Interpretation Program (GLIP) of the US Department of Energy. The suites of logs for individual wells were far from complete. This was partly because of adverse borehole conditions but mostly because of unavailability of high-temperature tools. The most complete set of logs was a combination of Dual Induction Laterolog, Compensated Formation Density Gamma Ray, Compensated Neutron Log, and Saraband. Temperature data about the wells were sketchy, and the logs had been run under pre-cooled mud condition. A system of interpretation consisting of a combination of graphic and numerical studies was used to study the logs. From graphical studies, evidence of hydrothermal alteration may be established from the trend analysis of SP (self potential) and ILD (deep induction log). Furthermore, the cross plot techniques using data from density and neutron logs may help in establishing compaction as well as rock density profile with depth. In the numerical method, R/sub wa/ values from three different resistivity logs were computed and brought into agreement. From this approach, values of formation temperature and mud filtrate resistivity effective at the time of logging were established.

Ershaghi, I.; Phillips, L.B.; Dougherty, E.L.; Handy, L.L.

1979-10-01T23:59:59.000Z

238

Gamma-Ray Bursts from Radio-Quiet Quasars  

E-Print Network (OSTI)

We study positional coincidences between gamma-ray bursts in the BATSE 3B catalogue and quasars/AGN taken from the Veron-Cetty & Veron compilation. For most classes of AGN, for BL Lac objects and for radio-loud quasars, we find no excess coincidences above random expectation, and we give upper limits for their burst emission rate. However, surprising evidence is found for a positional correlation between gamma-ray bursts and radio-quiet quasars. A total of 134 selected bursts with a position error radius 99.7% to be associated with each other. An analysis of a smaller sample of well-localized interplanetary network gamma-ray burst positions supports this result. This correlation strongly favours the cosmological origin of gamma-ray bursts and enables to estimate its distance scale. The average luminosity of those gamma-ray bursts which we associate directly with radio-quiet quasars is of the order of 4*10^52 erg (assuming isotropic emission).

N. Schartel; H. Andernach; J. Greiner

1996-12-16T23:59:59.000Z

239

On the nature of gamma-ray burst time dilations  

E-Print Network (OSTI)

The recent discovery that faint gamma-ray bursts are stretched in time relative to bright ones has been interpreted as support for cosmological distances: faint bursts have their durations redshifted relative to bright ones. It was pointed out, however, that the relative time stretching can also be produced by an intrinsic correlation between duration and luminosity of gamma-ray bursts in a nearby, bounded distribution. While both models can explain the average amount of time stretching, we find a difference between them in the way the duration distribution of faint bursts deviates from that of bright ones, assuming the luminosity function of gamma-ray bursts is independent of distance. This allows us to distinguish between these two broad classes of model on the basis of the duration distributions of gamma-ray bursts, leading perhaps to an unambiguous determination of the distance scale of gamma-ray bursts. We apply our proposed test to the second BATSE catalog and conclude, with some caution, that the data favor a cosmological interpretation of the time dilation.

Ralph A. M. J. Wijers; Bohdan Paczy?ski

1994-08-02T23:59:59.000Z

240

Diffuse gamma-ray emission: Galactic and extragalactic  

E-Print Network (OSTI)

Here is reviewed our current understanding of Galactic and extragalactic diffuse gamma-ray emission. The spectrum of the extragalactic gamma-ray background above 30 MeV can be well described by a power law with photon index s=2.1. In the 2-10 MeV range a preliminary analysis of COMPTEL data indicates a lower intensity than previously found, with no evidence for an MeV bump. Most of the models of a truly diffuse background seem to be in conflict with the observed spectrum. Though AGN are the most likely input from discrete sources, two independent attempts to model the high energy background as the superposition of unresolved AGN indicate that AGN underproduce the observed intensity. Therefore the origin of the extragalactic gamma-ray background is still unknown. The Galactic diffuse gamma-ray continuum is more intense than expected both at very low energies (energies (> 1 GeV). The published models for these excesses all involve cosmic ray electron interactions. While the low energy excess may have something to do with in-situ acceleration of electrons, the excess at high energies may be understood if the sources of cosmic ray electrons are discrete. The measured energy spectrum of the diffuse Galactic gamma-ray continuum radiation thus may provide new insights into the acceleration of cosmic rays.

Martin Pohl

1998-07-27T23:59:59.000Z

Note: This page contains sample records for the topic "gamma-ray logging systems" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


241

The WISE Gamma-Ray Strip Parametrization: The Nature of the Gamma-Ray Active Galactic Nuclei of Uncertain Type  

SciTech Connect

Despite the large number of discoveries made recently by Fermi, the origins of the so called unidentified {gamma}-ray sources remain unknown. The large number of these sources suggests that among them there could be a population that significantly contributes to the isotropic gamma-ray background and is therefore crucial to understand their nature. The first step toward a complete comprehension of the unidentified {gamma}-ray source population is to identify those that can be associated with blazars, the most numerous class of extragalactic sources in the {gamma}-ray sky. Recently, we discovered that blazars can be recognized and separated from other extragalactic sources using the infrared (IR) WISE satellite colors. The blazar population delineates a remarkable and distinctive region of the IR color-color space, the WISE blazar strip. In particular, the subregion delineated by the {gamma}-ray emitting blazars is even narrower and we named it as the WISE Gamma-ray Strip (WGS). In this paper we parametrize the WGS on the basis of a single parameter s that we then use to determine if {gamma}-ray Active Galactic Nuclei of the uncertain type (AGUs) detected by Fermi are consistent with the WGS and so can be considered blazar candidates. We find that 54 AGUs out of a set 60 analyzed have IR colors consistent with the WGS; only 6 AGUs are outliers. This result implies that a very high percentage (i.e., in this sample about 90%) of the AGUs detected by Fermi are indeed blazar candidates.

Massaro, F.; /SLAC; D'Abrusco, R.; /Harvard-Smithsonian Ctr. Astrophys.; Tosti, G.; /Perugia U. /INFN, Perugia; Ajello, M.; /SLAC; Gasparrini, D.; /ESRIN, Frascati; Grindlay, J.E.; Smith, Howard A.; /Harvard-Smithsonian Ctr. Astrophys.

2012-04-02T23:59:59.000Z

242

A Combined Neutron and Gamma-Ray Multiplicity Counter Based on Liquid Scintillation Detectors  

Science Conference Proceedings (OSTI)

Multiplicity counters for neutron assay have been extensively used in materials control and accountability for nonproliferation and nuclear safeguards. Typically, neutron coincidence counters are utilized in these fields. In this work, we present a measurement system that makes use not only of neutron (n) multiplicity counting but also of gamma-ray (g) multiplicity counting and the combined higher-order multiples containing both neutrons and gamma rays. The benefit of this approach is in using both particle types available from the sample, leading to a reduction in measurement times needed when using more measurables. We present measurement results of n, g, nn, ng, gg, nnn, nng, ngg, and ggg multiples emitted by Mixed-Oxide (MOX) samples measured at Idaho National Laboratory (INL). The MOX measurement is compared to initial validation of the detection system done using a 252Cf source. The dual radiation measuring system proposed here uses extra measurables to improve the statistics when compared to a neutron-only system and allows for extended analysis and interpretation of sample parameters. New challenges such as the effect of very high intrinsic gamma-ray sources in the case of MOX samples is discussed. Successful measurements of multiples rates can be performed also when using high-Z shielding.

Andreas Enqvist; Marek Flaska; Jennifer Dolan; David L. Chichester; Sara A. Pozzi

2011-10-01T23:59:59.000Z

243

Gamma-Ray Bursts and Topology of the Universe  

E-Print Network (OSTI)

In this letter we propose a physical explanation for recently reported correlations between pairs of close and antipodal gamma-ray bursts from publicly available BATSE catalogue. Our model is based on the cosmological scenario in which bursters are located at cosmological distances of order of 0.5--2~Gpc. Observed distribution of gamma-ray bursts strongly suports this assumption. If so gamma-ray bursts may provide a very good probe for investigating the topological structure of the Universe. We notice that correlation between antipodal events may in fact indicate that we live in the so called Ellis' small universe which has Friedman-Roberston-Walker metric structure and nontrivial topology.

Marek Biesiada

1993-10-04T23:59:59.000Z

244

Gamma-ray Pulsars in a Modified Polar Cap Scenario  

E-Print Network (OSTI)

We present a polar-cap model which incorporates a likely acceleration of Sturrock pairs with their subsequent contribution to gamma-ray luminosity L_gamma. This model reproduces L_gamma for seven pulsars detected with Compton Gamma Ray Observatory experiments, avoiding at the same time the problem of the empirical gamma-ray death line of Arons (1996). Also, we estimate the efficiency of reversing newly created positrons by residual longitudinal electric field. Over the wide range of spin-down luminosity values the predicted polar-cap X-ray luminosity L_X(pc) goes as L_sd^{0.6}. Model calculations for B0823+26, B0950+08, B1929+10, and J0437-4715 are compared with existing observational constraints on thermal X-ray components.

B. Rudak; J. Dyks

1997-10-22T23:59:59.000Z

245

Fermi GBM Observations of Terrestrial Gamma-ray Flashes  

Science Conference Proceedings (OSTI)

Terrestrial Gamma-ray Flashes are short pulses of energetic radiation associated with thunderstorms and lightning. While the Gamma-ray Burst Monitor (GBM) on Fermi was designed to observe gamma-ray bursts, its large BGO detectors are excellent for observing TGFs. Using GBM, TGF pulses are seen to either be symmetrical or have faster rise time than fall times. Some TGFs are resolved into double, partially overlapping pulses. Using ground-based radio observations of lightning from the World Wide Lightning Location Network (WWLLN), TGFs and their associated lightning are found to be simultaneous to {approx_equal}40 {mu} s. The lightning locations are typically within 300 km of the sub-spacecraft point.

Briggs, Michael S. [CSPAR, NSSTC, 320 Sparkman Drive, Huntsville, AL 35805 (United States)

2011-09-21T23:59:59.000Z

246

AGN models for the X and gamma-ray backgrounds  

E-Print Network (OSTI)

The origin of the X-ray background spectral intensity has been a long standing problem in high energy astrophysics research. Deep X-ray surveys carried out with ROSAT and ASCA combined with the broad band spectral results of Ginga and BeppoSAX satellites strongly support the hypothesis that the bulk of the X-ray background is due to the integrated contribution of discrete sources (mainly AGNs). At higher energies the unexpected findings of the Compton Gamma Ray Observatory indicate that also the gamma-ray background is likely to be due to AGNs. I will discuss AGN--based models for the high energy backgrounds and how future observations will improve our understanding of the X and gamma-ray backgrounds and of the physics and evolution of AGNs.

Andrea Comastri

1998-12-16T23:59:59.000Z

247

Gamma-ray spectrometer utilizing xenon at high pressure  

SciTech Connect

A prototype gamma-ray spectrometer utilizing xenon gas near the critical point (166{degrees}C, 58 atm) is under development. The spectrometer will function as a room-temperature ionization chamber detecting gamma rays in the energy range 100 keV2 MeV, with an energy resolution intermediate between semiconductor (Ge) and scintillation (NaI) spectrometers. The energy resolution is superior to that of a NaI scintillation spectrometer by a substantial margin (approximately a factor 5), and accordingly, much more information can be extracted from a given gamma-ray spectrum. Unlike germanium detectors, the spectrometer possesses the capability for sustained operation under ambient temperature conditions without a requirement for liquid nitrogen.

Smith, G.C.; Mahler, G.J.; Yu, B.; Kane, W.R. [Brookhaven National Lab., Upton, NY (United States); Markey, J.K. [Yale Univ., New Haven, CT (United States). School of Medicine

1994-08-01T23:59:59.000Z

248

High Energy Gamma Rays from Protons Hitting Compact Objects  

E-Print Network (OSTI)

In a previous paper the spectrum of positrons produced by matter initially at rest falling onto a massive compact object was calculated. In this paper this calculation is generalized to obtain both the spectrum of in-flight positron annihilation and pi0 decay gamma rays produced when protons with a cosmic ray-like spectrum hit the surface. The resulting pi0 decay gamma ray spectrum reflects the high energy proton energy spectrum, and is largely independent of the mass of the compact object. One notable prediction for all compact objects is a dip in the spectrum below 70 MeV. As applied to the 10^6 solar mass massive compact object near to the center of our galaxy, our theory shows promise for explaining the gamma rays coming from the galactic center as observed by both the Compton satellite and HESS ground based array.

J. Barbieri; G. Chapline

2008-06-09T23:59:59.000Z

249

Are Durations of Weak Gamma-Ray Bursts Reliable?  

E-Print Network (OSTI)

Simulations in the GUSBAD Catalog of gamma-ray bursts suggest that the apparent duration of a burst decreases as its amplitude is decreased. We see no evidence for this effect in the BATSE catalog. We show that for a burst at the detection limit, the typical signal-to-noise ratio at the edges of the T90 duration is around 1.5, suggesting that T90 must be quite uncertain. The situation for T50 is less unfavorable. Simulations using the exact procedure to derive the durations listed in the BATSE catalog would be useful in quantifying the effect. PACS 95.85.Pw – gamma-ray. PACS 98.70.Rz – gamma-ray bursts.

Maarten Schmidt

2005-01-01T23:59:59.000Z

250

Gamma Ray Bursts, The Principle of Relative Locality and Connection Normal Coordinates  

E-Print Network (OSTI)

The launch of the Fermi telescope in 2008 opened up the possibility of measuring the energy dependence of the speed of light by considering the time delay in the arrival of gamma ray bursts emitted simultaneously from very distant sources.The expected time delay between the arrival of gamma rays of significantly different energies as predicted by the framework of relative locality has already been calculated in Riemann normal coordinates. In the following, we calculate the time delay in more generality and then specialize to the connection normal coordinate system as a check that the results are coordinate independent. We also show that this result does not depend on the presence of torsion.

A. E. McCoy

2012-01-04T23:59:59.000Z

251

EPISODIC JETS AS THE CENTRAL ENGINE OF GAMMA-RAY BURSTS  

SciTech Connect

Most gamma-ray bursts (GRBs) have erratic light curves, which demand that the GRB central engine launches an episodic outflow. Recent Fermi observations of some GRBs indicate a lack of the thermal photosphere component as predicted by the baryonic fireball model, which suggests a magnetic origin of GRBs. Given that powerful episodic jets have been observed along with continuous jets in other astrophysical black hole systems, here we propose an intrinsically episodic, magnetically dominated jet model for the GRB central engine. Accumulation and eruption of free magnetic energy in the corona of a differentially rotating, turbulent accretion flow around a hyperaccreting black hole lead to ejections of episodic, magnetically dominated plasma blobs. These blobs are accelerated magnetically, collide with each other at large radii, trigger rapid magnetic reconnection and turbulence, efficient particle acceleration, and radiation, and power the observed episodic prompt gamma-ray emission from GRBs.

Yuan Feng [Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China); Zhang Bing, E-mail: fyuan@shao.ac.cn, E-mail: zhang@physics.unlv.edu [Department of Physics and Astronomy, University of Nevada Las Vegas, Las Vegas, NV 89154 (United States)

2012-09-20T23:59:59.000Z

252

VERITAS Observations of the gamma-Ray Binary LS I +61 303  

E-Print Network (OSTI)

LS I +61 303 is one of only a few high-mass X-ray binaries currently detected at high significance in very high energy gamma-rays. The system was observed over several orbital cycles (between September 2006 and February 2007) with the VERITAS array of imaging air-Cherenkov telescopes. A signal of gamma-rays with energies above 300 GeV is found with a statistical significance of 8.4 standard deviations. The detected flux is measured to be strongly variable; the maximum flux is found during most orbital cycles at apastron. The energy spectrum for the period of maximum emission can be characterized by a power law with a photon index of Gamma=2.40+-0.16_stat+-0.2_sys and a flux above 300 GeV corresponding to 15-20% of the flux from the Crab Nebula.

V. A. Acciari; M. Beilicke; G. Blaylock; S. M. Bradbury; J. H. Buckley; V. Bugaev; Y. Butt; K. L. Byrum; O. Celik; A. Cesarini; L. Ciupik; Y. C. K. Chow; P. Cogan; P. Colin; W. Cui; M. K. Daniel; C. Duke; T. Ergin; A. D. Falcone; S. J. Fegan; J. P. Finley; P. Fortin; L. F. Fortson; D. Gall; K. Gibbs; G. H. Gillanders; J. Grube R. Guenette; D. Hanna; E. Hays; J. Holder; D. Horan; S. B. Hughes; C. M. Hui; T. B. Humensky; P. Kaaret; D. B. Kieda; J. Kildea; A. Konopelko; H. Krawczynski; F. Krennrich; M. J. Lang; S. LeBohec; K. Lee; G. Maier; A. McCann; M. McCutcheon; J. Millis; P. Moriarty; R. Mukherjee; T. Nagai; R. A. Ong; D. Pandel; J. S. Perkins; F. Pizlo; M. Pohl; J. Quinn; K. Ragan; P. T. Reynolds; H. J. Rose; M. Schroedter; G. H. Sembroski; A. W. Smith; D. Steele; S. P. Swordy; J. A. Toner; L. Valcarcel; V. V. Vassiliev; R. Wagner; S. P. Wakely; J. E. Ward; T. C. Weekes; A. Weinstein; R. J. White; D. A. Williams; S. A. Wissel; M. Wood; B. Zitzer

2008-02-18T23:59:59.000Z

253

Diffuse Gamma-Rays from Local Group Galaxies  

E-Print Network (OSTI)

Diffuse gamma-ray radiation in galaxies is produced by cosmic ray interactions with the interstellar medium. With the completion of EGRET observations, the only extragalactic object from which there has been a positive detection of diffuse gamma-ray emission is the Large Magellanic Cloud. We systematically estimate the expected diffuse gamma-ray flux from Local Group galaxies, and determine their detectability by new generation gamma-ray observatories such as GLAST. For each galaxy, the expected gamma-ray flux depends only on its total gas content and its cosmic ray flux. We present a method for calculating cosmic ray flux in these galaxies in terms of the observed rate of supernova explosions, where cosmic ray acceleration is believed to take place. The difficulty in deriving accurate supernova rates from observational data is a dominant uncertainty in our calculations. We estimate the gamma-ray flux for Local Group galaxies and find that our predictions are consistent with the observations for the LMC and with the observational upper limits for the Small Magellanic Cloud and M31. Both the Andromeda galaxy, with a flux of $\\sim 1.0 \\times 10^{-8}$ photons sec$^{-1}$ cm$^{-2}$ above 100 MeV, and the SMC, with a flux of $\\sim 1.7 \\times 10^{-8}$ photons sec$^{-1}$ cm$^{-2}$ above 100 MeV, are expected to be observable by GLAST. M33 is at the limit of detectability with a flux of $\\sim 0.11 \\times 10^{-8}$ sec$^{-1}$ cm$^{-2}$. Other Local Group galaxies are at least two orders of magnitude below GLAST sensitivity.

Vasiliki Pavlidou; Brian D. Fields

2001-05-11T23:59:59.000Z

254

X-ray afterglows from gamma-ray bursts  

E-Print Network (OSTI)

We consider possible interpretations of the recently detected X- ray afterglow from the gamma-ray burst source GRB 970228. Cosmological and Galactic models of gamma-ray bursts predict different flux and spectral evolution of X-ray afterglows. We show that models based on adiabatic expansion of relativistic forward shocks require very efficient particle energization or post-burst re-acceleration during the expansion. Cooling neutron star models predict a very distinctive spectral and flux evolution that can be tested in current X-ray data.

M. Tavani

1997-03-24T23:59:59.000Z

255

Present and future gamma-ray burst experiments  

E-Print Network (OSTI)

Gamma-ray burst counterpart studies require small, prompt error boxes. Today, there are several missions which can provide them: BeppoSAX, the Rossi X-Ray Timing Explorer, and the 3rd Interplanetary Network. In the near future, HETE-II, a possible extended Interplanetary Network, and INTEGRAL will operate in this capacity. In the longer term future, a dedicated gamma-ray burst MIDEX mission may fly. The capabilities of these missions are reviewed, comparing the number of bursts, the rapidity of the localizations, and the error box sizes.

K. Hurley

1998-12-21T23:59:59.000Z

256

A Gamma-Ray Bursts' Fluence-Duration Correlation  

E-Print Network (OSTI)

We present an analysis indicating that there is a correlation between the fluences and the durations of gamma-ray bursts, and provide arguments that this reflects a correlation between the total emitted energies and the intrinsic durations. For the short (long) bursts the total emitted energies are roughly proportional to the first (second) power of the intrinsic duration. This difference in the energy-duration relationship is statistically significant, and may provide an interesting constraint on models aiming to explain the short and long gamma-ray bursts.

Istvan Horvath; Lajos G. Balazs; Peter Meszaros; Zsolt Bagoly; Attila Meszaros

2005-08-01T23:59:59.000Z

257

Correlation between Gamma-Ray bursts and Gravitational Waves  

E-Print Network (OSTI)

The cosmological origin of $\\gamma$-ray bursts (GRBs) is now commonly accepted and, according to several models for the central engine, GRB sources should also emit at the same time gravitational waves bursts (GWBs). We have performed two correlation searches between the data of the resonant gravitational wave detector AURIGA and GRB arrival times collected in the BATSE 4B catalog. No correlation was found and an upper limit \\bbox{$h_{\\text{RMS}} \\leq 1.5 \\times 10^{-18}$} on the averaged amplitude of gravitational waves associated with $\\gamma$-ray bursts has been set for the first time.

P. Tricarico; A. Ortolan; A. Solaroli; G. Vedovato; L. Baggio; M. Cerdonio; L. Taffarello; J. Zendri; R. Mezzena; G. A. Prodi; S. Vitale; P. Fortini; M. Bonaldi; P. Falferi

2001-01-05T23:59:59.000Z

258

Angular Signatures of Dark Matter in the Diffuse Gamma Ray Background  

E-Print Network (OSTI)

Dark matter annihilating in our Galaxy's halo and elsewhere in the universe is expected to generate a diffuse flux of gamma rays, potentially observable with next generation satellite-based experiments, such as GLAST. In this article, we study the signatures of dark matter in the angular distribution of this radiation, in particular the deterministic ones. Pertaining to the extragalactic contribution, we discuss the effect of the motion of the solar system with respect to the cosmological rest frame, and anisotropies due to the structure of our local universe. For the gamma ray flux from dark matter in our own Galactic halo, we discuss the effects of the offset position of the solar system, the Compton-Getting effect, the asphericity of the Milky Way halo, and the signatures of nearby substructure. We explore the prospects for the detection of these features by the GLAST satellite and find that, if ~10% or more of the diffuse gamma ray background observed by EGRET is the result of dark matter annihilations, then GLAST should be sensitive to anisotropies at the sub-percent level. Such precision would be sufficient to detect many, if not all, of the signatures discussed in this paper.

Dan Hooper; Pasquale D. Serpico

2007-02-12T23:59:59.000Z

259

NO CORRELATION BETWEEN HOST GALAXY METALLICITY AND GAMMA-RAY ENERGY RELEASE FOR LONG-DURATION GAMMA-RAY BURSTS  

Science Conference Proceedings (OSTI)

We compare the redshifts, host galaxy metallicities, and isotropic (E{sub {gamma}},iso) and beaming-corrected (E{sub {gamma}}) gamma-ray energy release of 16 long-duration gamma-ray bursts (LGRBs) at z gamma}},iso, or E{sub {gamma}}. These results are at odds with previous theoretical and observational predictions of an inverse correlation between gamma-ray energy release and host metallicity, as well as the standard predictions of metallicity-driven wind effects in stellar evolutionary models. We consider the implications that these results have for LGRB progenitor scenarios, and discuss our current understanding of the role that metallicity plays in the production of LGRBs.

Levesque, Emily M.; Kewley, Lisa J. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Soderberg, Alicia M.; Berger, Edo, E-mail: emsque@ifa.hawaii.ed, E-mail: kewley@ifa.hawaii.ed, E-mail: asoderbe@cfa.harvard.ed, E-mail: eberger@cfa.harvard.ed [Smithsonian Astrophysical Observatory, 60 Garden St., MS-20, Cambridge, MA 02138 (United States)

2010-12-10T23:59:59.000Z

260

The lowest-mass stellar black holes: catastrophic death of neutron stars in gamma-ray bursts  

E-Print Network (OSTI)

Mergers of double neutron stars are considered the most likely progenitors for short gamma-ray bursts. Indeed such a merger can produce a black hole with a transient accreting torus of nuclear matter (Lee & Ramirez-Ruiz 2007, Oechslin & Janka 2006), and the conversion of a fraction of the torus mass-energy to radiation can power a gamma-ray burst (Nakar 2006). Using available binary pulsar observations supported by our extensive evolutionary calculations of double neutron star formation, we demonstrate that the fraction of mergers that can form a black hole -- torus system depends very sensitively on the (largely unknown) maximum neutron star mass. We show that the available observations and models put a very stringent constraint on this maximum mass under the assumption that a black hole formation is required to produce a short gamma-ray burst in a double neutron star merger. Specifically, we find that the maximum neutron star mass must be within 2 - 2.5 Msun. Moreover, a single unambiguous measurement of a neutron star mass above 2.5 Msun would exclude a black hole -- torus central engine model of short gamma-ray bursts in double neutron star mergers. Such an observation would also indicate that if in fact short gamma-ray bursts are connected to neutron star mergers, the gamma-ray burst engine is best explained by the lesser known model invoking a highly magnetized massive neutron star (e.g., Usov 1992; Kluzniak & Ruderman 1998; Dai et al. 2006; Metzger, Quataert & Thompson 2007).

K. Belczynski; R. O'Shaughnessy; V. Kalogera; F. Rasio; R. Taam; T. Bulik

2007-12-06T23:59:59.000Z

Note: This page contains sample records for the topic "gamma-ray logging systems" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


261

Active Detection and Imaging of Nuclear Materials with High-Brightness Gamma Rays  

Science Conference Proceedings (OSTI)

A Compton scattering {gamma}-ray source, capable of producing photons with energies ranging from 0.1 MeV to 0.9 MeV has been commissioned and characterized, and then used to perform nuclear resonance fluorescence (NRF) experiments. The performances of the two laser systems (one for electron production, one for scattering), the electron photoinjector, and the linear accelerator are also detailed, and {gamma}-ray results are presented. The key source parameters are the size (0.01 mm{sup 2}), horizontal and vertical divergence (6 x 10 mrad{sup 2}), duration (10 ps), spectrum and intensity (10{sup 5} photons/shot). These parameters are summarized by the peak brightness, 1.5 x 10{sup 15} photons/mm{sup 2}/mrad{sup 2}/s/0.1% bandwidth, measured at 478 keV. Additional measurements of the flux as a function of the timing difference between the drive laser pulse and the relativistic photo-electron bunch, {gamma}-ray beam profile, and background evaluations are presented. These results are systematically compared to theoretical models and computer simulations. NRF measurements performed on {sup 7}Li in LiH demonstrate the potential of Compton scattering photon sources to accurately detect isotopes in situ.

Barty, C J; Gibson, D J; Albert, F; Anderson, S G; Anderson, G G; Betts, S M; Berry, R D; Fisher, S E; Hagmann, C A; Johnson, M S; Messerly, M J; Phan, H H; Semenov, V A; Shverdin, M Y; Tremaine, A M; Hartemann, F V; Siders, C W; McNabb, D P

2009-02-26T23:59:59.000Z

262

X-ray Spectral Properties of Gamma-Ray Bursts  

E-Print Network (OSTI)

We summarize the spectral characteristics of a sample of 22 bright gamma-ray bursts detected with the gamma-ray burst sensors aboard the satellite Ginga. This instrument employed a proportional and scintillation counter to provide sensitivity to photons in the 2 - 400 keV range, providing a unique opportunity to characterize the largely unexplored X-ray properties of gamma-ray bursts. The photon spectra of the Ginga bursts are well described by a low energy slope, a bend energy, and a high energy slope. In the energy range where they can be compared, this result is consistent with burst spectral analyses obtained from the BATSE experiment aboard the Compton Observatory. However, below 20 keV we find evidence for a positive spectral number index in approximately 40% of our burst sample, with some evidence for a strong rolloff at lower energies in a few events. There is a correlation (Pearson's r = -0.62) between the low energy slope and the bend energy. We find that the distribution of spectral bend energies extends below 10 keV. The observed ratio of energy emitted in the X-rays relative to the gamma-rays can be much larger than a few percent and, in fact, is sometimes larger than unity. The average for our sample is 24%.

T. E. Strohmayer; E. E. Fenimore; T. Murakami; A. Yoshida

1997-12-18T23:59:59.000Z

263

A Gamma-Ray Burst Bibliography, 1973-2001  

E-Print Network (OSTI)

On the average, 1.5 new publications on cosmic gamma-ray bursts enter the literature every day. The total number now exceeds 5300. I describe here a relatively complete bibliography which is on the web, and which can be made available electronically in various formats.

K. Hurley

2002-01-18T23:59:59.000Z

264

Gamma Ray Bursts as Probes of the First Stars  

E-Print Network (OSTI)

The redshift where the first stars formed is an important and unknown milestone in cosmological structure formation. The evidence linking gamma ray bursts (GRBs) with star formation activity implies that the first GRBs occurred shortly after the first stars formed. Gamma ray bursts and their afterglows may thus offer a unique probe of this epoch, because they are bright from gamma ray to radio wavelengths and should be observable to very high redshift. Indeed, our ongoing near-IR followup programs already have the potential to detect bursts at redshift z ~ 10. In these proceedings, we discuss two distinct ways of using GRBs to probe the earliest star formation. First, direct GRB counts may be used as a proxy for star formation rate measurements. Second, high energy cutoffs in the GeV spectra of gamma ray bursts due to pair production with high redshift optical and ultraviolet background photons contain information on early star formation history. The second method is observationally more demanding, but also more rewarding, because each observed pair creation cutoff in a high redshift GRB spectrum will tell us about the integrated star formation history prior to the GRB redshift.

James E. Rhoads

2001-11-01T23:59:59.000Z

265

Can Fireball or Firecone Models Explain Gamma Ray Bursts?  

E-Print Network (OSTI)

The observed afterglows of gamma ray bursts, in particular that of GRB 970228 six months later, seem to rule out relativistic fireballs and relativistic firecones driven by merger or accretion induced collapse of compact stellar objects in galaxies as the origin of GRBs. GRBs can be produced by superluminal jets from such events.

Arnon Dar

1997-09-24T23:59:59.000Z

266

The efficiency of gamma-ray emission from pulsars  

E-Print Network (OSTI)

We present a modified scenario of gamma-ray emission from pulsars within the framework of polar cap models. Our model incorporates possible acceleration of electron-positron pairs created in magnetospheres, and their subsequent contribution to gamma-ray luminosity L_\\gamma. It also reproduces the empirical trend in L_\\gamma for seven pulsars detected with Compton Gamma Ray Observatory (CGRO) experiments. At the same time it avoids basic difficulties (Nel et al. 1996, Arons 1996) faced by theoretical models when confronted with observational constraints. We show that the classical and millisecond pulsars form two distinct branches in the L_gamma - L_sd diagram (where L_sd is the spin-down luminosity). In particular, we explain why the millisecond pulsar J0437-4715 has not been detected with any of the CGRO instruments despite its very high position in the ranking list of spin-down fluxes (i.e. L_sd/D^2, where D is a distance). The gamma-ray luminosity predicted for this particular object is about one order of magnitude below the upper limit set by EGRET.

B. Rudak; J. Dyks

1997-10-22T23:59:59.000Z

267

Gamma-Ray Exposure Rate Distribution in a Steam Generator  

Science Conference Proceedings (OSTI)

Gamma-ray exposure rate measurements were made with thermoluminescent dosimeters to determine the relative contribution of various surface areas in a steam generator to the overall radiation levels. The measurements were compared with analytic predictions based on discrete ordinates and point kernel techniques, and assessments of the radiation source inventory of the various surfaces were developed.

1983-05-01T23:59:59.000Z

268

The Pionic Contribution to Diffuse Gamma Rays: Upper Limits  

E-Print Network (OSTI)

Diffuse gamma rays probe the highest-energy processes at the largest scales. Here we derive model-independent constraints on the hadronic contribution to the Galactic and extragalactic gamma-ray spectra in the energy range 50 MeV < E_gamma < 10 GeV. The hadronic component is dominated by emission from neutral pions, with a characteristic spectrum symmetric about m_{pi^0}/2. We exploit the well-defined properties of the pion decay spectrum to quantify the maximum pionic fraction of the observed gamma-ray intensity. We find that the Galactic spectrum above 30 MeV can be at most about 50% pionic. The maximum pionic contribution to the extragalactic spectrum is energy dependent; it also depends on the redshift range over which the sources are distributed, ranging from as low as about 20% for pions generated very recently, to as much as 90% if the pions are generated around redshift 10. The implications of these constraints for models of gamma-ray and neutrino emission are briefly discussed.

Tijana Prodanovic; Brian D. Fields

2004-03-12T23:59:59.000Z

269

Cosmic Rays and Gamma Ray Bursts From Microblazars  

E-Print Network (OSTI)

Highly relativistic jets from merger and accretion induced collapse of compact stellar objects, which may produce the cosmological gamma ray bursts (GRBs), are also very efficient and powerful cosmic ray accelerators. The expected luminosity, energy spectrum and chemical composition of cosmic rays from Galactic GRBs, most of which do not point in our direction, can explain the observed properties of Galactic cosmic rays.

Arnon Dar

1998-09-13T23:59:59.000Z

270

Afterglows as Diagnostics of Gamma Ray Burst Beaming  

E-Print Network (OSTI)

Abstract. If gamma ray bursts are highly collimated, radiating into only a small fraction of the sky, the energy requirements of each event may be reduced by several (up to 4–6) orders of magnitude, and the event rate increased correspondingly. The large Lorentz factors (?> ? 100) inferred from GRB spectra imply relativistic beaming of the gamma rays into an angle ? 1/?. We are at present ignorant of whether there are ejecta outside this narrow cone. Afterglows allow empirical tests of whether GRBs are well-collimated jets or spherical fireballs. The bulk Lorentz factor decreases and radiation is beamed into an ever increasing solid angle as the burst remnant expands. It follows that if gamma ray bursts are highly collimated, many more optical and radio transients should be observed without associated gamma rays than with them. In addition, a burst whose ejecta are beamed into angle ?m undergoes a qualitative change in evolution when ??m < ? 1: Before this, ? ? r?3/2, while afterwards, ? ? exp(?r/r ?

James E. Rhoads

1997-01-01T23:59:59.000Z

271

Constraints on relativity violations from gamma-ray bursts  

E-Print Network (OSTI)

Tiny violations of the Lorentz symmetry of relativity and the associated discrete CPT symmetry could emerge in a consistent theory of quantum gravity such as string theory. Recent evidence for linear polarization in gamma-ray bursts improves existing sensitivities to Lorentz and CPT violation involving photons by factors ranging from ten to a million.

Alan Kostelecky; Matthew Mewes

2013-01-23T23:59:59.000Z

272

Are there cosmological evolution of Gamma-Ray Bursts?  

E-Print Network (OSTI)

The variability of gamma-ray burst (GRB) is thought to be correlated with its absolute peak luminosity, and this relation had been used to derive an estimate of the redshifts of GRBs. Recently Amati et al. present the results of spectral and energetic properties of several GRBs with know redshifts. Here we analyse the properties of two group GRBs, one group with known redshift from afterglow observation, and another group with redshift derived from the luminosity- variability relation. We study the redshift dependence of various GRBs features in their cosmological rest frames, including the burst duration, the isotropic luminosity and radiated energy, and the peak energy Ep of ?F? spectra. We find that the properties of these two group GRBs are very similar, which strongly implies that the redshift derived from the luminosity-variability relation may be reliable. If this is true, then we see that the burst properties, such as their intrinsic duration, luminosity, radiated energy and peak energy Ep, are all correlated with the redshift, which means that the GRBs features are redshift dependent, i.e. there are cosmological evolution of gamma-ray bursts, and this can provide an interesting clue to the nature of GRBs. Furthermore we find that the Ep- L relation strongly supports the idea that gamma-ray burst emission comes from the internal shock. Key words: gamma rays: bursts

D. M. Wei

2008-01-01T23:59:59.000Z

273

Constraining axion by polarized prompt emission from gamma ray bursts  

E-Print Network (OSTI)

A polarized gamma ray emission spread over a sufficiently wide energy band from a strongly magnetized astrophysical object like gamma ray bursts (GRBs) offers an opportunity to test the hypothesis of invisible axion. The axionic induced dichroism of gamma rays at different energies should cause a misalignment of the polarization plane for higher energy events relative to that one for lower energies events resulting in the loss of statistics needed to form a pattern of the polarization signal to be recognized in a detector. According to this, any evidence of polarized gamma rays coming from an object with extended magnetic field could be interpreted as a constraint on the existence of the invisible axion for a certain parameter range. Based on reports of polarized MeV emission detected in several GRBs we derive a constraint on the axion-photon coupling. This constraint $\\g_{a\\gamma\\gamma}\\le 2.2\\cdot 10^{-11} {\\rm GeV^{-1}}$ calculated for the axion mass $m_a=10^{-3} {\\rm eV}$ is competitive with the sensitivity of CAST and becomes even stronger for lower masses.

A. Rubbia; A. S. Sakharov

2007-08-20T23:59:59.000Z

274

Plutonium Isotopic Measurements by Gamma-Ray Spectroscopy  

SciTech Connect

The nondestructive assay of plutonium is important as a safeguard tool in accounting for stategic nuclear material. Several nondestructive assay techniques, e.g., calorimetry and spontaneous fission assay detectors, require a knowledge of plutonium and americium isotopic ratios to convert their raw data to total grams of plutonium. This paper describes a nondestructive technique for calculating plutonium-238, plutonium-240, plutonium-241 and americium-241 relative to plutonium-239 from measured peak areas in the high resolution gamma-ray spectra of solid plutonium samples. Gamma-ray attenuation effects have been minimized by selecting sets of neighboring peaks in the spectrum whose components are due to the different isotopes. Since the detector efficiencies are approximately the same for adjacent peaks, the accuracy of the isotopic ratios are dependent on the half-lives, branching intensities and measured peak areas. The data presented describes the results obtained by analyzing gamma-ray spectra in the energy region from 120 to 700 keV. The majority of the data analyzed was obtained from plutonium material containing 6% plutonium-240. Sample weights varied from 0.25 g to approximately 1.2 kg. The methods have also been applied to plutonium samples containing up to 23% plutonium-240 with weights of 0.25 to 200g. Results obtained by gamma-ray spectroscopy are compared to chemical analyses of aliquots taken from the bulk samples.

Haas, Francis X.; Lemming, John F.

1976-05-01T23:59:59.000Z

275

Current Trends in Gamma Ray Detection for Radiological Emergency Response  

SciTech Connect

Passive and active detection of gamma rays from shielded radioactive materials, including special nuclear materials, is an important task for any radiological emergency response organization. This article reports on the current trends and status of gamma radiation detection objectives and measurement techniques as applied to nonproliferation and radiological emergencies.

Mukhopadhyay, S., Guss, P., Maurer, R.

2011-08-18T23:59:59.000Z

276

COMPACT BINARY PROGENITORS OF SHORT GAMMA-RAY BURSTS  

SciTech Connect

In recent years, detailed observations and accurate numerical simulations have provided support to the idea that mergers of compact binaries containing either two neutron stars (NSs) or an NS and a black hole (BH) may constitute the central engine of short gamma-ray bursts (SGRBs). The merger of such compact binaries is expected to lead to the production of a spinning BH surrounded by an accreting torus. Several mechanisms can extract energy from this system and power the SGRBs. Here we connect observations and numerical simulations of compact binary mergers, and use the current sample of SGRBs with measured energies to constrain the mass of their powering tori. By comparing the masses of the tori with the results of fully general-relativistic simulations, we are able to infer the properties of the binary progenitors that yield SGRBs. By assuming a constant efficiency in converting torus mass into jet energy, {epsilon}{sub jet} = 10%, we find that most of the tori have masses smaller than 0.01 M{sub Sun }, favoring 'high-mass' binary NSs mergers, i.e., binaries with total masses {approx}> 1.5 the maximum mass of an isolated NS. This has important consequences for the gravitational wave signals that may be detected in association with SGRBs, since 'high-mass' systems do not form a long-lived hypermassive NS after the merger. While NS-BH systems cannot be excluded to be the engine of at least some of the SGRBs, the BH would need to have an initial spin of {approx}0.9 or higher.

Giacomazzo, Bruno [JILA, University of Colorado and National Institute of Standards and Technology, Boulder, CO 80309 (United States); Perna, Rosalba [JILA and Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309 (United States); Rezzolla, Luciano [Max-Planck-Institut fuer Gravitationsphysik, Albert-Einstein-Institut, Potsdam D-14476 (Germany); Troja, Eleonora [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Lazzati, Davide [Department of Physics, NC State University, 2401 Stinson Drive, Raleigh, NC 27695-8202 (United States)

2013-01-10T23:59:59.000Z

277

Exploring the bizarrerie : research on selective physical processes in gamma-ray bursts.  

E-Print Network (OSTI)

??Gamma-ray bursts (GRBs) are the mysterious, short and intense flashes of gamma-rays in the space, and are believed to originate from the rare, explosively devastating,… (more)

Shen, Rongfeng

2010-01-01T23:59:59.000Z

278

High-energy emission and recent afterglow studies of gamma-ray bursts.  

E-Print Network (OSTI)

??Gamma-ray Bursts (GRBs) are powerful explosions that emit most of their energy, as their name suggests, in gamma-rays of typical energies of about 1 MeV.… (more)

Barniol Duran, Rodolfo Jose

2011-01-01T23:59:59.000Z

279

A Multi-wavelength study on gamma-ray bursts and their afterglows.  

E-Print Network (OSTI)

??During the prompt emission and afterglow phases, GRBs(Gamma-Ray Bursts) release their huge amount of energy not limited in gamma-ray, but in a wide range of… (more)

Zhang, Binbin

2011-01-01T23:59:59.000Z

280

Highlights of the Rome Workshop on Gamma-Ray Bursts in the Afterglow Era  

E-Print Network (OSTI)

I review some of the highlights of the Rome Workshop on Gamma-Ray Bursts, and discuss some of the questions these results pose about the nature and origin of gamma-ray bursts.

D. Q. Lamb

1999-09-01T23:59:59.000Z

Note: This page contains sample records for the topic "gamma-ray logging systems" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


281

Total-to-peak ratios of high purity germanium gamma ray detector  

E-Print Network (OSTI)

This study is concerned with the percentage of [gamma]-rays of a certain energy having their energy correctly measured by a high purity Germanium [gamma]-ray detector. The ratio between the total counts and the counts ...

Nelson, Justin Matthew, 1981-

2004-01-01T23:59:59.000Z

282

Relativistic Winds from Compact Gamma-Ray Sources: II. Pair Loading and Radiative Acceleration in Gamma-ray Bursts  

E-Print Network (OSTI)

We consider the effects of rapid pair creation by an intense pulse of gamma-rays propagating ahead of a relativistic shock. Side-scattered photons colliding with the main gamma-ray beam amplify the density of scattering charges. The acceleration rate of the pair-loaded medium is calculated, and its limiting bulk Lorentz factor related to the spectrum and compactness of the photon source. One obtains, as a result, a definite prediction for the relative inertia in baryons and pairs. The deceleration of a relativistic shock in the moving medium, and the resulting synchrotron emissivity, are compared with existing calculations for a static medium. The radiative efficiency is increased dramatically by pair loading. When the initial ambient density exceeds a critical value, the scattering depth traversed by the main gamma-ray pulse rises above unity, and the pulse is broadened. These considerations place significant constraints on burst progenitors: a pre-burst mass loss rate exceeding 10^{-5} M_\\odot per year is difficult to reconcile with individual pulses narrower than 10 s, unless the radiative efficiency is low. An anisotropic gamma-ray flux (on an angular scale \\Gamma^{-1} or larger) drives a large velocity shear that greatly increases the energy in the seed magnetic field forward of the propagating shock.

Christopher Thompson; Piero Madau

1999-09-06T23:59:59.000Z

283

A search for GeV-TeV emission from Gamma-ray Bursts using the Milagro detector  

E-Print Network (OSTI)

A search for GeV-TeV emission from Gamma-ray Bursts using the Milagro detector p. M. Saz Parkinson of operation. Keywords: gamma-ray sources; gamma-ray bursts; astronomical observations gamma-ray; gamma-ray telescope; Milagro PACS: 95.55.Ka; 95.85.Pw; 98.70.Rz INTRODUCTION Gamma-ray bursts (GRBs) were detected up

California at Santa Cruz, University of

284

Search for Short Duration Bursts of TeV Gamma Rays with the Milagrito Telescope  

E-Print Network (OSTI)

OG 2.3.07 Search for Short Duration Bursts of TeV Gamma Rays with the Milagrito Telescope Gus for short duration bursts of TeV photons. Such bursts may result from "traditional" gamma-ray bursts to gamma-ray bursts, the final stages of black hole evaporation) the most compelling reason may

California at Santa Cruz, University of

285

arXiv:astro-ph/0509571v119Sep2005 Gamma-Ray Burst Early Afterglows  

E-Print Network (OSTI)

arXiv:astro-ph/0509571v119Sep2005 Gamma-Ray Burst Early Afterglows Bing Zhang Department of Physics's Swift Gamma-Ray Burst Explorer open a new era for the multi-wavelength study of the very early afterglow phase of gamma-ray bursts (GRBs). GRB early afterglow information is essential to explore the unknown

Zhang, Bing

286

Explaining the light curves of Gamma-ray Bursts with precessing jets  

E-Print Network (OSTI)

A phenomenological model is presented to explain the light curves of gamma-ray bursts. Gamma-rays are produced in a narrow beam which sweeps through space due to the precession of a slaved accretion disc. The light curve expected from such a precessing luminosity cone can explain the complex temporal behavior of bright gamma-ray bursts.

Simon Portegies Zwart

1999-03-13T23:59:59.000Z

287

Six Years of Gamma Ray Burst Observations with BeppoSAX  

E-Print Network (OSTI)

I give a summary of the prompt X-/gamma-ray detections of Gamma Ray Bursts (GRBs) with the BeppoSAX satellite and discuss some significant results obtained from the study of the prompt emission of these GRBs obtained with the BeppoSAX Gamma Ray Burst Monitor and Wide Field Cameras.

Filippo Frontera

2004-07-30T23:59:59.000Z

288

Vol. 35 (2004) ACTA PHYSICA POLONICA B No 6--7 GAMMA RAY BURSTS #  

E-Print Network (OSTI)

multiwavelength survey of 63 Gamma Ray Bursts (GRBs) with unprecedented temporal coverage, we classify. Keywords: gamma-ray sources; gamma-ray bursts PACS: 98.70.Rz INTRODUCTION Using the network of three 2-m in our sample. Right panel : X-ray vs. optical flux (extrapolated at t=10 minutes after the burst event

Magiera, Andrzej

289

MilagroA TeV Observatory for Gamma Ray Bursts  

E-Print Network (OSTI)

The Biggest Bangs The Mystery of Gamma-Ray Bursts, The Most Violent Explosions in The Universe J. I. Did a Gamma-Ray Burst Kill the Dinosaurs? Will a Burst Kill Us? #15; Glossary #15; Sources #15; Index. On January 23, 1999, one of these four cameras recorded visible light from a gamma-ray burst

California at Santa Cruz, University of

290

The short gamma-ray burst SGR giant flare connection Kevin Hurley  

E-Print Network (OSTI)

SOLAR SUBMILLIMETER AND GAMMA-RAY BURST EMISSION P. Kaufmann,1,2 J.-P. Raulin,1 A. M. Melo,1 E headings: gamma rays: bursts -- Sun: flares 1. INTRODUCTION The interaction of ultrarelativistic electrons observations of a burst in the submillimeter and gamma-ray ranges were obtained for the first time on 2001

California at Berkeley, University of

291

Limits on Very High Energy Emission from Gamma-Ray Bursts with the Milagro  

E-Print Network (OSTI)

Limits on Very High Energy Emission from Gamma-Ray Bursts with the Milagro Observatory Miguel F of Milagro allow it to detect very high energy (VHE) gamma-ray burst emission with much higher sensitivity gamma-ray burst satellites at keV to MeV energies. Even in the absence of a positive detection, VHE

California at Santa Cruz, University of

292

1 Cactus Framework: Black Holes to Gamma Ray Bursts 7 Erik Schnetter1,2  

E-Print Network (OSTI)

Contents 1 Cactus Framework: Black Holes to Gamma Ray Bursts 7 Erik Schnetter1,2 , Christian D. Ott 94720, USA 1.1 Current challenges in relativistic astrophysics and the Gamma- Ray Burst problem-8493-0052-5/00/$0.00+$.50 c 2001 by CRC Press LLC 5 #12;#12;Chapter 1 Cactus Framework: Black Holes to Gamma Ray Bursts Erik

293

GAMMA-RAY BURSTS AND THE EARTH: EXPLORATION OF ATMOSPHERIC, BIOLOGICAL, CLIMATIC, AND BIOGEOCHEMICAL EFFECTS  

E-Print Network (OSTI)

GAMMA-RAY BURSTS AND THE EARTH: EXPLORATION OF ATMOSPHERIC, BIOLOGICAL, CLIMATIC Received 2005 May 19; accepted 2005 August 2 ABSTRACT Gamma-ray bursts (GRBs) are likely to have made extinction may have been initiated by a GRB. Subject headinggs: astrobiology -- gamma rays: bursts Online

Jackman, Charles H.

294

SOLAR SUBMILLIMETER AND GAMMA-RAY BURST EMISSION P. Kaufmann,1,2  

E-Print Network (OSTI)

SOLAR SUBMILLIMETER AND GAMMA-RAY BURST EMISSION P. Kaufmann,1,2 J.-P. Raulin,1 A. M. Melo,1 E headings: gamma rays: bursts -- Sun: flares 1. INTRODUCTION The interaction of ultrarelativistic electrons observations of a burst in the submillimeter and gamma-ray ranges were obtained for the first time on 2001

Giménez de Castro, Guillermo Carlos

295

UNIVERSITY of CALIFORNIA A SEARCH FOR TEV GAMMA-RAY BURST EMISSION WITH  

E-Print Network (OSTI)

UNIVERSITY of CALIFORNIA SANTA CRUZ A SEARCH FOR TEV GAMMA-RAY BURST EMISSION WITH THE MILAGRO of Figures vi List of Tables viii Abstract ix Dedication x Acknowledgments xi 1 Gamma-Ray Bursts 1 1 . . . . . . . . . . . . . . . . . . . . . . . . . . 76 5.6 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 6 Gamma-Ray Burst

California at Santa Cruz, University of

296

Climatic and biogeochemical effects of a galactic gamma ray burst Adrian L. Melott,1  

E-Print Network (OSTI)

Climatic and biogeochemical effects of a galactic gamma ray burst Adrian L. Melott,1 Brian C. Jackman (2005), Climatic and biogeochemical effects of a galactic gamma ray burst, Geophys. Res. Lett., 32, L14808, doi:10.1029/2005GL023073. 1. Terrestrial Implications of Gamma Ray Bursts in Our Galaxy [2

Jackman, Charles H.

297

arXiv:astro-ph/0611774v210Jan2007 Gamma-Ray Burst Afterglows  

E-Print Network (OSTI)

arXiv:astro-ph/0611774v210Jan2007 Gamma-Ray Burst Afterglows Bing Zhang Department of Physics in multi-wavelength are observed following Gamma-ray bursts (GRBs). Recent broad- band observational with the ambient medium. Key words: Gamma-Ray Bursts, Swift Observatory, X-rays, optical, radio 1. Introduction

Zhang, Bing

298

Studies of Gamma-Ray Burst Prompt Emission with RHESSI and NCT  

E-Print Network (OSTI)

4 RHESSI Tests of Quasi-Thermal Gamma-Ray Burst Spectral 4.1List of Tables ix Acknowledgments 1 Gamma-Ray Bursts 1.1 GRBx 2 RHESSI Gamma-Ray Burst Analysis Methods 2.1 The RHESSI

Bellm, Eric Christopher

2011-01-01T23:59:59.000Z

299

Search for Very High Energy Emission from Gamma-Ray Bursts using Milagro  

E-Print Network (OSTI)

Search for Very High Energy Emission from Gamma-Ray Bursts using Milagro P. M. Saz Parkinson 95064 Abstract. Gamma-Ray Bursts (GRBs) have been detected at GeV energies by EGRET and models predict for very high energy emission from a sample of 106 gamma-ray bursts (GRB) detected since the beginning

California at Santa Cruz, University of

300

Did a gamma-ray burst initiate the late Ordovician mass extinction?  

E-Print Network (OSTI)

Did a gamma-ray burst initiate the late Ordovician mass extinction? A.L. Melott1 , B.S. Lieberman2 Abstract: Gamma-ray bursts (GRBs) produce a flux of radiation detectable across the observable Universe words: Population and evolution, mass extinction, gamma-ray burst, Ordovician, ultraviolet ozone

Jackman, Charles H.

Note: This page contains sample records for the topic "gamma-ray logging systems" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


301

Gamma-Ray Bursts in the Swift Era N. Gehrels,1  

E-Print Network (OSTI)

1 Gamma-Ray Bursts in the Swift Era N. Gehrels,1 E. Ramirez-Ruiz,2 and D. B. Fox3 [1] NASA IS A GAMMA-RAY BURST? . . . . . . . . . . . . . . . . . . . . . . . . . 6 BURST AND AFTERGLOW OBSERVATIONS medium, high- redshift; gamma rays: observations, theory; stars: Wolf-Rayet; neutrinos; supernovae

Rodriguez, Luis F.

302

The Interplanetary Network Supplement to the BATSE 5B Catalog of Cosmic Gamma-Ray Bursts  

E-Print Network (OSTI)

The Interplanetary Network Supplement to the BATSE 5B Catalog of Cosmic Gamma-Ray Bursts K. Hurley Interplanetary Network (IPN) localization information for 343 gamma-ray bursts observed by the Burst Gamma-Ray Observatory (CGRO) mission, obtained by analyzing the arrival times of these bursts

California at Berkeley, University of

303

Search for gravitational waves associated with the InterPlanetary Network short gamma ray bursts  

E-Print Network (OSTI)

Search for gravitational waves associated with the InterPlanetary Network short gamma ray bursts V with short gamma ray bursts detected by the InterPlanetary Network (IPN) during LIGO's fifth science run and Virgo's first science run. The IPN localisation of short gamma ray bursts is limited to extended error

California at Berkeley, University of

304

THE INTERPLANETARY NETWORK SUPPLEMENT TO THE BATSE CATALOGS OF UNTRIGGERED COSMIC GAMMA-RAY BURSTS  

E-Print Network (OSTI)

THE INTERPLANETARY NETWORK SUPPLEMENT TO THE BATSE CATALOGS OF UNTRIGGERED COSMIC GAMMA-RAY BURSTS gamma-ray bursts (GRBs) observed as untriggered events by the Burst and Transient Source Experiment to detect BATSE un- triggered bursts. Subject headinggs: catalogs -- gamma rays: bursts Online material

California at Berkeley, University of

305

Search for very high energy gamma-rays from WIMP annihilations near the Sun with the Milagro Detector  

E-Print Network (OSTI)

The neutralino, the lightest stable supersymmetric particle, is a strong theoretical candidate for the missing astronomical ``dark matter''. A profusion of such neutralinos can accumulate near the Sun when they lose energy upon scattering and are gravitationally captured. Pair-annihilations of those neutralinos may produce very high energy (VHE, above $100 GeV$) gamma-rays. Milagro is an air shower array which uses the water Cherenkov technique to detect extensive air showers and is capable of observing VHE gamma-rays from the direction of the Sun with an angular resolution of $0.75^{\\circ}$. Analysis of Milagro data with an exposure to the Sun of 1165 hours presents the first attempt to detect TeV gamma-rays produced by annihilating neutralinos captured by the Solar system and shows no statistically significant signal. Resulting limits that can be set on gamma-ray flux due to near-Solar neutralino annihilations and on neutralino cross-section are presented.

Milagro Collaboration

2004-05-14T23:59:59.000Z

306

NMIS with Imaging and Gamma Ray Spectrometry for Pu, HEU, HE and Other Materials  

SciTech Connect

The Nuclear Material Identification System (NMIS) has been under development at ORNL and the National Nuclear Security Administration (NNSA) Y-12 National Security Complex since 1984. In the mid-1990s, what is now the US Department of Energy (DOE) Office of Nuclear Verification (ONV) realized that it was a useful technology for future arms control treaty applications and supported further development of the system. In 2004, fast-neutron imaging was incorporated into the system. In 2007, the ONV decided to develop a fieldable version of the system, designated as FNMIS, for potential use in future treaties. The FNMIS is being developed to be compatible with the eventual incorporation of gamma-ray spectrometry and an information barrier. This report addresses how and what attributes could be determined by the FNMIS system with gamma-ray spectrometry. The NMIS is a time-dependent coincidence system that incorporates tomographic imaging (including mapping of the fission sites) and gamma-ray spectrometry. It utilizes a small, lightweight (30 lb), portable deuterium-tritium (DT) neutron (14.1 MeV) generator (4 x 10{sup 7} neutrons/second) for active interrogation and can also perform passive interrogation. A high-purity germanium (HPGe) gamma-ray detector with multichannel analysis can be utilized in conjunction with the source for active interrogation or passively. The system uses proton recoil scintillators: 32 small 2.5 x 2.5 x 10.2-cm-thick plastic scintillators for imaging and at least two 2 x 2 arrays of 27 x 27 x 10-cm-thick plastic scintillators that detect induced fission radiation. The DT generator contains an alpha detector that time and directionally tags a fan beam of some of the neutrons emitted and subdivides it into pixels. A fast (1 GHz) time correlation processor measures the time-dependent coincidence among all detectors in the system. A computer-controlled scanner moves the small detectors and the source appropriately for scanning a target object for imaging. The system is based on detection of transmitted 14.1 MeV neutrons, fission neutrons, and gamma rays from spontaneous, inherent source fission of the target, fission neutrons and gamma rays induced by the external DT source, gamma rays from natural emissions of uranium and plutonium, and induced gamma-ray emission by the interaction of the 14.1 MeV neutrons from the DT source. The NMIS can and has been used with a time-tagged californium spontaneous fission source. It has also been used with pulsed interrogation sources such as LINACs, DT, and deuterium-deuterium (DD) sources. This system is uniquely suited for detection of shielded highly enriched uranium (HEU), plutonium, and other special nuclear materials and detection of high explosives (HE) and chemical agents. The NMIS will be adapted to utilize a trusted processor that incorporates information barrier and authentication techniques using open software and then be useful in some international applications for materials whose characteristics may be classified. The proposed information barrier version of the NMIS system would consist of detectors and cables, the red (classified side) computer system, which processes the data, and the black (unclassified side) computer, which handles the computer interface. The system could use the 'IB wrapper' concept proposed by Los Alamos National Laboratory and the software integrity (digital signatures) system proposed by Sandia. Since it is based entirely on commercially available components, the entire system, including NMIS data acquisition boards, can be built with commercial off-the-shelf components. This system is being developed into a fieldable system (FNMIS) for potential arms control treaties by the ONV. The system will be modularly constructed with the RF shielded modules connected to the processor by appropriate control and signal cable in metal conduit. The FNMIS is presently being designed for eventual incorporation of gamma-ray spectrometry and an information barrier to protect classified information. The system hardware and software can be configu

Mihalczo, John T [ORNL; Mullens, James Allen [ORNL

2012-03-01T23:59:59.000Z

307

Extrapolations of BATSE Gamma-Ray Burst Spectra to the Optical-UV Band  

E-Print Network (OSTI)

Many gamma-ray burst counterpart searches are being conducted in the optical-UV band. To both predict detectability and understand the meaning of any detections or upper limits, we extrapolate gamma-ray spectra from 54 bright gamma-ray bursts to optical-UV energies. We assume optical emission is concurrent with gamma-ray emission and do not consider quiescent or fading counterparts. We find that the spectrum must be steeper (greater flux at low energy) than a simple extrapolation of the gamma-ray spectrum for more than one simultaneous optical flash to be observable per year by current searches.

Lyle Ford; David Band

1996-07-10T23:59:59.000Z

308

Gamma-ray bursts, axion emission and string theory dilaton  

E-Print Network (OSTI)

The emission of axions from supernovae is an interesting possibility to account for the Gamma-Ray Bursts provided their energy can be effectively converted into electromagnetic energy elsewhere. The connection between supernova and gamma-ray bursts has been recently confirmed by the observed correlation between the burst of April 25, 1998 and the supernova SN1998bw. We argue that the axion convertion into photons can be more efficient if one considers the coupling between an intermediate scale axion and the string theory dilaton along with the inclusion of string loops. We also discuss the way dilaton dynamics may allow for a more effective energy exchange with electromagnetic radiation in the expansion process of fireballs.

O. Bertolami

1999-01-14T23:59:59.000Z

309

Neutron and Gamma Ray Pulse Shape Discrimination with Polyvinyltoluene  

SciTech Connect

The goal of this was research effort was to test the ability of two poly vinyltoluene research samples to produce recordable, distinguishable signals in response to gamma rays and neutrons. Pulse shape discrimination was performed to identify if the signal was generated by a gamma ray or a neutron. A standard figure of merit for pulse shape discrimination was used to quantify the gamma-neutron pulse separation. Measurements were made with gamma and neutron sources with and without shielding. The best figure of merit obtained was 1.77; this figure of merit was achieved with the first sample in response to an un-moderated 252Cf source shielded with 5.08 cm of lead.

Lintereur, Azaree T.; Ely, James H.; Stave, Jean A.; McDonald, Benjamin S.

2012-03-01T23:59:59.000Z

310

Color Superconductivity in Compact Stars and Gamma Ray Bursts  

E-Print Network (OSTI)

We study the effects of color superconductivity on the structure and formation of compact stars. We show that it is possible to satisfy most of recent observational boundaries on masses and radii if a diquark condensate forms in a hybrid or a quark star. Moreover, we find that a huge amount of energy, of the order of $10^{53}$ erg, can be released in the conversion from a (metastable) hadronic star into a (stable) hybrid or quark star, if the presence of a color superconducting phase is taken into account. Accordingly to the scenario proposed in Astrophys.J.586(2003)1250, the energy released in this conversion can power a Gamma Ray Burst. This mechanism can explain the recent observations indicating a delay, of the order of days or years, between a few Supernova explosions and the subsequent Gamma Ray Burst.

A. Drago; A. Lavagno; G. Pagliara

2003-04-08T23:59:59.000Z

311

Fiber fed x-ray/gamma ray imaging apparatus  

SciTech Connect

X-ray/gamma ray imaging apparatus is disclosed for detecting the position, energy, and intensity of x-ray/gamma ray radiation comprising scintillation means disposed in the path of such radiation and capable of generating photons in response to such radiation; first photodetection means optically bonded to the scintillation means and capable of generating an electrical signal indicative of the intensity, and energy of the radiation detected by the scintillation means; second photodetection means capable of generating an electrical signal indicative of the position of the radiation in the radiation pattern; and means for optically coupling the scintillation means to the second photodetection means. The photodetection means are electrically connected to control and storage means which may also be used to screen out noise by rejecting a signal from one photodetection means not synchronized to a signal from the other photodetection means; and also to screen out signals from scattered radiation.

Hailey, Charles J. (San Francisco, CA); Ziock, Klaus-Peter (Livermore, CA)

1992-01-01T23:59:59.000Z

312

Quark Stars as inner engines for Gamma Ray Bursts?  

E-Print Network (OSTI)

A model for Gamma ray bursts inner engine based on quark stars (speculated to exist in nature) is presented. We describe how and why these objects might constitute new candidates for GRB inner engines. At the heart of the model is the onset of exotic phases of quark matter at the surface of such stars, in particular the 2-flavor color superconductivity. A novel feature of such a phase is the generation of particles which are unstable to photon decay providing a natural mechanism for a fireball generation; an approach which is fundamentally different from models where the fireball is generated during collapse or conversion of neutron star to quark star processes. The model is capable of reproducing crucial features of Gamma ray bursts, such as the episodic activity of the engine (multiple and random shell emission) and the two distinct categories of the bursts (two regimes are isolated in the model with \\sim 2 s and \\sim 81 s burst total duration).

R. Ouyed; F. Sannino

2001-03-01T23:59:59.000Z

313

Photospheric signatures imprinted on the gamma-ray burst spectra  

E-Print Network (OSTI)

A solution is presented for the spectrum of high-energy gamma-ray burst photons confined to a quasi-thermal baryonic photosphere. The solution is valid in the steady-state limit assuming the region under consideration is optically thick to the continuously injected photons. It is shown that for a high luminosity photosphere, the non-thermal electrons resulting from gamma-ray Compton cooling lose their energy by upscattering the soft thermalised radiation. The resulting spectral modifications offer the possibility of diagnosing not only the burst comoving luminosity but also the baryon load of the ejecta. This model leads to a simple physical interpretation of X-ray rich bursts and anomalous low-energy slopes.

Enrico Ramirez-Ruiz

2005-09-08T23:59:59.000Z

314

Power Density Spectra of Gamma-Ray Bursts  

E-Print Network (OSTI)

Power density spectra (PDSs) of long gamma-ray bursts provide useful information on GRBs, indicating their self-similar temporal structure. The best power-law PDSs are displayed by the longest bursts (T_90 > 100 s) in which the range of self-similar time scales covers more than 2 decades. Shorter bursts have apparent PDS slopes more strongly affected by statistical fluctuations. The underlying power law can then be reproduced with high accuracy by averaging the PDSs for a large sample of bursts. This power-law has a slope alpha\\approx -5/3 and a sharp break at 1 Hz. The power-law PDS provides a new sensitive tool for studies of gamma-ray bursts. In particular, we calculate the PDSs of bright bursts in separate energy channels. The PDS flattens in the hard channel (h\

Andrei M. Beloborodov

1999-11-08T23:59:59.000Z

315

Gamma-ray Emission from Crushed Clouds in Supernova Remnants  

E-Print Network (OSTI)

It is shown that the radio and gamma-ray emission observed from newly-found "GeV-bright" supernova remnants (SNRs) can be explained by a model, in which a shocked cloud and shock-accelerated cosmic rays (CRs) frozen in it are simultaneously compressed by the supernova blastwave as a result of formation of a radiative cloud shock. Simple reacceleration of pre-existing CRs is generally sufficient to power the observed gamma-ray emission through the decays of neutral pions produced in hadronic interactions between high-energy protons (nuclei) and gas in the compressed-cloud layer. This model provides a natural account of the observed synchrotron radiation in SNRs W51C, W44 and IC 443 with flat radio spectral index, which can be ascribed to a combination of secondary and reaccelerated electrons and positrons.

Uchiyama, Yasunobu; Funk, Stefan; Tajima, Hiroyasu; Tanaka, Takaaki

2010-01-01T23:59:59.000Z

316

Stochastic wake field particle acceleration in Gamma-Ray Bursts  

E-Print Network (OSTI)

Gamma-Ray Burst (GRB) prompt emission can, for specific conditions, be so powerful and short-pulsed to strongly influence any surrounding plasma. In this paper, we briefly discuss the possibility that a very intense initial burst of radiation produced by GRBs satisfy the intensity and temporal conditions to cause stochastic wake-field particle acceleration in a surrounding plasma of moderate density. Recent laboratory experiments clearly indicate that powerful laser beam pulses of tens of femtosecond duration hitting on target plasmas cause efficient particle acceleration and betatron radiation up to tens of MeV. We consider a simple but realistic GRB model for which particle wake-field acceleration can first be excited by a very strong low-energy precursor, and then be effective in producing the observed prompt X-ray and gamma-ray GRB emission. We also briefly discuss some of the consequences of this novel GRB emission mechanism.

G. Barbiellini; F. Longo; N. Omodei; A. Celotti; M. Tavani

2006-04-11T23:59:59.000Z

317

Gamma-Rays from Radio Galaxies: Fermi-Lat Observations  

E-Print Network (OSTI)

We review the high energy properties of Misaligned AGNs associated with gamma-ray sources detected by Fermi in 24 months of survey. Most of them are nearby emission low power radio galaxies (i.e FRIs) which probably have structured jets. On the contrary, high power radio sources (i.e FRIIs) with GeV emission are rare. The small number of FRIIs does not seem to be related to their higher redshifts. Assuming proportionality between the radio core flux and the gamma-ray flux, several of them are expected to be bright enough to be detected above 100 MeV in spite of their distance. We suggest that beaming/jet structural differences are responsible for the detection rate discrepancy observed between FRIs and FRIIs.

Grandi, Paola

2011-01-01T23:59:59.000Z

318

Detecting special nuclear materials in containers using high-energy gamma rays emitted by fission products  

DOE Patents (OSTI)

A method and a system for detecting the presence of special nuclear materials in a container. The system and its method include irradiating the container with an energetic beam, so as to induce a fission in the special nuclear materials, detecting the gamma rays that are emitted from the fission products formed by the fission, to produce a detector signal, comparing the detector signal with a threshold value to form a comparison, and detecting the presence of the special nuclear materials using the comparison.

Norman, Eric B. (Oakland, CA); Prussin, Stanley G. (Kensington, CA)

2007-10-02T23:59:59.000Z

319

High energy particles from gamma-ray bursts  

E-Print Network (OSTI)

A review is presented of the fireball model of gamma-ray bursts (GRBs), and of the production in GRB fireballs of high energy protons and neutrinos. Constraints imposed on the model by recent afterglow observations, which support the association of GRB and ultra-high energy cosmic-ray (UHECR) sources, are discussed. Predictions of the GRB model for UHECR production, which can be tested with planned large area UHECR detectors and with planned high energy neutrino telescopes, are reviewed.

Eli Waxman

2001-03-13T23:59:59.000Z

320

Dark gamma-ray bursts: possible role of multiphoton processes  

E-Print Network (OSTI)

The absence of optical afterglow at some gamma-ray bursts (so called dark bursts) requires analyses of physical features of this phenomenon. It is shown that such singularity can be connected with multiphoton processes of frequencies summation in the Rayleigh- Jeans part of spectra, their pumping into higher frequencies. It can be registered most probably on young objects with still thin plasma coating, without further thermalization, i.e. soon after a prompt beginning of the explosive activity.

Mark E. Perel'man

2009-07-27T23:59:59.000Z

Note: This page contains sample records for the topic "gamma-ray logging systems" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


321

Radiation from Poynting Flux Acceleration and Gamma-Ray Bursts  

E-Print Network (OSTI)

We compute the radiation output of electrons accelerated by Poynting flux numerically from Particle-In-Cell simulations, and derive an analytic formula to explain these numerical results. We show that the in-situ power output and critical frequency are much below those predicted by the classical synchrotron formulae. We then apply these results to a model of long gamma-ray bursts. This model predicts spectral break energies remarkably consistent with the observed values.

Liang, Edison

2007-01-01T23:59:59.000Z

322

Gamma-Ray Burst Detection with INTEGRAL/SPI  

E-Print Network (OSTI)

The spectrometer SPI, one of the two main instruments of the INTEGRAL spacecraft, has strong capabilities in the field of Gamma-Ray Burst (GRB) detections. In its 16 deg field of view (FoV) SPI is able to trigger and to localize GRBs with an accuracy for strong bursts better than 1 deg. The expected GRB detection rate is about one per month.

Andreas von Kienlin; Nikolas Arend; Giselher Lichti; Andrew Strong; Paul Connell

2004-07-05T23:59:59.000Z

323

Search for neutrinos from Gamma-Ray Bursts with ANTARES  

E-Print Network (OSTI)

A method to search for neutrino induced showers from gamma-ray bursts in the ANTARES detector is presented. ANTARES consists of a three-dimensional array of photosensitive devices that measure Cherenkov light induced by charged particles produced by high energy neutrinos interacting in the detector vicinity. The shower channel is complementary to the more commonly used upgoing muon channel. The corresponding detection volume is smaller, but has the advantage of being sensitive to neutrinos of any flavour.

Eleonora Presani

2011-04-20T23:59:59.000Z

324

The Gamma Ray Burst Rate at High Photon Energies  

E-Print Network (OSTI)

Some gamma-ray burst (GRB) spectra exhibit high energy tails with the highest photon energy detected at 18 GeV. The spectral slope of the high-energy tails is sufficiently flat in nu F_nu to consider the possibility of their detection at still higher energies. We calculate how many bursts can reasonably be expected above a given energy threshold for a cosmological distribution of bursts satisfying the observed apparent brightness distribution. The crucial point is that the gamma-ray absorption by pair production in the intergalactic diffuse radiation field eliminates bursts from beyond the gamma-ray horizon tau ~ 1, thus drastically reducing the number of bursts at high energies. Our results are consistent with the non-detection of bursts by current experiments in the 100 GeV to 100 TeV energy range. For the earth-bound detector array MILAGRO, we predict a maximal GRB rate of ~ 10 events per year. The Whipple Observatory can detect, under favorable conditions, ~1 event per year. The event rate for the HEGRA array is ~ 0.01 per year. Detection of significantly higher rates of bursts would severely challenge cosmological burst scenarios.

Karl Mannheim; Dieter Hartmann; Burkhardt Funk

1996-05-17T23:59:59.000Z

325

Gamma-Ray Bursts Above 1 GeV  

E-Print Network (OSTI)

One of the principal results obtained by the Compton Gamma Ray Observatory relating to the study of gamma-ray bursts was the detection by the EGRET instrument of energetic ($>$100 MeV) photons from a handful of bright bursts. The most extreme of these was the single 18 GeV photon from the GRB940217 source. Given EGRET's sensitivity and limited field of view, the detection rate implies that such high energy emission may be ubiquitous in bursts. Hence expectations that bursts emit out to at least TeV energies are quite realistic, and the associated target-of-opportunity activity of the TeV gamma-ray community is well-founded. This review summarizes the observations and a handful of theoretical models for generating GeV--TeV emission in bursts sources, outlining possible ways that future positive detections could discriminate between different scenarios. The power of observations in the GeV--TeV range to distinguish between spectral structure intrinsic to bursts and that due to the intervening medium between source and observer is also discussed.

Matthew G. Baring

1997-11-21T23:59:59.000Z

326

GAMMA-RAY BURSTS FROM NEUTRON STAR BINARIES  

E-Print Network (OSTI)

We report on general relativistic hydrodynamic studies which indicate several new physical processes which may contribute to powering gamma-ray bursts in neutron star binaries. Relativistically driven compression, heating, and collapse of the individual stars can occur many seconds before inspiral and merger. This compression may produce a neutrino burst of ? 10 53 ergs lasting several seconds. The associated thermal neutrino emission produces an e + ? e ? pair plasma by ?¯? annihilation. We show first results of a simulated burst which produces ? 10 51 erg in ?-rays. We also discuss a preliminary study of the evolution of the magnetic field lines attached to the fluid as the stars orbit. We show that the relativistically driven fluid motion might lead to the formation of extremely strong magnetic fields ( ? 10 17 gauss) in and around the stars which could affect to the formation and evolution of a gamma-ray burst. It has been speculated for some time that inspiraling neutron stars could provide a power source for cosmological gamma-ray bursts. The rate of neutron star mergers (when integrated over the number of galaxies out to high redshift) could account for the observed GRB event rate. The possibility that at least some ?-ray bursts involve

G. J. Mathews

1997-01-01T23:59:59.000Z

327

Gamma-Ray Lines from Radiative Dark Matter Decay  

E-Print Network (OSTI)

The decay of dark matter particles which are coupled predominantly to charged leptons has been proposed as a possible origin of excess high-energy positrons and electrons observed by cosmic-ray telescopes PAMELA and Fermi LAT. Even though the dark matter itself is electrically neutral, the tree-level decay of dark matter into charged lepton pairs will generically induce radiative two-body decays of dark matter at the quantum level. Using an effective theory of leptophilic dark matter decay, we calculate the rates of radiative two-body decays for scalar and fermionic dark matter particles. Due to the absence of astrophysical sources of monochromatic gamma rays, the observation of a line in the diffuse gamma-ray spectrum would constitute a strong indication of a particle physics origin of these photons. We estimate the intensity of the gamma-ray line that may be present in the energy range of a few TeV if the dark matter decay interpretation of the leptonic cosmic-ray anomalies is correct and comment on observational prospects of present and future Imaging Cherenkov Telescopes, in particular the CTA.

Mathias Garny; Alejandro Ibarra; David Tran; Christoph Weniger

2010-11-16T23:59:59.000Z

328

Gamma ray astrophysics, the extragalactic background light, and new physics  

Science Conference Proceedings (OSTI)

Very high energy gamma-rays are expected to be absorbed by the extragalactic background light over cosmological distances via the process of electron-positron pair production. However, recent observations of cosmologically distant emitters by ground based gamma-ray telescopes might be indicative of a higher-than-expected degree of transparency of the universe. One mechanism to explain this observation is the oscillation between photons and axion-like-particles (ALPs). Here we explore this possibility, focusing on photon-ALP conversion in the magnetic fields in and round gamma-ray sources and in the magnetic field of the Milky Way, where some fraction of the ALP flux is converted back into photons. We show that this mechanism can be efficient in allowed regions of the ALP parameter space, as well as in typical configurations of the Galactic Magnetic Field. As case example, we consider the spectrum observed from a HESS source. We also discuss features of this scenario which could be used to distinguish it from standard or other exotic models.

Serpico, Pasquale D.; /Fermilab

2008-09-01T23:59:59.000Z

329

Are we observing Lorentz violation in gamma ray bursts?  

E-Print Network (OSTI)

From recent observations of gamma-ray bursts (GRBs), it appears that spectral time lags between higher-energy gamma rays photons and lower-energy photons vary with energy difference and time (distance) traveled. These lags appear to be smaller for the most luminous (close) bursts but larger for the fainter (farther away) bursts. From this observation, it has been suggested that it might be possible to determine the distance (L) these bursts have traveled from these time lags alone, without performing any red-shift measurements. These observed spreads (dispersion) of high-energy electromagnetic pulses of different energies with time contradict the special theory of relativity (STR). However, extended theories (ET) of the STR have been developed that contain a dispersive term, predicting the above observations. An example of such an ET is presented, allowing us to derive a relationship between time lags of gamma rays of different energies and distance L traveled from their origin. In addition, this theory predicts the origin of X-ray flashes.

Theodore G. Pavlopoulos

2005-08-12T23:59:59.000Z

330

Log Summarization and Anomaly Detection for TroubleshootingDistributed Systems  

SciTech Connect

Today's system monitoring tools are capable of detectingsystem failures such as host failures, OS errors, and network partitionsin near-real time. Unfortunately, the same cannot yet be said of theend-to-end distributed softwarestack. Any given action, for example,reliably transferring a directory of files, can involve a wide range ofcomplex and interrelated actions across multiple pieces of software:checking user certificates and permissions, getting details for allfiles, performing third-party transfers, understanding re-try policydecisions, etc. We present an infrastructure for troubleshooting complexmiddleware, a general purpose technique for configurable logsummarization, and an anomaly detection technique that works in near-realtime on running Grid middleware. We present results gathered using thisinfrastructure from instrumented Grid middleware and applications runningon the Emulab testbed. From these results, we analyze the effectivenessof several algorithms at accurately detecting a variety of performanceanomalies.

Gunter, Dan; Tierney, Brian L.; Brown, Aaron; Swany, Martin; Bresnahan, John; Schopf, Jennifer M.

2007-08-01T23:59:59.000Z

331

ON THE RECENTLY DISCOVERED CORRELATIONS BETWEEN GAMMA-RAY AND X-RAY PROPERTIES OF GAMMA-RAY BURSTS  

SciTech Connect

Recently, many correlations between the prompt {gamma}-ray emission properties and the X-ray afterglow properties of gamma-ray bursts (GRBs) have been inferred from a comprehensive analysis of the X-ray light curves of more than 650 GRBs measured with the Swift X-Ray Telescope (Swift/XRT) during the years 2004-2010. We show that these correlations are predicted by the cannonball (CB) model of GRBs. They result from the dependence of GRB observables on the bulk motion Lorentz factor and viewing angle of the jet of highly relativistic plasmoids (CBs) that produces the observed radiations by interaction with the medium through which it propagates. Moreover, despite their different physical origins, long GRBs (LGRBs) and short-hard bursts (SHBs) in the CB model share similar kinematic correlations, which can be combined into triple correlations satisfied by both LGRBs and SHBs.

Dado, Shlomo; Dar, Arnon [Physics Department, Technion, Haifa 32000 (Israel)

2013-09-20T23:59:59.000Z

332

The high-energy gamma-ray light curve of PSR B1259 -63  

E-Print Network (OSTI)

The high-energy gamma-ray light curve of the binary system PSR B1259 -63, is computed using the approach that successfully predicted the spectrum at periastron. The simultaneous INTEGRAL and H.E.S.S. spectra taken 16 days after periastron currently permit both a model with dominant radiative losses, high pulsar wind Lorentz factor and modest efficiency as well as one with dominant adiabatic losses, a slower wind and higher efficiency. In this paper we shown how the long-term light curve may help to lift this degeneracy.

J. G. Kirk; Lewis Ball; S. Johnston

2005-09-30T23:59:59.000Z

333

The Synergy of Gamma-Ray Burst Detectors in the GLAST Era  

E-Print Network (OSTI)

Simultaneous observations by the large number of gamma-ray burst detectors operating in the GLAST era will provide the spectra, lightcurves and locations necessary for studying burst physics and testing the putative relations between intrinsic burst properties. The detectors' energy band and the accumulation timescale of their trigger system affect their sensitivity to hard vs. soft and long vs. short bursts. Coordination of the Swift and GLAST observing plans consistent with Swift's other science objectives could increase the detection rate of GLAST bursts with redshifts.

David Band; for the GLAST collaboration

2008-01-31T23:59:59.000Z

334

Gamma Ray Burst triggering Supernova Explosion (and other effects on neighbouring stars)  

E-Print Network (OSTI)

The initial burst of a gamma ray burst (GRB) is usually followed by a longer-lived afterglow emitted at longer wavelengths. The evidence for a physical connection between GRBs and core collapse supernovae (SN) has increased since the discovery of GRB afterglows. So far SN signatures have been found in only a few GRBs. Here we propose the possibility of a GRB triggering the collapse of a WR or RG star in a binary system producing a SN, and typical signatures. We also look at the effects of GRBs on MS and WD stars in the neighbourhood. The possibility of GRBs retarding star formation in an interstellar cloud is also discussed.

C. Sivaram; Kenath Arun

2010-09-28T23:59:59.000Z

335

Ultra-high energy cosmic rays, cascade gamma-rays, and high-energy neutrinos from gamma-ray bursts  

E-Print Network (OSTI)

Gamma-ray bursts (GRBs) are sources of energetic, highly variable fluxes of gamma rays, which demonstrates that they are powerful particle accelerators. Besides relativistic electrons, GRBs should also accelerate high-energy hadrons, some of which could escape cooling to produce ultra-high energy cosmic rays (UHECRs). Acceleration of high-energy hadrons in GRB blast waves will be established if high-energy neutrinos produced through photopion interactions in the blast wave are detected from GRBs. Limitations on the energy in nonthermal hadrons and the number of expected neutrinos are imposed by the fluxes from pair-photon cascades initiated in the same processes that produce neutrinos. Only the most powerful bursts at fluence levels >~ 3e-4 erg/cm^2 offer a realistic prospect for detection of >> TeV neutrinos. Detection of high-energy neutrinos is likely if GRB blast waves have large baryon loads and Doppler factors <~ 200. Cascade gamma rays will accompany neutrino production and might already have been detected as anomalous emission components in the spectra of some GRBs. Prospects for detection of GRBs in the Milky Way are also considered.

Charles D. Dermer; Armen Atoyan

2006-06-26T23:59:59.000Z

336

GRB 050117: SIMULTANEOUS GAMMA-RAY AND X-RAY OBSERVATIONS WITH THE SWIFT SATELLITE Joanne E. Hill,1, 2  

E-Print Network (OSTI)

The Swift Gamma-Ray Burst Explorer performed its first autonomous, X-ray follow-up to a newly detected GRB from the XRT position. Subject headingg: gamma rays: bursts 1. INTRODUCTION The Swift Gamma-ray Burst Explorer (Gehrels et al. 2004) was launched on 2004 November 20 to study gamma-ray bursts (GRBs) over

Zhang, Bing

337

Definition: Gamma Log | Open Energy Information  

Open Energy Info (EERE)

Definition Definition Edit with form History Facebook icon Twitter icon » Definition: Gamma Log Jump to: navigation, search Dictionary.png Gamma Log Gamma logging is a method of measuring naturally occurring gamma radiation to characterize the rock or sediment in a borehole or drill hole. It is a wireline logging method used in mining, mineral exploration, water-well drilling, for formation evaluation in oil and gas well drilling and for other related purposes. Different types of rock emit different amounts and different spectra of natural gamma radiation.[1] View on Wikipedia Wikipedia Definition Gamma ray logging is a method of measuring naturally occurring gamma radiation to characterize the rock or sediment in a borehole or drill hole. It is a wireline logging method used in mining, mineral exploration,

338

The Dawn of Nuclear Photonics with Laser-based Gamma-rays  

Science Conference Proceedings (OSTI)

A renaissance in nuclear physics is occurring around the world because of a new kind of incredibly bright, gamma-ray light source that can be created with short pulse lasers and energetic electron beams. These highly Mono-Energetic Gamma-ray (MEGa-ray) sources produce narrow, laser-like beams of incoherent, tunable gamma-rays and are enabling access and manipulation of the nucleus of the atom with photons or so called 'Nuclear Photonics'. Just as in the early days of the laser when photon manipulation of the valence electron structure of the atom became possible and enabling to new applications and science, nuclear photonics with laser-based gamma-ray sources promises both to open up wide areas of practical isotope-related, materials applications and to enable new discovery-class nuclear science. In the United States, the development of high brightness and high flux MEGa-ray sources is being actively pursued at the Lawrence Livermore National Laboratory in Livermore (LLNL), California near San Francisco. The LLNL work aims to create by 2013 a machine that will advance the state of the art with respect to source the peak brightness by 6 orders of magnitude. This machine will create beams of 1 to 2.3 MeV photons with color purity matching that of common lasers. In Europe a similar but higher photon energy gamma source has been included as part of the core capability that will be established at the Extreme Light Infrastructure Nuclear Physics (ELI-NP) facility in Magurele, Romania outside of Bucharest. This machine is expected to have an end point gamma energy in the range of 13 MeV. The machine will be co-located with two world-class, 10 Petawatt laser systems thus allowing combined intense-laser and gamma-ray interaction experiments. Such capability will be unique in the world. In this talk, Dr. Chris Barty from LLNL will review the state of the art with respect to MEGa-ray source design, construction and experiments and will describe both the ongoing projects around the world as well some of the exciting applications that these machines will enable. The optimized interaction of short-duration, pulsed lasers with relativistic electron beams (inverse laser-Compton scattering) is the key to unrivaled MeV-scale photon source monochromaticity, pulse brightness and flux. In the MeV spectral range, such Mono-Energetic Gamma-ray (MEGa-ray) sources can have many orders of magnitude higher peak brilliance than even the world's largest synchrotrons. They can efficiently perturb and excite the isotope-specific resonant structure of the nucleus in a manner similar to resonant laser excitation of the valence electron structure of the atom.

Barty, C J

2011-03-17T23:59:59.000Z

339

The Large Area Telescope on the Fermi Gamma-ray Space Telescope Mission  

SciTech Connect

The Large Area Telescope (Fermi/LAT, hereafter LAT), the primary instrument on the Fermi Gamma-ray Space Telescope (Fermi) mission, is an imaging, wide field-of-view (FoV), high-energy {gamma}-ray telescope, covering the energy range from below 20 MeV to more than 300 GeV. The LAT was built by an international collaboration with contributions from space agencies, high-energy particle physics institutes, and universities in France, Italy, Japan, Sweden, and the United States. This paper describes the LAT, its preflight expected performance, and summarizes the key science objectives that will be addressed. On-orbit performance will be presented in detail in a subsequent paper. The LAT is a pair-conversion telescope with a precision tracker and calorimeter, each consisting of a 4 x 4 array of 16 modules, a segmented anticoincidence detector that covers the tracker array, and a programmable trigger and data acquisition system. Each tracker module has a vertical stack of 18 (x, y) tracking planes, including two layers (x and y) of single-sided silicon strip detectors and high-Z converter material (tungsten) per tray. Every calorimeter module has 96 CsI(Tl) crystals, arranged in an eight-layer hodoscopic configuration with a total depth of 8.6 radiation lengths, giving both longitudinal and transverse information about the energy deposition pattern. The calorimeter's depth and segmentation enable the high-energy reach of the LAT and contribute significantly to background rejection. The aspect ratio of the tracker (height/width) is 0.4, allowing a large FoV (2.4 sr) and ensuring that most pair-conversion showers initiated in the tracker will pass into the calorimeter for energy measurement. Data obtained with the LAT are intended to (1) permit rapid notification of high-energy {gamma}-ray bursts and transients and facilitate monitoring of variable sources, (2) yield an extensive catalog of several thousand high-energy sources obtained from an all-sky survey, (3) measure spectra from 20 MeV to more than 50 GeV for several hundred sources, (4) localize point sources to 0.3-2 arcmin, (5) map and obtain spectra of extended sources such as SNRs, molecular clouds, and nearby galaxies, (6) measure the diffuse isotropic {gamma}-ray background up to TeV energies, and (7) explore the discovery space for dark matter.

Atwood, W.B.; /UC, Santa Cruz; Abdo, Aous A.; /Naval Research Lab, Wash., D.C.; Ackermann, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Anderson, B. /UC, Santa Cruz; Axelsson, M.; /Stockholm U.; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Band, D.L.; /NASA, Goddard /NASA, Goddard; Barbiellini, Guido; /INFN, Trieste /Trieste U.; Bartelt, J.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bastieri, Denis; /INFN, Padua /Padua U.; Baughman, B.M.; /Ohio State U.; Bechtol, K.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bederede, D.; /DAPNIA, Saclay; Bellardi, F.; /INFN, Pisa; Bellazzini, R.; /INFN, Pisa; Berenji, B.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bignami, G.F.; /Pavia U.; Bisello, D.; /INFN, Padua /Padua U.; Bissaldi, E.; /Garching, Max Planck Inst., MPE; Blandford, R.D.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /INFN, Perugia /Perugia U. /NASA, Goddard /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /INFN, Pisa /INFN, Pisa /Bari U. /INFN, Bari /Ecole Polytechnique /Washington U., Seattle /INFN, Padua /Padua U. /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /IASF, Milan /IASF, Milan /Kalmar U. /Royal Inst. Tech., Stockholm /DAPNIA, Saclay /ASI, Rome /INFN, Pisa /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /George Mason U. /Naval Research Lab, Wash., D.C. /NASA, Goddard /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /DAPNIA, Saclay /NASA, Goddard /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Montpellier U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; /more authors..

2009-05-15T23:59:59.000Z

340

Log Summarization  

NLE Websites -- All DOE Office Websites (Extended Search)

Log Log Summarization and Anomaly Detection for Troubleshooting Distributed Systems Dan Gunter #1 , Brian L. Tierney #2 , Aaron Brown ∗3 , Martin Swany ∗4 , John Bresnahan !5 , Jennifer M. Schopf !6 # Lawrence Berkeley National Laboratory, Berkeley, CA, USA 1 dkgunter@lbl.gov 2 bltierney@lbl.gov ∗ University of Delaware, Newark, DE, USA 3 brown@cis.udel.edu 4 swany@cis.udel.edu ! Argonne National Laboratory, Argonne, IL, USA 5 bresnaha@mcs.anl.gov 6 jms@mcs.anl.gov Abstract- Today's system monitoring tools are capable of detecting system failures such as host failures, OS errors, and network partitions in near-real time. Unfortunately, the same cannot yet be said of the end-to-end distributed software stack. Any given action, for example, reliably transferring a directory of files, can involve a wide range of complex and interrelated actions across multiple pieces

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341

On the sensitivity of the HAWC observatory to gamma-ray bursts  

E-Print Network (OSTI)

We present the sensitivity of HAWC to Gamma Ray Bursts (GRBs). HAWC is a very high-energy gamma-ray observatory currently under construction in Mexico at an altitude of 4100 m. It will observe atmospheric air showers via the water Cherenkov method. HAWC will consist of 300 large water tanks instrumented with 4 photomultipliers each. HAWC has two data acquisition (DAQ) systems. The main DAQ system reads out coincident signals in the tanks and reconstructs the direction and energy of individual atmospheric showers. The scaler DAQ counts the hits in each photomultiplier tube (PMT) in the detector and searches for a statistical excess over the noise of all PMTs. We show that HAWC has a realistic opportunity to observe the high-energy power law components of GRBs that extend at least up to 30 GeV, as it has been observed by Fermi LAT. The two DAQ systems have an energy threshold that is low enough to observe events similar to GRB 090510 and GRB 090902b with the characteristics observed by Fermi LAT. HAWC will prov...

Abeysekara, A U; Aguilar, S; Alfaro, R; Almaraz, E; Álvarez, C; Álvarez-Romero, J de D; Álvarez, M; Arceo, R; Arteaga-Velázquez, J C; Badillo, C; Barber, A; Baughman, B M; Bautista-Elivar, N; Belmont, E; Benítez, E; BenZvi, S Y; Berley, D; Bernal, A; Bonamente, E; Braun, J; Caballero-Lopez, R; Cabrera, I; Carramiñana, A; Carrasco, L; Castillo, M; Chambers, L; Conde, R; Condreay, P; Cotti, U; Cotzomi, J; D'Olivo, J C; de la Fuente, E; De León, C; Delay, S; Delepine, D; DeYoung, T; Diaz, L; Diaz-Cruz, L; Dingus, B L; Duvernois, M A; Edmunds, D; Ellsworth, R W; Fick, B; Fiorino, D W; Flandes, A; Fraija, N I; Galindo, A; García-Luna, J L; García-Torales, G; Garfias, F; González, L X; González, M M; Goodman, J A; Grabski, V; Gussert, M; Guzmán-Ceron, C; Hampel-Arias, Z; Harris, T; Hays, E; Hernandez-Cervantes, L; Hüntemeyer, P H; Imran, A; Iriarte, A; Jimenez, J J; Karn, P; Kelley-Hoskins, N; Kieda, D; Langarica, R; Lara, A; Lauer, R; Lee, W H; Linares, E C; Linnemann, J T; Longo, M; Luna-García, R; Martínez, H; Martínez, J; Martínez, L A; Martínez, O; Martínez-Castro, J; Martos, M; Matthews, J; McEnery, J E; Medina-Tanco, G; Mendoza-Torres, J E; Miranda-Romagnoli, P A; Montaruli, T; Moreno, E; Mostafa, M; Napsuciale, M; Nava, J; Nellen, L; Newbold, M; Noriega-Papaqui, R; Oceguera-Becerra, T; Tapia, A Olmos; Orozco, V; Pérez, V; Pérez-Pérez, E G; Perkins, J S; Pretz, J; Ramirez, C; Ramírez, I; Rebello, D; Rentería, A; Reyes, J; Rosa-González, D; Rosado, A; Ryan, J M; Sacahui, J R; Salazar, H; Salesa, F; Sandoval, A; Santos, E; Schneider, M; Shoup, A; Silich, S; Sinnis, G; Smith, A J; Sparks, K; Springer, W; Suárez, F; Suarez, N; Taboada, I; Tellez, A F; Tenorio-Tagle, G; Tepe, A; Toale, P A; Tollefson, K; Torres, I; Ukwatta, T N; Valdes-Galicia, J; Vanegas, P; Vasileiou, V; Vázquez, O; Vázquez, X; Villaseñor, L; Wall, W; Walters, J S; Warner, D; Westerhoff, S; Wisher, I G; Wood, J; Yodh, G B; Zaborov, D; Zepeda, A

2011-01-01T23:59:59.000Z

342

Joint anisotropy and source count constraints on the contribution of blazars to the diffuse gamma-ray background  

E-Print Network (OSTI)

We place new constraints on the contribution of blazars to the large-scale isotropic gamma-ray background (IGRB) by jointly analyzing the measured source count distribution (logN-logS) of blazars and the measured intensity and anisotropy of the IGRB. We find that these measurements point to a consistent scenario in which unresolved blazars make less than 20% of the IGRB intensity at 1-10 GeV while accounting for the majority of the measured anisotropy in that energy band. These results indicate that the remaining fraction of the IGRB intensity is made by a component with a low level of intrinsic anisotropy. We determine upper limits on the anisotropy from non-blazar sources, adopting the best-fit parameters of the measured source count distribution to calculate the unresolved blazar anisotropy. In addition, we show that the anisotropy measurement excludes some recently proposed models of the unresolved blazar population.

Alessandro Cuoco; Eiichiro Komatsu; Jennifer Siegal-Gaskins

2012-02-23T23:59:59.000Z

343

Gamma-ray Bursts Produced by Mirror Stars  

E-Print Network (OSTI)

I argue that cosmic Gamma-ray Bursts (GRB) may be produced by collapses or mergers of stars made of `mirror' matter. The mirror neutrinos (which are sterile for our matter) produced at these events can oscillate into ordinary neutrinos. The annihilations or decays of the latter create an electron-positron plasma and subsequent relativistic fireball with a very low baryon load needed for GRBs. The concept of mirror matter is able to explain several key problems of modern astrophysics: neutrino anomalies, the missing mass, MACHO microlensing events and GRBs. Thus this concept becomes very appealing and should be considered quite seriously and attentively.

S. Blinnikov

1999-02-21T23:59:59.000Z

344

Gamma-Ray Bursts and Dark Matter - a joint origin?  

E-Print Network (OSTI)

A scenario is presented where large quark-gluon plasma (QGP) objects escaping the quark-hadron transition in the early Universe account for the baryonic dark matter as well as act as the sources for gamma-ray bursts. Two basic assumptions are made. Firstly, we assume that a QGP consisting of u,d and s quarks is the absolute ground state of QCD and secondly, that the quark-hadron transition in the early Universe was of first order. Both particle physics and astrophysics constraints are discussed, mainly from an observational point of view.

Daniel Enstrom

1998-10-13T23:59:59.000Z

345

Gamma-ray bursts and the sociology of science  

E-Print Network (OSTI)

I discuss what we have learned about Gamma-Ray Bursts (GRBs) by studying their `afterglows', and how these are interpreted in the generally-accepted `fireball' model of GRBs, as well as in the generally-unaccepted `cannonball' model of the same phenomena. The interpretation of GRBs is a good example around which to frame a discussion of the different approaches to science found in various fields, such as high-energy physics (HEP), high-energy astrophysics, or even the deciphering of ancient languages. I use this example to draw conclusions on `post-academic' science, and on the current status of European HEP.

A. De Rujula

2003-06-16T23:59:59.000Z

346

Gamma-Ray Bursts and Quantum Cosmic Censorship  

E-Print Network (OSTI)

Gamma-ray bursts are believed to result from the coalescence of binary neutron stars. However, the standard proposals for conversion of the gravitational energy to thermal energy have difficulties. We show that if the merger of the two neutron stars results in a naked singularity, instead of a black hole, the ensuing quantum particle creation can provide the requisite thermal energy in a straightforward way. The back-reaction of the created particles can avoid the formation of the naked singularity predicted by the classical theory. Hence cosmic censorship holds in the quantum theory, even if it were to be violated in classical general relativity.

T. P. Singh

1998-05-17T23:59:59.000Z

347

Can Sequentially Linked Gamma-Ray Bursts Nullify Randomness?  

E-Print Network (OSTI)

In order to nullify the property of randomness perceived in the dispersion of gamma-ray bursts (GRB's) we introduce two new procedures. 1. Create a segmented group of sequentially linked GRB's and quantify the resultant angles. 2. Create segmented groups of sequentially linked GRB's in order to identify the location of GRB's that are positioned at equidistance, by using the selected GRB as the origin for a paired point circle, where the circumference of said circle intercepts the location of other GRB's in the same group.

Charles Fleischer

2012-05-02T23:59:59.000Z

348

High Energy Neutrinos from Cosmological Gamma-Ray Burst Fireballs  

E-Print Network (OSTI)

Observations suggest that $\\gamma$-ray bursts (GRBs) are produced by the dissipation of the kinetic energy of a relativistic fireball. We show that a large fraction, $\\ge 10%$, of the fireball energy is expected to be converted by photo-meson production to a burst of $\\sim10^{14} eV$ neutrinos. A km^2 neutrino detector would observe at least several tens of events per year correlated with GRBs, and test for neutrino properties (e.g. flavor oscillations, for which upward moving $\\tau$'s would be a unique signature, and coupling to gravity) with an accuracy many orders of magnitude better than is currently possible.

Eli Waxman; John Bahcall

1997-01-30T23:59:59.000Z

349

Gamma-Ray Bursts from Primordial Quark Objects in Space  

E-Print Network (OSTI)

We investigate the possibility that gamma-ray bursts originate in a concentric spherical shell with a given average redshift and find that this is indeed compatible with the data from the third BATSE (3B) catalog. It is also shown that there is enough freedom in the choice of unknown burst properties to allow even for extremely large distances to the majority of bursts. Therefore, we speculate about an early, and very energetic, origin of bursts, and suggest that they come from phase transitions in massive objects of pure quark matter, left over from the Big Bang.

B. Anoushirvani; D. Enström; S. Fredriksson; J. Hansson; P. Ökvist; A. Nicolaidis; S. Ekelin

1997-11-28T23:59:59.000Z

350

KINEMATIC ORIGIN OF CORRELATIONS BETWEEN GAMMA-RAY BURST OBSERVABLES  

Science Conference Proceedings (OSTI)

Recently, several new correlations between gamma-ray burst (GRB) observables have been discovered. Like previously well-established correlations, they challenge GRB models. Here, we show that in the cannonball (CB) model of GRBs, the newly discovered correlations have the same simple kinematic origin as those discovered earlier. They all result from the strong dependence of the observed radiations on the Lorentz and Doppler factors of the jet of highly relativistic plasmoids (CBs) that produces the observed radiations by interaction with the medium through which it propagates.

Dado, Shlomo; Dar, Arnon, E-mail: dado@phep3.technion.ac.il, E-mail: arnon@physics.technion.ac.il [Physics Department, Technion, Haifa 32000 (Israel)

2012-04-20T23:59:59.000Z

351

Ultra high energy neutrinos from gamma ray bursts  

E-Print Network (OSTI)

Protons accelerated to high energies in the relativistic shocks that generate gamma ray bursts photoproduce pions, and then neutrinos in situ. I show that ultra high energy neutrinos (> 10^19 eV) are produced during the burst and the afterglow. A larger flux, also from bursts, is generated via photoproduction off CMBR photons in flight but is not correlated with currently observable bursts, appearing as a bright background. Adiabatic/synchrotron losses from protons/pions/muons are negligible. Temporal and directional coincidences with bursts detected by satellites can separate correlated neutrinos from the background.

Mario Vietri

1998-02-18T23:59:59.000Z

352

Luminosities and Space Densities of Short Gamma-Ray Bursts  

E-Print Network (OSTI)

Using the Euclidean value of as a cosmological distance indicator, we derive the isotropic-equivalent characteristic peak luminosity of gamma-ray bursts both longer and shorter than 2 s. The short bursts have essentially the same characteristic peak luminosity of 0.6 x 10^51 erg (0.064s)^-1 as do the long bursts. This may apply also to bursts with durations less than 0.25 s. The local space density of short bursts is around three times lower than that of long bursts.

Maarten Schmidt

2001-08-29T23:59:59.000Z

353

INTERPLANETARY NETWORK LOCALIZATIONS OF KONUS SHORT GAMMA-RAY BURSTS  

SciTech Connect

Between the launch of the Global Geospace Science Wind spacecraft in 1994 November and the end of 2010, the Konus-Wind experiment detected 296 short-duration gamma-ray bursts (including 23 bursts which can be classified as short bursts with extended emission). During this period, the Interplanetary Network (IPN) consisted of up to 11 spacecraft, and using triangulation, the localizations of 271 bursts were obtained. We present the most comprehensive IPN localization data on these events. The short burst detection rate, {approx}18 yr{sup -1}, exceeds that of many individual experiments.

Pal'shin, V. D.; Svinkin, D. S.; Aptekar, R. L.; Golenetskii, S. V.; Frederiks, D. D.; Mazets, E. P.; Oleynik, P. P.; Ulanov, M. V. [Ioffe Physical Technical Institute, St. Petersburg, 194021 (Russian Federation); Hurley, K. [Space Sciences Laboratory, University of California, 7 Gauss Way, Berkeley, CA 94720-7450 (United States); Cline, T.; Trombka, J.; McClanahan, T. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Mitrofanov, I. G.; Golovin, D. V.; Kozyrev, A. S.; Litvak, M. L.; Sanin, A. B. [Space Research Institute, 84/32, Profsoyuznaya, Moscow 117997 (Russian Federation); Boynton, W.; Fellows, C.; Harshman, K., E-mail: val@mail.ioffe.ru [Department of Planetary Sciences, University of Arizona, Tucson, AZ 85721 (United States); and others

2013-08-15T23:59:59.000Z

354

Gamma-Ray Bursts and Dark Energy - Dark Matter interaction  

E-Print Network (OSTI)

In this work Gamma Ray Burst (GRB) data is used to place constraints on a putative coupling between dark energy and dark matter. Type Ia supernovae (SNe Ia) constraints from the Sloan Digital Sky Survey II (SDSS-II) first-year results, the cosmic microwave background radiation (CMBR) shift parameter from WMAP seven year results and the baryon acoustic oscillation (BAO) peak from the Sloan Digital Sky Survey (SDSS) are also discussed. The prospects for the field are assessed, as more GRB events become available.

T. Barreiro; O. Bertolami; P. Torres

2010-04-26T23:59:59.000Z

355

Are Durations of Weak Gamma-Ray Bursts Reliable?  

E-Print Network (OSTI)

Simulations in the GUSBAD Catalog of gamma-ray bursts suggest that the apparent duration of a burst decreases as its amplitude is decreased. We see no evidence for this effect in the BATSE catalog. We show that for a burst at the detection limit, the typical signal-to-noise ratio at the edges of the T90 duration is around 1.5, suggesting that T90 must be quite uncertain. The situation for T50 is less unfavorable. Simulations using the exact procedure to derive the durations in the BATSE catalog would be useful in quantifying the effect.

Maarten Schmidt

2005-08-16T23:59:59.000Z

356

Gamma ray burst distances and the timescape cosmology  

E-Print Network (OSTI)

Gamma ray bursts can potentially be used as distance indicators, providing the possibility of extending the Hubble diagram to redshifts ~7. Here we follow the analysis of Schaefer (2007), with the aim of distinguishing the timescape cosmological model from the \\LambdaCDM model by means of the additional leverage provided by GRBs in the range 2 < z < 7. We find that the timescape model fits the GRB sample slightly better than the \\LambdaCDM model, but that the systematic uncertainties are still too little understood to distinguish the models.

Peter R. Smale

2011-07-27T23:59:59.000Z

357

GeV Emission from Collisional Magnetized Gamma Ray Bursts  

E-Print Network (OSTI)

Magnetic fields may play a dominant role in gamma-ray bursts, and recent observations by the Fermi satellite indicate that GeV radiation, when detected, arrives delayed by seconds from the onset of the MeV component. Motivated by this, we discuss a magnetically dominated jet model where both magnetic dissipation and nuclear collisions are important. We show that, for parameters typical of the observed bursts, such a model involving a realistic jet structure can reproduce the general features of the MeV and a separate GeV radiation component, including the time delay between the two. The model also predicts a multi-GeV neutrino component.

P. Mészáros; M. J. Rees

2011-04-26T23:59:59.000Z

358

Automatic Quenching of High Energy gamma-ray Sources by Synchrotron Photons  

Science Conference Proceedings (OSTI)

Here we investigate evolution of a magnetized system, in which continuously produced high energy emission undergoes annihilation on a soft photon field, such that the synchrotron radiation of the created electron-positron pairs increases number density of the soft photons. This situation is important in high energy astrophysics, because, for an extremely wide range of magnetic field strengths (nano to mega Gauss), it involves {gamma}-ray photons with energies between 0.3GeV and 30TeV. We derive and analyze the conditions for which the system is unstable to runaway production of soft photons and ultrarelativistic electrons, and for which it can reach a steady state with an optical depth to photon-photon annihilation larger than unity, as well those for which efficient pair loading of the emitting volume takes place. We also discuss the application of our analysis to a realistic situation involving astrophysical sources of a broad-band {gamma}-ray emission and briefly consider the particular case of sources close to active supermassive black holes.

Stawarz, Lukasz; /KIPAC, Menlo Park /SLAC /Jagiellonian U., Astron. Observ.; Kirk, John; /Heidelberg, Max Planck Inst.

2007-02-02T23:59:59.000Z

359

Michael Logli  

Science Conference Proceedings (OSTI)

Michael is a science writer, generating content for Inform magazine and the Oil Mill Gazetteer. Michael Logli Contact Information contact contact us Michael Logli S

360

Brief Studying of Oil Crust Thickness Measurement by Gamma Ray Compton Scattering Approach  

E-Print Network (OSTI)

The relation between the scattering cross section and the scattering angle under different energy condition of the incident rays is analyzed. From Compton scattering total cross section, a formula of quasi-parallel incident gamma ray Compton scattering response function versus to thickness of oil crust target is derived and analyzed. Numerical fitting result shows that there exists cubic relation between response function of gamma ray and thickness of oil crust. Key words: Gamma ray, Compton scattering, oil crust

Mamatrishat, Mamat; Jie, Ding; Shiheng, Wang

2008-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "gamma-ray logging systems" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


361

Milagro Search for Very High Energy Emission from Gamma-Ray Bursts in the Swift Era  

E-Print Network (OSTI)

2005. 1. Me´sza´ros, P. & Rees, M. Optical and long-wavelength afterglow from gamma- ray bursts model. Astrophys. J. 517, L109­-L112 (1999). 3. Ford, L. A. et al. BATSE observations of gamma-ray burst, F. et al. Spectral properties of the prompt X-ray emission and afterglow from the gamma-ray burst

California at Santa Cruz, University of

362

Once again on the duration of nuclear gamma-ray-emission and gamma-ray-absorption processes  

SciTech Connect

In addition to previous indications of a long-term character of the processes of gamma-ray emission and absorption by nuclei, another two simple arguments in support of this picture are presented. It is shown that the Fourier integral for a short wave train is a frequency distribution whose width is many orders of magnitude larger than actual intrinsic widths of gamma lines. The uncertainty in the photon spatial position is found to be about {tau}c, which is the length of the wave train emitted by a nucleus over the average lifetime {tau} of this nucleus in an excited state.

Davydov, A. V., E-mail: andrey.davydov@itep.ru [Institute of Theoretical and Experimental Physics (Russian Federation)

2011-01-15T23:59:59.000Z

363

Studies of Gamma-Ray Burst Prompt Emission with RHESSI and NCT.  

E-Print Network (OSTI)

??Gamma-Ray Bursts (GRBs) are the most luminous objects in the universe. They herald a catastrophic energy release which manifests itself in tenths to hundreds of… (more)

Bellm, Eric Christopher

2011-01-01T23:59:59.000Z

364

Gamma-Ray Burst Afterglows as probes of their host galaxies and the Cosmos.  

E-Print Network (OSTI)

??Gamma-ray Bursts (GRBs) represent the sole class of catastrophic phenomena seen over almost the entire history of the Universe. Their extreme luminosities in high energy… (more)

Cucchiara, Antonino

2010-01-01T23:59:59.000Z

365

Gamma-ray bursts and their afterglows: toward a unified model.  

E-Print Network (OSTI)

??Although much progress has been made in our understanding of gamma-ray bursts (GRBs) and their afterglows in the last few decades, some critical questions remain… (more)

McMahon, Erin Malia, 1980-

2008-01-01T23:59:59.000Z

366

Swift Pointing and the Association Between Gamma-Ray Bursts and Gravitational-Wave Bursts  

E-Print Network (OSTI)

The currently accepted model for gamma-ray burst phenomena involves the violent formation of a rapidly rotating solar mass black hole. Gravitational waves should be associated with the black-hole formation, and their detection would permit this model to be tested, the black hole progenitor (e.g., coalescing binary or collapsing stellar core) identified, and the origin of the gamma rays (within the expanding relativistic fireball or at the point of impact on the interstellar medium) located. Even upper limits on the gravitational-wave strength associated with gamma-ray bursts could constrain the gamma-ray burst model. To do any of these requires joint observations of gamma-ray burst events with gravitational and gamma-ray detectors. Here we examine how the quality of an upper limit on the gravitational-wave strength associated with gamma-ray burst observations depends on the relative orientation of the gamma-ray-burst and gravitational-wave detectors, and apply our results to the particular case of the Swift Burst-Alert Telescope (BAT) and the LIGO gravitational-wave detectors. A result of this investigation is a science-based ``figure of merit'' that can be used, together with other mission constraints, to optimize the pointing of the Swift telescope for the detection of gravitational waves associated with gamma-ray bursts.

Lee Samuel Finn; Badri Krishnan; Patrick J. Sutton

2003-04-11T23:59:59.000Z

367

Are Short and Long Gamma Ray Bursts Really of Different Origin?  

E-Print Network (OSTI)

It is shown that short and long gamma ray bursts (GRBs) are of the same origin and, furthermore, correlated with their duration.

Ernst Karl Kunst

2000-12-06T23:59:59.000Z

368

An Attempt To Use Aerial Gamma-Ray Spectrometry Results In Petrochemic...  

Open Energy Info (EERE)

are fairly rich in radioelement concentrations. The aerial gamma-ray spectrometric survey data, gathered for the purpose of radioactive mineral exploration were utilized as an...

369

Can precessing jets explain the light curves of Gamma-ray Bursts?  

E-Print Network (OSTI)

We present a phenomenological model to explain the light curves of gamma-ray bursts. In the model a black hole is orbited by a precessing accretion disc which is fed by a neutron star. Gamma-rays are produced in a highly collimated beam via the Blandford-Znajek mechanism. The gamma-ray beam sweeps through space due to the precession of the slaved accretion disc. The light curve expected from such a precessing luminosity cone can explain the complex temporal behavior of observed bright gamma-ray bursts.

Simon Portegies Zwart; Chang-Hwan Lee; Hyun Kyu Lee

1998-08-19T23:59:59.000Z

370

Testing and Improving the Luminosity Relations for Gamma-Ray Bursts.  

E-Print Network (OSTI)

??Gamma Ray Bursts (GRBs) have several luminosity relations where a measurable property of a burst light curve or spectrum is correlated with the burst luminosity.… (more)

Collazzi, Andrew

2011-01-01T23:59:59.000Z

371

The investigation of intrinsic spectral and temporal properties of gamma-ray bursts .  

E-Print Network (OSTI)

??Gamma-ray bursts (GRBs) have become a truly unique puzzle in Astronomy. Unlike quasars and pulsars which were explained within years of their discovery, the origins… (more)

[No author

2005-01-01T23:59:59.000Z

372

Fission prompt gamma-ray multiplicity distribution measurements and simulations at DANCE  

SciTech Connect

The nearly energy independence of the DANCE efficiency and multiplicity response to {gamma} rays makes it possible to measure the prompt {gamma}-ray multiplicity distribution in fission. We demonstrate this unique capability of DANCE through the comparison of {gamma}-ray energy and multiplicity distribution between the measurement and numerical simulation for three radioactive sources {sup 22}Na, {sup 60}Co, and {sup 88}Y. The prospect for measuring the {gamma}-ray multiplicity distribution for both spontaneous and neutron-induced fission is discussed.

Chyzh, A; Wu, C Y; Ullmann, J; Jandel, M; Bredeweg, T; Couture, A; Norman, E

2010-08-24T23:59:59.000Z

373

The Sample of Gamma-ray Bursts Observed With SPI-ACS  

E-Print Network (OSTI)

The SPI anticoincidence shield consists of 91 BGO crystals and is operated as a nearly omnidirectional gamma-ray burst detector above ~75 keV. Since the start of the mission 269 gamma-ray burst candidates have been detected. 110 bursts have been confirmed with the instruments included in the 3rd Interplanetary Network. Here we present a preliminary statistical analysis of the SPI-ACS sample of gamma-ray bursts and gamma-ray burst candidates; in particular we discuss the duration distribution of the bursts. A prominent population of short burst candidates (duration ray nuclei interacting in the detectors.

A. Rau; A. von Kienlin; K. Hurley; G. G. Lichti

2004-05-06T23:59:59.000Z

374

A Cautionary Note on Gamma Ray Burst Nearest Neighbor Statistics  

E-Print Network (OSTI)

In this letter we explore the suggestion of Quashnock and Lamb (1993) that nearest neighbor correlations among gamma ray burst positions indicate the possibility of burst repetitions within various burst sub-classes. With the aid of Monte Carlo calculations we compare the observed nearest neighbor distributions with those expected from an isotropic source population weighted by the published BATSE exposure map. The significance of the results are assessed via the Kolmogorov-Smirnov (K-S) test, as well as by a comparison to Monte Carlo simulations. The K-S results are in basic agreement with those of Quashnock and Lamb. However, as Narayan and Piran (1993) point out, and the Monte Carlo calculations confirm, the K-S test overestimates the significance of the observed distributions. We compare the sensitivity of these results to both the definitions of the assumed burst sub-classes and the burst positional errors. Of the two, the positional errors are more significant and indicate that the results of Quashnock and Lamb may be due to systematic errors, rather than any intrinsic correlation among the burst positions. Monte Carlo simulations also show that with the current systematic errors, the nearest neighbor statistic is not very sensitive to moderate repetition rates. Until the BATSE statistical and systematic errors are fully understood, the burst nearest neighbor correlations cannot be claimed to be significant evidence for burst repetitions. Subject Headings: gamma rays: bursts — methods: statistical

Michael A. Nowak

1993-01-01T23:59:59.000Z

375

On the Bimodal Distribution of Gamma-Ray Bursts  

E-Print Network (OSTI)

Kouveliotou et al. (1993) recently confirmed that gamma-ray bursts are bimodal in duration. In this paper we compute the statistical properties of the short ($\\le 2$~s) and long ($>2$~s) bursts using a method of analysis that makes no assumption regarding the location of the bursts, whether in the Galaxy or at a cosmological distance. We find the 64 ms channel on BATSE to be more sensitive to short bursts and the 1024 ms channel is more sensitive to long bursts. We show that all the currently available data are consistent with the simple hypothesis that both short and long bursts have the same spatial distribution and that within each population the sources are standard candles. The rate of short bursts is $\\sim 0.4$ of the rate of long bursts. Although the durations of short and long gamma-ray bursts span several orders of magnitude and the total energy of a typical short burst is smaller than that of a typical long burst by a factor of $\\sim 20$, surprisingly the peak luminosities of the two kinds of bursts are equal to within a factor of $\\sim 2$.

Shude Mao; Ramesh Narayan; Tsvi Piran

1993-04-16T23:59:59.000Z

376

Swift 1644+57: The Longest Gamma-ray Burst?  

E-Print Network (OSTI)

Swift recently discovered an unusual gamma-ray and x-ray transient (Sw 1644+57) that was initially identified as a long-duration gamma-ray burst (GRB). However, the ~ 10 keV x-ray emission has persisted for over a month with a luminosity comparable to its peak value. The astrometric coincidence of the source with the center of its host galaxy, together with other considerations, motivated the interpretation that Sw 1644+57 was produced by an outburst from a 10^{6-7} M_sun black hole at the center of the galaxy. Here we consider the alternate possibility that Sw 1644+57 is indeed a long-duration GRB, albeit a particularly long one. We discuss the general properties of very long-duration, low-power GRB-like transients associated with the core-collapse of a massive star. Both neutron star (magnetar) spindown and black hole accretion can power such events. The requirements for producing low-power, very long-duration GRBs by magnetar spindown are similar to those for powering extremely luminous supernovae by magne...

Quataert, Eliot

2011-01-01T23:59:59.000Z

377

Neutrino Emission from Gamma-Ray Burst Fireballs, Revised  

E-Print Network (OSTI)

We review the neutrino flux from gamma-ray bursts, which is estimated from gamma-ray observations and used for the interpretation of recent IceCube data, from a particle physics perspective. We numerically calculate the neutrino flux for the same astrophysical assumptions as the analytical fireball neutrino model, including the dominant pion and kaon production modes, flavor mixing, and magnetic field effects on the secondary muons, pions, and kaons. We demonstrate that taking into account the full energy dependencies of all spectra, the normalization of the expected neutrino flux reduces by about one order of magnitude and the spectrum shifts to higher energies, where we can pin down the exact origin of the discrepancies by the re-computation of the analytical models. We also reproduce the IceCube-40 analysis for exactly the same bursts and same assumptions and illustrate the impact of uncertainties. We conclude that the baryonic loading of the fireballs, which is an important control parameter for the emission of cosmic rays, can be constrained significantly with the full-scale experiment after about ten years.

Svenja Hümmer; Philipp Baerwald; Walter Winter

2011-12-05T23:59:59.000Z

378

Nuclear Equation of State from Observations of Short Gamma-Ray Burst Remnants  

E-Print Network (OSTI)

The favoured progenitor model for short $\\gamma$-ray bursts (SGRBs) is the merger of two neutron stars that triggers an explosion with a burst of collimated $\\gamma$-rays. Following the initial prompt emission, some SGRBs exhibit a plateau phase in their $X$-ray light curves that indicates additional energy injection from a central engine, believed to be a rapidly rotating, highly magnetised neutron star. The collapse of this `protomagnetar' to a black hole is likely to be responsible for a steep decay in $X$-ray flux observed at the end of the plateau. In this letter, we show that these observations can be used to effectively constrain the equation of state of dense matter. In particular, we show that the known distribution of masses in binary neutron star systems, together with fits to the $X$-ray light curves, provide constraints that exclude the softest and stiffest plausible equations of state. We further illustrate how a future gravitational wave observation with Advanced LIGO/Virgo can place tight constraints on the equation of state, by adding into the picture a measurement of the chirp mass of the SGRB progenitor.

Paul D. Lasky; Brynmor Haskell; Vikram Ravi; Eric J. Howell; David M. Coward

2013-11-06T23:59:59.000Z

379

Baseline drift effect on the performance of neutron and gamma ray discrimination using frequency gradient analysis  

E-Print Network (OSTI)

Frequency gradient analysis (FGA) effectively discriminates neutrons and gamma rays by examining the frequency-domain features of the photomultiplier tube anode signal. This approach is insensitive to noise but is inevitably affected by the baseline drift, similar to other pulse shape discrimination methods. The baseline drift effect is attributed to the factors such as power line fluctuation, dark current, noise disturbances, hum, and pulse tail in front-end electronics. This effect needs to be elucidated and quantified before the baseline shift can be estimated and removed from the captured signal. Therefore, the effect of baseline shift on the discrimination performance of neutrons and gamma rays with organic scintillation detectors using FGA is investigated in this paper. The relationship between the baseline shift and discrimination parameters of FGA is derived and verified by an experimental system consisting of an americium-beryllium source, a BC501A liquid scintillator detector, and a 5 GSPS 8-bit oscilloscope. Both theoretical and experimental results show that the estimation of the baseline shift is necessary, and the removal of baseline drift from the pulse shapes can improve the discrimination performance of FGA.

Guofu Liu; Xiaoliang Luo; Jun Yang; Cunbao Lin; Qingqing Hu; Jinxian Peng

2013-05-08T23:59:59.000Z

380

Non-thermal X-ray and Gamma-ray Emission from the Colliding Wind Binary WR140  

E-Print Network (OSTI)

WR140 is the archetype long-period colliding wind binary (CWB) system, and is well known for dramatic variations in its synchrotron emission during its 7.9-yr, highly eccentric orbit. This emission is thought to arise from relativistic electrons accelerated at the global shocks bounding the wind-collision region (WCR). The presence of non-thermal electrons and ions should also give rise to X-ray and gamma-ray emission from several separate mechanisms, including inverse-Compton cooling, relativistic bremsstrahlung, and pion decay. We describe new calculations of this emission and make some preliminary predictions for the new generation of gamma-ray observatories. We determine that WR140 will likely require several Megaseconds of observation before detection with INTEGRAL, but should be a reasonably strong source for GLAST.

J. M. Pittard; S. M. Dougherty

2005-09-30T23:59:59.000Z

Note: This page contains sample records for the topic "gamma-ray logging systems" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


381

Response of a LaBr3(Ce) Detector to 2-11 MeV Gamma Rays  

DOE Green Energy (OSTI)

The development of lanthanum halide scintillation detectors has great potential application in field-portable prompt-gamma neutron activation analysis systems. Because the low-energy response of these detectors has already been well-characterized [1[-[2], we have measured their response to higher energy gamma rays in the region between 2 and 11 MeV. We have measured the response of a 2-inch (5.08 cm) by 2-inch long LaBr3(Ce) detector to high energy gamma rays produced by neutron interactions on chlorine, hydrogen, iron, nitrogen, phosphorous, and sulfur. The response of the LaBr3(Ce) detector is compared to that of HPGe and NaI(Tl) detectors.

Not Available

2006-10-01T23:59:59.000Z

382

Design and imaging performance of achromatic diffractive/refractive X-ray and Gamma-ray Fresnel lenses  

E-Print Network (OSTI)

Achromatic combinations of a diffractive Phase Fresnel Lens and a refractive correcting element have been proposed for X-ray and gamma-ray astronomy and for microlithography, but considerations of absorption often dictate that the refractive component be given a stepped profile, resulting in a double Fresnel lens. The imaging performance of corrected Fresnel lenses, with and without `stepping' is investigated and the trade-off between resolution and useful bandwidth in different circumstances is discussed. Provided the focal ratio is large, correction lenses made of low atomic number materials can be used with X-rays in the range approximately 10--100 keV without stepping. The use of stepping extends the possibility of correction to higher aperture systems, to energies as low as a few kilo electron volts and to gamma-rays of $\\sim$ mega electron volt energy.

Gerald K. Skinner

2004-07-21T23:59:59.000Z

383

Fermi LAT Observation of Diffuse Gamma-Rays Produced through Interactions Between Local Interstellar Matter and High Energy Cosmic Rays  

DOE Green Energy (OSTI)

Observations by the Large Area Telescope (LAT) on the Fermi mission of diffuse {gamma}-rays in a mid-latitude region in the third quadrant (Galactic longitude l from 200{sup o} to 260{sup o} and latitude |b| from 22{sup o} to 60{sup o}) are reported. The region contains no known large molecular cloud and most of the atomic hydrogen is within 1 kpc of the solar system. The contributions of {gamma}-ray point sources and inverse Compton scattering are estimated and subtracted. The residual {gamma}-ray intensity exhibits a linear correlation with the atomic gas column density in energy from 100 MeV to 10 GeV. The measured integrated {gamma}-ray emissivity is (1.63 {+-} 0.05) x 10{sup -26} photons s{sup -1}sr{sup -1} H-atom{sup -1} and (0.66 {+-} 0.02) x 10{sup -26} photons s{sup -1}sr{sup -1} H-atom{sup -1} above 100 MeV and above 300 MeV, respectively, with an additional systematic error of {approx}10%. The differential emissivity from 100 MeV to 10 GeV agrees with calculations based on cosmic ray spectra consistent with those directly measured, at the 10% level. The results obtained indicate that cosmic ray nuclei spectra within 1 kpc from the solar system in regions studied are close to the local interstellar spectra inferred from direct measurements at the Earth within {approx}10%.

Abdo, A.A.; /Naval Research Lab, Wash., D.C. /Federal City Coll.; Ackermann, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Ajello, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Atwood, W.B.; /UC, Santa Cruz; Axelsson, M.; /Stockholm U. /Stockholm U., OKC; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Barbiellini, G.; /INFN, Trieste /Trieste U.; Bastieri, D.; /INFN, Padua /Padua U.; Baughman, B.M.; /Ohio State U.; Bechtol, K.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bellazzini, R.; /INFN, Pisa; Berenji, B.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bloom, E.D.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bonamente, E.; /INFN, Perugia /Perugia U.; Borgland, A.W.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bregeon, J.; /INFN, Pisa; Brez, A.; /INFN, Pisa; Brigida, M.; /Bari U. /INFN, Bari; Bruel, P.; /Ecole Polytechnique; Burnett, T.H.; /Washington U., Seattle /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /IASF, Milan /Milan Polytechnic /Royal Inst. Tech., Stockholm /Stockholm U., OKC /DAPNIA, Saclay /INFN, Perugia /Perugia U. /NASA, Goddard /Naval Research Lab, Wash., D.C. /George Mason U. /NASA, Goddard /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Montpellier U. /Stockholm U. /Stockholm U., OKC /Royal Inst. Tech., Stockholm /ASDC, Frascati /Naval Research Lab, Wash., D.C. /INFN, Trieste /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /CENBG, Gradignan /CENBG, Gradignan /Montpellier U. /Bari U. /INFN, Bari /Ecole Polytechnique /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /INFN, Trieste /Hiroshima U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Bari U. /INFN, Bari /INFN, Bari; /more authors..

2012-03-30T23:59:59.000Z

384

Microsoft Word - scr-log  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

Control Log Page : Log Date: System Name: Approval Status SCR Reqmnt Date Submitted Priority (E,U,R) * Change Approved Change Not Approved Hold (Future...

385

Andromeda: A mission to determine the gamma-ray burst distance scale F.A. Harrison, W.R. Cook, T.A. Prince, S.M. Schindler  

E-Print Network (OSTI)

V emission from the galactic plane, and a search for transient emission above 100 GeV from gamma ray bursts- clei (AGN), supernova remnants and gamma-ray bursts (GRB). Gamma rays are also produced when high data will yield im- proved results. #12;3 5. Gamma-Ray Burst Search Sensitivity TeV gamma rays

Prince, Thomas A.

386

SCINTILLATION DETECTOR COOLING SYSTEM  

SciTech Connect

A well logging apparatus for irradiating earth formations with neutrons and recording the gamma rays emitted therefrom is designed which hss a scintillation decay time of less than 3 x 10/sup -8/ sec and hence may be used with more intense neutron sources. The scintillation crystal is an unactivated NaI crystal maintained at liquid N/sub 2/ temperature. The apparatus with the cooling system is described in detail. (D.L.C.)

George, W.D.; Jones, S.B.; Yule, H.P.

1962-08-14T23:59:59.000Z

387

Gamma Ray Burst Section of the White Paper on the Status and Future of Ground-based TeV Gamma-ray Astronomy  

E-Print Network (OSTI)

This is a report on the findings of the gamma ray burst working group for the white paper on the status and future of TeV gamma-ray astronomy. The white paper is an APS commissioned document, and the overall version has also been released and can be found on astro-ph. This detailed section of the white paper discusses the status of past and current attempts to observe gamma ray bursts at GeV-TeV energies. We concentrate on the potential of future ground-based gamma-ray experiments to observe the highest energy emission ever recorded for GRBs, particularly for those that are nearby and have high Lorentz factors in the GRB jet. It is clear that major advances are possible and that the detection of very high energy emission would have strong implications for GRB models, as well as cosmic ray origin.

A. D. Falcone; D. A. Williams; M. G. Baring; R. Blandford; J. Buckley; V. Connaughton; P. Coppi; C. Dermer; B. Dingus; C. Fryer; N. Gehrels; J. Granot; D. Horan; J. I. Katz; K. Kuehn; P. Meszaros; J. Norris; P. Saz Parkinson; A. Pe'er; E. Ramirez-Ruiz; S. Razzaque; X. Y. Wang; B. Zhang

2008-10-02T23:59:59.000Z

388

Gamma Ray Burst Section of the White Paper on the Status and Future of Ground-based TeV Gamma-ray Astronomy  

E-Print Network (OSTI)

This is a report on the findings of the gamma ray burst working group for the white paper on the status and future of TeV gamma-ray astronomy. The white paper is an APS commissioned document, and the overall version has also been released and can be found on astro-ph. This detailed section of the white paper discusses the status of past and current attempts to observe gamma ray bursts at GeV-TeV energies. We concentrate on the potential of future ground-based gamma-ray experiments to observe the highest energy emission ever recorded for GRBs, particularly for those that are nearby and have high Lorentz factors in the GRB jet. It is clear that major advances are possible and that the detection of very high energy emission would have strong implications for GRB models, as well as cosmic ray origin.

Falcone, A D; Baring, M G; Blandford, R; Buckley, J; Connaughton, V; Coppi, P; Dermer, C; Dingus, B; Fryer, C; Gehrels, N; Granot, J; Horan, D; Katz, J I; Kühn, K; Mészáros, P; Norris, J; Parkinson, P Saz; Peér, A; Ramirez-Ruiz, E; Razzaque, S; Wang, X Y; Zhang, B

2008-01-01T23:59:59.000Z

389

Gamma-Ray Bursts - a Primer For Relativists  

E-Print Network (OSTI)

Gamma-Ray Bursts (GRBs) - short bursts of 100-1MeV photons arriving from random directions in the sky are probably the most relativistic objects discovered so far. Still, somehow they did not attract the attention of the relativistic community. In this short review I discuss briefly GRB observations and show that they lead us to the fireball model - GRBs involve macroscopic relativistic motion with Lorentz factors of a few hundred or more. I show that GRB sources involve, most likely, new born black holes, and their progenitors are Supernovae or neutron star mergers. I show that both GRB progenitors and the process of GRB itself produce gravitational radiation and I consider the possibility of detecting this emission. Finally I show that GRBs could serve as cosmological indicators that could teach us about the high redshift ($z \\approx 5-15$) dark ages of the universe.

Tsvi Piran

2002-05-12T23:59:59.000Z

390

Quantifying the Luminosity Evolution in Gamma-ray Bursts  

E-Print Network (OSTI)

We estimate the luminosity evolution and formation rate for over 900 GRBs by using redshift and luminosity data calculated by Band, Norris, $&$ Bonnell (2004) via the lag-luminosity correlation. By applying maximum likelihood techniques, we are able to infer the true distribution of the parent GRB population's luminosity function and density distributions in a way that accounts for detector selection effects. We find that after accounting for data truncation, there still exists a significant correlation between the average luminosity and redshift, indicating that distant GRBs are on average more luminous than nearby counterparts. This is consistent with previous studies showing strong source evolution and also recent observations of under luminous nearby GRBs. We find no evidence for beaming angle evolution in the current sample of GRBs with known redshift, suggesting that this increase in luminosity can not be due to an evolution of the collimation of gamma-ray emission. The resulting luminosity function...

Kocevski, D; Kocevski, Daniel; Liang, Edison

2006-01-01T23:59:59.000Z

391

Fermi-LAT and the Gamma-Ray Line Search  

E-Print Network (OSTI)

A distinct signature for dark matter in the form of weakly interacting massive particles (WIMPs) would be the detection of a monochromatic spectral line in the gamma-ray sky. The Fermi-LAT collaboration has searched for such a line in the energy range from 5 to 300 GeV in five sky regions around the Galactic centre. No globally significant line is detected, and 95% CL upper limits on monochromatic-line strengths are presented. The smallest search region reveals a line-like structure at 133 GeV with a local significance of 2.9 sigma after 4.4 years of data, which translates to less than 1 sigma global significance from a trial factor of around 200.

Gustafsson, Michael

2013-01-01T23:59:59.000Z

392

Finding (Or Not) New Gamma-Ray Pulsars with GLAST  

SciTech Connect

Young energetic pulsars will likely be the largest class of Galactic sources observed by GLAST, with many hundreds detected. Many will be unknown as radio pulsars, making pulsation detection dependent on radio and/or x-ray observations or on blind periodicity searches of the gamma-rays. Estimates for the number of pulsars GLAST will detect in blind searches have ranged from tens to many hundreds. I argue that the number will be near the low end of this range, partly due to observations being made in a scanning as opposed to a pointing mode. This paper briefly reviews how blind pulsar searches will be conducted using GLAST, what limits these searches, and how the computations and statistics scale with various parameters.

Ransom, Scott M.; /NRAO, Charlottesville

2011-11-29T23:59:59.000Z

393

Polarized Gravitational Waves from Gamma-Ray Bursts  

E-Print Network (OSTI)

Significant gravitational wave emission is expected from gamma-ray bursts arising from compact stellar mergers, and possibly also from bursts associated with fast-rotating massive stellar core collapses. These models have in common a high angular rotation rate, and observations provide evidence for jet collimation of the photon emission, with properties depending on the polar angle, which may also be of relevance for X-ray flashes. Here we consider the gravitational wave emission and its polarization as a function of angle which is expected from such sources. We discuss possible correlations between the burst photon luminosity, or the delay between gravitational wave bursts and X-ray flashes, and the polarization degree of the gravitational waves.

Shiho Kobayashi; Peter Meszaros

2002-12-25T23:59:59.000Z

394

Cosmic Gamma-Ray Bursts The Remaining Mysteries  

E-Print Network (OSTI)

To anyone who has read a scientific journal or even a newspaper in the last six months, it might appear that cosmic gamma-ray bursts hold no more mysteries: they are cosmological, and possibly the most powerful explosions in the Universe. In fact, however, bursts remain mysterious in many ways. There is no general agreement upon the nature of the event which releases the initial energy. One burst at least appears to strain the energy budget of the merging neutron star model. There is evidence that another recent event may have come from a nearby supernova. Finally, while the number count statistics clearly show a strong deviation from the -3/2 power law expected for a Euclidean, homogeneous distribution, the distributions of some classes of bursts appear to follow a -3/2 power law rather closely. The recent data on bursts is reviewed, some of the mysteries discussed, and future experiments are outlined.

Hurley, K

1998-01-01T23:59:59.000Z

395

Testing Mass Varying Neutrino With Short Gamma Ray Burst  

E-Print Network (OSTI)

In this paper we study the possibility of probing for the absolute neutrino mass and its variation with short Gamma Ray Burst (GRB). We have calculated the flight time difference between a massive neutrino and a photon in two different approaches to mass varying neutrinos. Firstly we parametrize the neutrino mass as a function of redshift in a model independent way, then we consider two specific models where the neutrino mass varies during the evolution of the Quintessence fields. Our calculations show in general the value of the time delay is changed substantially relative to a constant neutrino mass. Furthermore our numerical results show that the flight time delay in these models is expected to be larger than the duration time of the short GRB, which opens a possibility of testing the scenario of mass varying neutrino with the short GRB.

Hong Li; Zigao Dai; Xinmin Zhang

2004-11-17T23:59:59.000Z

396

Gravitational Wave Memory of Gamma-Ray Burst Jets  

E-Print Network (OSTI)

Gamma-Ray Bursts (GRBs) are now considered as relativistic jets. We analyze the gravitational waves from the acceleration stage of the GRB jets. We show that (i) the point mass approximation is not appropriate if the opening half-angle of the jet is larger than the inverse of the Lorentz factor of the jet, (ii) the gravitational waveform has many step function like jumps, and (iii) the practical DECIGO and BBO may detect such an event if the GRBs occur in Local group of galaxy. We found that the light curve of GRBs and the gravitational waveform are anti-correlated so that the detection of the gravitational wave is indispensable to determine the structure of GRB jets.

Norichika Sago; Kunihito Ioka; Takashi Nakamura; Ryo Yamazaki

2004-05-13T23:59:59.000Z

397

Study of Lorentz violation in INTEGRAL Gamma-Ray Bursts  

E-Print Network (OSTI)

We search for possible time lags caused by quantum gravitational (QG) effects using gamma-ray bursts (GRBs) detected by INTEGRAL. The advantage of this satellite is that we have at our disposal the energy and arrival time of every detected single photon, which enhances the precision of the time resolution. We present a new method for seeking time lags in unbinned data using a maximum likelihood method and support our conclusions with Monte Carlo simulations. The analysis of the data yields a mass scale well below the Planck mass whose value may however increase if better statistics of GRBs were available. Furthermore, we disagree with previous studies in which a non-monotonic function of the redshift was used to perform a linear fit.

Raphael Lamon; Nicolas Produit; Frank Steiner

2007-06-27T23:59:59.000Z

398

General Relativistic Binary Merger Simulations and Short Gamma Ray Bursts  

E-Print Network (OSTI)

The recent localization of some short-hard gamma ray bursts (GRBs) in galaxies with low star formation rates has lent support to the suggestion that these events result from compact object binary mergers. We discuss how new simulations in general relativity are helping to identify the central engine of short-hard GRBs. Motivated by our latest relativistic black hole-neutron star merger calculations, we discuss a scenario in which these events may trigger short-hard GRBs, and compare this model to competing relativistic models involving binary neutron star mergers and the delayed collapse of hypermassive neutron stars. Distinguishing features of these models may help guide future GRB and gravitational wave observations to identify the nature of the sources.

Joshua A. Faber; Thomas W. Baumgarte; Stuart L. Shapiro; Keisuke Taniguchi

2006-03-10T23:59:59.000Z

399

The Status and future of ground-based TeV gamma-ray astronomy. A White Paper prepared for the Division of Astrophysics of the American Physical Society  

E-Print Network (OSTI)

In recent years, ground-based TeV gamma-ray observatories have made spectacular discoveries including imaging spectroscopy observations of galactic sources of different classes, and the discovery of rapid gamma-ray flares from radio galaxies and active galactic nuclei containing supermassive black holes. These discoveries, and the fact that gamma-ray astronomy has the potential to map the radiation from dark matter annihilation in our Galaxy and in extragalactic systems, have attracted the attention of the wider scientific community. The Division of Astrophysics of the American Physical Society requested the preparation of a white paper on the status and future of ground-based gamma-ray astronomy to define the science goals of a future observatory, to determine the performance specifications, to identify the areas of necessary technology development, and to lay out a clear path for proceeding beyond the near term. The white paper was written with broad community input, including discussions on several dedicat...

Buckley, J; Dingus, B; Falcone, A; Kaaret, Philip; Krawzcynski, H; Pohl, M; Vasilev, V; Williams, D A

2008-01-01T23:59:59.000Z

400

Study of galactic gamma ray sources with Milagro Jordan A. Goodman for the Milagro Collaboration  

E-Print Network (OSTI)

Study of galactic gamma ray sources with Milagro Jordan A. Goodman for the Milagro Collaboration. This factor of ~2 increase in sensitivity (as shown in figure 1) has dramatically changed our view of the high-energy Galactic gamma-ray emission at TeV energies, including the detection of the Cygnus Region at high

California at Santa Cruz, University of

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401

Title of dissertation: A SEARCH FOR BURSTS OF VERY HIGH ENERGY GAMMA RAYS  

E-Print Network (OSTI)

ABSTRACT Title of dissertation: A SEARCH FOR BURSTS OF VERY HIGH ENERGY GAMMA RAYS WITH MILAGRO Vlasios Vasileiou, Doctor of Philosophy, 2008 Dissertation directed by: Professor Jordan A. Goodman by cosmic gamma rays of energies E 100 GeV . The effective area of Milagro peaks at energies E 10 Te

California at Santa Cruz, University of

402

Fermi Large Area Telescope Measurements of the Diffuse Gamma-Ray Emission at Intermediate Galactic Latitudes  

SciTech Connect

The diffuse galactic {gamma}-ray emission is produced by cosmic rays (CRs) interacting with the interstellar gas and radiation field. Measurements by the Energetic Gamma-Ray Experiment Telescope (EGRET) instrument on the Compton Gamma-Ray Observatory indicated excess {gamma}-ray emission {ge}1 GeV relative to diffuse galactic {gamma}-ray emission models consistent with directly measured CR spectra (the so-called 'EGRET GeV excess'). The Large Area Telescope (LAT) instrument on the Fermi Gamma-Ray Space Telescope has measured the diffuse {gamma}-ray emission with improved sensitivity and resolution compared to EGRET. We report on LAT measurements for energies 100 MeV to 10 GeV and galactic latitudes 10{sup o} {le} |b| {le} 20{sup o}. The LAT spectrum for this region of the sky is well reproduced by a diffuse galactic {gamma}-ray emission model that is consistent with local CR spectra and inconsistent with the EGRET GeV excess.

Abdo, A.A.; /Naval Research Lab, Wash., D.C.; Ackermann, M.; Ajello, M.; /SLAC; Anderson, B.; Atwood, W.B.; /UC, Santa Cruz; Axelsson, M.; /Stockholm U. /Stockholm U., OKC; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Barbiellini, G.; /INFN, Trieste /Trieste U.; Bastieri, D.; /INFN, Padua /Padua U.; Baughman, B.M.; /Taiwan, Natl. Taiwan U. /Ohio State U.; Bechtol, K.; /SLAC; Bellazzini, R.; /INFN, Pisa; Berenji, B.; Blandford, R.D.; Bloom, E.D.; /SLAC; Bonamente, E.; /INFN, Perugia /Perugia U.; Borgland, A.W.; /SLAC; Bregeon, J.; Brez, A.; /INFN, Pisa; Brigida, M.; /Bari U. /INFN, Bari /Ecole Polytechnique /Washington U., Seattle /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /IASF, Milan /DAPNIA, Saclay /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Naval Research Lab, Wash., D.C. /George Mason U. /NASA, Goddard /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Montpellier U. /Stockholm U. /Stockholm U., OKC /Royal Inst. Tech., Stockholm /Padua U. /Naval Research Lab, Wash., D.C. /Udine U. /INFN, Trieste /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /INFN, Pisa /UC, Santa Cruz /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /CENBG, Gradignan /CENBG, Gradignan /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Montpellier U. /Bari U. /INFN, Bari /Ecole Polytechnique /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Udine U. /INFN, Trieste /Hiroshima U. /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Bari U. /INFN, Bari /INFN, Pisa /INFN, Bari /NASA, Goddard /Maryland U.; /more authors..

2012-04-11T23:59:59.000Z

403

Very High Energy Observations of Satellite?Detected Gamma?Ray Bursts  

Science Conference Proceedings (OSTI)

Recent results from the Fermi Gamma?ray Space Telescope indicate that gamma?ray bursts (GRBs) are capable of producing photons with energies up to ?90 GeV in the rest frame of the burst. The Fermi?LAT may not be sensitive to the highest energy photons associated with GRBs and ground?based

Taylor Aune; The Milagro Collaboration; The VERITAS collaboration

2011-01-01T23:59:59.000Z

404

Swift Pointing and Gravitational-Wave Bursts from Gamma-Ray Burst Events  

E-Print Network (OSTI)

The currently accepted model for gamma-ray burst phenomena involves the violent formation of a rapidly rotating solar-mass black hole. Gravitational waves should be associated with the black-hole formation, and their detection would permit this model to be tested. Even upper limits on the gravitational-wave strength associated with gamma-ray bursts could constrain the gamma-ray burst model. This requires joint observations of gamma-ray burst events with gravitational and gamma-ray detectors. Here we examine how the quality of an upper limit on the gravitational-wave strength associated with gamma-ray bursts depends on the relative orientation of the gamma-ray-burst and gravitational-wave detectors, and apply our results to the particular case of the Swift Burst-Alert Telescope (BAT) and the LIGO gravitational-wave detectors. A result of this investigation is a science-based ``figure of merit'' that can be used, together with other mission constraints, to optimize the pointing of the Swift telescope for the detection of gravitational waves associated with gamma-ray bursts.

Lee Samuel Finn; Badri Krishnan; Patrick J. Sutton

2003-04-23T23:59:59.000Z

405

HETE, the High Energy Transient Explorer : unlocking the mysteries of gamma ray bursts  

E-Print Network (OSTI)

The High Energy Transient Explorer (HETE), was built primarily at MIT and launched in October 2000 with the goal of studying Gamma Ray Bursts (GRBs) at X-ray and gamma-ray energies. A suite of instruments aboard HETE provide ...

Monnelly, Glen Pickslay, 1973-

2002-01-01T23:59:59.000Z

406

Search for GeV Emission from Gamma-Ray Bursts Using Milagro Scaler Data  

E-Print Network (OSTI)

Prompt and Delayed High­Energy Emission from Cosmological Gamma­Ray Bursts Markus B¨ottcher a, Washington, DC 20375­5352 Abstract In the cosmological blast­wave model for gamma ray bursts (GRBs), high if they are indeed associated with star­forming regions. 3 Comparison with Gamma Rays from Hadronic Processes

California at Santa Cruz, University of

407

Neutrinos from gamma-ray bursts as a tool to explore quantum-gravity-induced  

E-Print Network (OSTI)

LETTERS Neutrinos from gamma-ray bursts as a tool to explore quantum-gravity-induced Lorentz energy scale. According to existing models, gamma-ray bursts (GRBs) are accompanied by very high from the same direction as a GRB, months after the burst, would be statistically significant and imply

Loss, Daniel

408

Short gamma-ray bursts from binary neutron star mergers in globular clusters  

E-Print Network (OSTI)

ARTICLES Short gamma-ray bursts from binary neutron star mergers in globular clusters JONATHAN@cfa.harvard.edu Published online: 29 January 2006; doi:10.1038/nphys214 Observations by the Swift gamma-ray-burst (GRB, the so-called `long' GRBs (>2-200 s) were located by coded aperture imaging of their hard X-ray emission

Loss, Daniel

409

Gamma-ray energies for calibration of Ge(Li) spectrometers  

SciTech Connect

Gamma-ray energies are compared for bent-crystal measurements, Ge(Li) measurements, and other measurements. 150 gamma-ray energies below 3450 keV from 35 isotopes are being calibrated for calibration of Ge(Li) spectrometers. (WHK)

Helmer, R.G.; Greenwood, R.C.; Gehrke, R.J.

1975-01-01T23:59:59.000Z

410

Direction-Sensitive Hand-Held Gamma-Ray Spectrometer  

SciTech Connect

A novel, light-weight, hand-held gamma-ray detector with directional sensitivity is being designed. The detector uses a set of multiple rings around two cylindrical surfaces, which provides precise location of two interaction points on two concentric cylindrical planes, wherefrom the source location can be traced back by back projection and/or Compton imaging technique. The detectors are 2.0 × 2.0 mm europium-doped strontium iodide (SrI2:Eu2+) crystals, whose light output has been measured to exceed 120,000 photons/MeV, making it one of the brightest scintillators in existence. The crystal’s energy resolution, less than 3% at 662 keV, is also excellent, and the response is highly linear over a wide range of gamma-ray energies. The emission of SrI2:Eu2+ is well matched to both photo-multiplier tubes and blue-enhanced silicon photodiodes. The solid-state photomultipliers used in this design (each 2.0 × 2.0 mm) are arrays of active pixel sensors (avalanche photodiodes driven beyond their breakdown voltage in reverse bias); each pixel acts as a binary photon detector, and their summed output is an analog representation of the total photon energy, while the individual pixel accurately defines the point of interaction. A simple back-projection algorithm involving cone-surface mapping is being modeled. The back projection for an event cone is a conical surface defining the possible location of the source. The cone axis is the straight line passing through the first and second interaction points.

Mukhopadhyay, S.

2012-10-04T23:59:59.000Z

411

Propagation of Neutrinos through Magnetized Gamma-Ray Burst Fireball  

E-Print Network (OSTI)

The neutrino self-energy is calculated in a weakly magnetized plasma consists of electrons, protons, neutrons and their anti-particles and using this we have calculated the neutrino effective potential up to order $M^{-4}_W$. In the absence of magnetic field it reduces to the known result. We have also calculated explicitly the effective potentials for different backgrounds which may be helpful in different environments. By considering the mixing of three active neutrinos in the medium with the magnetic field we have derived the survival and conversion probabilities of neutrinos from one flavor to another and also the resonance condition is derived. As an application of the above, we considered the dense and relativistic plasma of the Gamma-Ray Bursts fireball through which neutrinos of 5-30 MeV can propagate and depending on the fireball parameters they may oscillate resonantly or non-resonantly from one flavor to another. These MeV neutrinos are produced due to stellar collapse or merger events which trigger the Gamma-Ray Burst. The fireball itself also produces MeV neutrinos due to electron positron annihilation, inverse beta decay and nucleonic bremsstrahlung. Using the three neutrino mixing and considering the best fit values of the neutrino parameters, we found that electron neutrinos are hard to oscillate to another flavors. On the other hand, the muon neutrinos and the tau neutrinos oscillate with equal probability to one another, which depends on the neutrino energy, temperature and size of the fireball. Comparison of oscillation probabilities with and without magnetic field shows that, they depend on the neutrino energy and also on the size of the fireball. By using the resonance condition, we have also estimated the resonance length of the propagating neutrinos as well as the baryon content of the fireball.

Sarira Sahu; Nissim Fraija; Yong-Yeon Keum

2009-09-16T23:59:59.000Z

412

GLAST Observatory Renamed for Fermi, Reveals Entire Gamma-Ray Sky |  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

GLAST Observatory Renamed for Fermi, Reveals Entire Gamma-Ray Sky GLAST Observatory Renamed for Fermi, Reveals Entire Gamma-Ray Sky GLAST Observatory Renamed for Fermi, Reveals Entire Gamma-Ray Sky August 26, 2008 - 3:20pm Addthis WASHINGTON, D.C. - The U.S. Department of Energy (DOE) and NASA announced today that the Gamma-Ray Large Area Space Telescope (GLAST) has revealed its first all-sky map in gamma rays. The onboard Large Area Telescope's (LAT) all-sky image-which shows the glowing gas of the Milky Way, blinking pulsars and a flaring galaxy billions of light-years away-was created using only 95 hours of "first light" observations, compared with past missions which took years to produce a similar image. Scientists expect the telescope will discover many new pulsars in our own galaxy, reveal powerful

413

Using gamma-ray emission to measure areal density of ICF capsules  

SciTech Connect

Fusion neutrons streaming from a burning ICF capsule generate gamma rays via nuclear inelastic scattering in the ablator of the capsule. The intensity of gamma-ray emission is proportional to the product of the ablator areal density ('{rho}R') and the yield of fusion neutrons, so by detecting the gamma rays we can infer the ablator areal density, provided we also have a measurement of the capsule's total neutron yield. In plastic-shell capsules, for example, {sup 12}C nuclei emit gamma rays at 4.44 MeV after excitation by 14.1-MeV neutrons from D+T fusion. These gamma rays can be measured by the Gamma Reaction History (GRH) experiment being built at the National Ignition Facility (NIF). A linear error analysis indicates the chief sources of uncertainty in inferred areal density.

Hoffman, Nelson M [Los Alamos National Laboratory; Wilson, Douglas C [Los Alamos National Laboratory; Hermann, Hans W [Los Alamos National Laboratory; Young, Carlton S [Los Alamos National Laboratory

2010-01-01T23:59:59.000Z

414

Precision linac and laser technologies for nuclear photonics gamma-ray sources  

SciTech Connect

Tunable, high precision gamma-ray sources are under development to enable nuclear photonics, an emerging field of research. This paper focuses on the technological and theoretical challenges related to precision Compton scattering gamma-ray sources. In this scheme, incident laser photons are scattered and Doppler upshifted by a high brightness electron beam to generate tunable and highly collimated gamma-ray pulses. The electron and laser beam parameters can be optimized to achieve the spectral brightness and narrow bandwidth required by nuclear photonics applications. A description of the design of the next generation precision gamma-ray source currently under construction at Lawrence Livermore National Laboratory is presented, along with the underlying motivations. Within this context, high-gradient X-band technology, used in conjunction with fiber-based photocathode drive laser and diode pumped solid-state interaction laser technologies, will be shown to offer optimal performance for high gamma-ray spectral flux, narrow bandwidth applications.

Albert, F.; Hartemann, F. V.; Anderson, S. G.; Cross, R. R.; Gibson, D. J.; Hall, J.; Marsh, R. A.; Messerly, M.; Wu, S. S.; Siders, C. W.; Barty, C. P. J. [Lawrence Livermore National Laboratory, NIF and Photon Science, 7000 East Avenue, Livermore, California 94550 (United States)

2012-05-15T23:59:59.000Z

415

Logging-while-coring method and apparatus  

DOE Patents (OSTI)

A method and apparatus for downhole coring while receiving logging-while-drilling tool data. The apparatus includes core collar and a retrievable core barrel. The retrievable core barrel receives core from a borehole which is sent to the surface for analysis via wireline and latching tool The core collar includes logging-while-drilling tools for the simultaneous measurement of formation properties during the core excavation process. Examples of logging-while-drilling tools include nuclear sensors, resistivity sensors, gamma ray sensors, and bit resistivity sensors. The disclosed method allows for precise core-log depth calibration and core orientation within a single borehole, and without at pipe trip, providing both time saving and unique scientific advantages.

Goldberg, David S. (New York, NY); Myers, Gregory J. (Cornwall, NY)

2007-11-13T23:59:59.000Z

416

Results of 1999 Spectral Gamma-Ray and Neutron Moisture Monitoring of Boreholes at Specific Retention Facilities in the 200 East Area, Hanford Site  

SciTech Connect

Twenty-eight wells and boreholes in the 200 East Are% Hanford Site, Washington were monitored in 1999. The monitored facilities were past-practice liquid waste disposal facilities and consisted of six cribs and nineteen ''specific retention'' cribs and trenches. Monitoring consisted of spectral gamma-ray and neutron moisture logging. All data are included in Appendix B. The isotopes {sup 137}Cs, {sup 60}Co, {sup 235}U, {sup 238}U, and {sup 154}Eu were identified on spectral gamma logs from boreholes monitoring the PUREX specific retention facilities; the isotopes {sup 137}Cs, {sup 60}Co, {sup 125}Sb, and {sup 154}Eu were identified on the logs from boreholes at the BC Controlled Area cribs and trenches; and {sup 137}Cs, {sup 60}Co, and {sup 125}Sb were, identified on the logs from boreholes at the BX specific retention trenches. Three boreholes in the BC Controlled Area and one at the BX trenches had previous spectral gamma logs available for comparison with 1999 logs. Two of those logs showed that changes in the subsurface distribution of {sup 137}CS and/or {sup 60}Co had occurred since 1992. Although the changes are not great, they do point to continued movement of contaminants in the vadose zone. The logs obtained in 1999 create a larger baseline for comparison with future logs. Numerous historical gross gamma logs exist from most of the boreholes logged. Qualitative comparison of those logs with the 1999 logs show many substantial changes, most of which reflect the decay of deeper short-lived isotopes, such as {sup 106}Ru and {sup 125}Sb, and the much slower decay of shallower and longer-lived isotopes such as {sup 137}Cs. The radionuclides {sup 137}Cs and {sup 60}Co have moved in two boreholes since 1992. Given the amount of movement and the half-lives of the isotopes, it is expected that they will decay to insignificant amounts before reaching groundwater. However, gamma ray logging cannot detect many of the contaminants of interest such as {sup 99}Tc, NO{sub 3}, or {sup 129}I, all of which can be highly mobile in the vadose zone and, for the radionuclides, have long half-lives.

DG Horton; RR Randall

2000-01-18T23:59:59.000Z

417

A Search for Muon Neutrinos from Gamma-Ray Bursts wih the IceCube 22-String Detector.  

E-Print Network (OSTI)

??Two searches are conducted for muon neutrinos from Gamma-Ray Bursts (GRBs) using the IceCube detector. Gamma-Ray Bursts are brief and transient emissions of keV/MeV radiation… (more)

Roth, A Philip

2009-01-01T23:59:59.000Z

418

H.E.S.S. upper limit on the very high energy gamma-ray emission from the globular cluster 47 Tucanae  

E-Print Network (OSTI)

Observations of the globular cluster 47 Tucanae (NGC 104), which contains at least 23 millisecond pulsars, were performed with the H.E.S.S. telescope system. The observations lead to an upper limit of F(E>800 GeV) conversion efficiency of spin-down power to gamma-ray photons or to relativistic leptons.

Aharonian, F

2009-01-01T23:59:59.000Z

419

Thermoluminescence dosimetry of gamma rays from the atomic bomb at Hiroshima using the predose technique  

Science Conference Proceedings (OSTI)

Thermoluminescence dosimetry measurements of gamma rays produced by the atomic bomb in Hiroshima were made by the predose technique using eight ceramic samples collected from five buildings located at distances between 1271 and 2051 m from the hypocenter. The results of our measurements are compared to both the newer dose estimates (Dosimetry System 1986) and older dose estimates (Tentative 1965 Doses) for survivors of the Hiroshima atomic bomb. In comparison with the older estimates, our results are larger by a factor of 2.3 at 1271 m and 3.9 at 2051 m. Our results and the newer estimates for Hiroshima differ by a factor of only 1.14 +/- 0.16 on the average.

Nagatomo, T.; Ichikawa, Y.; Ishii, H.; Hoshi, M.

1988-02-01T23:59:59.000Z

420

The Performance of the Gamma-Ray Energy Tracking In-Beam Nuclear Array GRETINA  

SciTech Connect

The Gamma-Ray Energy Tracking In-beam Nuclear Array (GRETINA) is a new generation high-resolution -ray spectrometer consisting of electrically segmented high-purity germanium crystals. GRETINA is capable of reconstructing the energy and position of each -ray interaction point inside the crystal with high resolution. This enables -ray energy tracking which in turn provides an array with large photopeak efficiency, high resolution and good peak-to-total ratio. GRETINA is used for nuclear structure studies with demanding -ray detection requirements and it is suitable for experiments with radioactive-ion beams with high recoil velocities. The GRETINA array has a 1 solid angle coverage and constitutes the first stage towards the full 4 array GRETA. We present in this paper the main parts and the performance of the GRETINA system.

Paschalis, S. [Lawrence Berkeley National Laboratory (LBNL); Lee, I. Y. [Lawrence Berkeley National Laboratory (LBNL); Macchiavelli, A. O. [Lawrence Berkeley National Laboratory (LBNL); Campbell, C. M. [Lawrence Berkeley National Laboratory, The Scripps Research Institite and The Skaggs Institute; Cromaz, M. [Lawrence Berkeley National Laboratory (LBNL); Gros, S. [Lawrence Berkeley National Laboratory (LBNL); Pavin, J. [Lawrence Berkeley National Laboratory (LBNL); Qian, J. [Lawrence Berkeley National Laboratory (LBNL); Clark, R. M. [Lawrence Berkeley National Laboratory (LBNL); Crawford, H. L. [Lawrence Berkeley National Laboratory (LBNL); Doering, D. [Lawrence Berkeley National Laboratory (LBNL); Fallon, P. [Lawrence Berkeley National Laboratory (LBNL); Lionberger, C. [Lawrence Berkeley National Laboratory (LBNL); Loew, T. [Lawrence Berkeley National Laboratory (LBNL); Petri, M. [Lawrence Berkeley National Laboratory (LBNL); Stezelberger, T. [Lawrence Berkeley National Laboratory (LBNL); Zimmerman, S. [Lawrence Berkeley National Laboratory (LBNL); Radford, David C [ORNL; Lagergren, Karin B [ORNL; Weisshaar, D. [Michigan State University, East Lansing; Winkler, R. [Michigan State University, East Lansing; Glasmacher, T. [Michigan State University, East Lansing; Anderson, J. T, [Argonne National Laboratory (ANL); Beausang, C. W. [University of Richmond

2013-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "gamma-ray logging systems" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


421

SWIFT PANCHROMATIC OBSERVATIONS OF THE BRIGHT GAMMA-RAY BURST GRB 050525a A. J. Blustin,1  

E-Print Network (OSTI)

SWIFT PANCHROMATIC OBSERVATIONS OF THE BRIGHT GAMMA-RAY BURST GRB 050525a A. J. Blustin,1 D. Band,2 ABSTRACT The bright gamma-ray burst GRB 050525a has been detected with the Swift observatory, providing. This jet break time combined with the total gamma-ray energy of the burst constrains the opening angle

Zhang, Bing

422

ON THE KINETIC ENERGY AND RADIATIVE EFFICIENCY OF GAMMA-RAY BURSTS Nicole M. Lloyd-Ronning1  

E-Print Network (OSTI)

ON THE KINETIC ENERGY AND RADIATIVE EFFICIENCY OF GAMMA-RAY BURSTS Nicole M. Lloyd-Ronning1 of 17 gamma-ray bursts (GRBs) during the afterglow phase and ac- counting for radiative losses, we the implications of these results for the GRB radiation and jet models. Subject headinggs: gamma rays: bursts

Zhang, Bing

423

Gehrels_Answers 311.pdf Student questions: Neil Gehrels colloquium on "Gamma Ray Bursts and the Birth of Black  

E-Print Network (OSTI)

gamma repeaters, or gamma-ray bursts for which optical or ra- dio counterparts are found. In its first of HETE, the two principal GRB detectors close to Earth were the BeppoSAX Gamma- Ray Burst Moni- tor (GRBM aboard HETE-II has been successfully integrated into the Third Interplanetary Network (IPN) of gamma-ray

Rhoads, James

424

The gamma-ray burst monitor for Lobster-ISS L. Amati a,*, F. Frontera a,b  

E-Print Network (OSTI)

The gamma-ray burst monitor for Lobster-ISS L. Amati a,*, F. Frontera a,b , N. Auricchio a , E telescope is flanked by a Gamma Ray Burst Monitor, with the minimum requirement of recognizing true GRBs. Published by Elsevier Ltd. All rights reserved. Keywords: Gamma-rays: bursts; X-rays: transients

Bogliolo, Alessandro

425

A Gamma-Ray Burst Bibliography, 1973-2001 UC Berkeley Space Sciences Laboratory, Berkeley, CA 94720-7450  

E-Print Network (OSTI)

A Gamma-Ray Burst Bibliography, 1973-2001 K. Hurley UC Berkeley Space Sciences Laboratory, Berkeley, CA 94720-7450 Abstract. On the average, 1.5 new publications on cosmic gamma-ray bursts enter have been tracking the gamma-ray burst literature for about the past twenty-one years, keeping

California at Berkeley, University of

426

30TH INTERNATIONAL COSMIC RAY CONFERENCE Search for Gamma Ray Bursts using the single particle technique at the Pierre Auger  

E-Print Network (OSTI)

30TH INTERNATIONAL COSMIC RAY CONFERENCE Search for Gamma Ray Bursts using the single particle by satellites. Introduction Since their discovery at the end of the 60s[1], Gamma Ray Bursts (GRB) have been of high in- terest to astrophysics. A GRB is characterised by a sudden emission of gamma rays during

Hörandel, Jörg R.

427

Title of Dissertation: A Search for Short Duration Very High Energy Emission from Gamma-Ray Bursts  

E-Print Network (OSTI)

of GRBs. #12;A Search for Short Duration Very High Energy Emission from Gamma-Ray Bursts by David Noyes Gamma-Ray Bursts 1 1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 . . . . . . . . . . . . . . . . . . . . . . . . . . 60 3 The Gamma-Ray Burst Search 64 3.1 Introduction

California at Santa Cruz, University of

428

Magnetic Fields in Gamma-Ray Bursts: A Short Racah Institute for Physics, The Hebrew University, Jerusalem, 91904 Israel  

E-Print Network (OSTI)

Magnetic Fields in Gamma-Ray Bursts: A Short Overview Tsvi Piran Racah Institute for Physics Abstract. Magnetic fields play a crucial role in the physics of Gamma-Ray Bursts (GRBs). Strong thirty years, after the discovery of Gamma-Ray bursts (GRBs) we have now a reasonable GRB model

Jensen, Grant J.

429

JET BREAKS IN SHORT GAMMA-RAY BURSTS. I. THE UNCOLLIMATED AFTERGLOW OF GRB 050724 Dirk Grupe,1  

E-Print Network (OSTI)

JET BREAKS IN SHORT GAMMA-RAY BURSTS. I. THE UNCOLLIMATED AFTERGLOW OF GRB 050724 Dirk Grupe,1 the results of the Chandra observations of the Swift-discovered short gamma-ray burst GRB 050724. Chandra corrected energy of GRB 050724 is at least 4 ; 1049 ergs. Subject headinggs: gamma rays: bursts -- X-rays

Zhang, Bing

430

79Fermi Observatory Measures the Lumps in Space An artistic impression of two gamma-ray photons  

E-Print Network (OSTI)

explored to date. As the gamma-rays travel through space, the shortest-wavelength gamma-rays take? Problem 3 ­ The Fermi Telescope measured a gamma-ray pulse from a distant object located 10 billion light from a distant object located 10 billion light years from Earth. The time delay was no more than 0

431

Logs / Meeting Minutes Index  

NLE Websites -- All DOE Office Websites (Extended Search)

Logs / Meeting Minutes Logs / Meeting Minutes This page supplies links to the various logs and meeting minutes that are pertinent to the UES Group. FC Shift Log An ORACLE database tool used by the Floor Coordinators to record events that occur on the Experiment Hall Floor. FC Shift Log (Pubic View) Members of the APS Computer Network can use this link to view the FC Shift Log. MCR Shift Log An ORACLE database tool used by the MCR Operators to record events that occur relating to the operation of the Accelerating Systems. MCR Operator Message History The MCR Operator message for the past 72 hours are recorded for reference. UES Meeting Minutes The weekly User ESH Support group meeting minutes are recorded for reference. Also included are AOD-EOS and AOD-EFO meeting minutes. APS Radiation Safety PnP Committee Minutes

432

Database of prompt gamma rays from slow neutron capture forelemental analysis  

Science Conference Proceedings (OSTI)

The increasing importance of Prompt Gamma-ray ActivationAnalysis (PGAA) in a broad range of applications is evident, and has beenemphasized at many meetings related to this topic (e.g., TechnicalConsultants' Meeting, Use of neutron beams for low- andmedium-fluxresearch reactors: radiography and materialscharacterizations, IAEA Vienna, 4-7 May 1993, IAEA-TECDOC-837, 1993).Furthermore, an Advisory Group Meeting (AGM) for the Coordination of theNuclear Structure and Decay Data Evaluators Network has stated that thereis a need for a complete and consistent library of cold- and thermalneutron capture gammaray and cross-section data (AGM held at Budapest,14-18 October 1996, INDC(NDS)-363); this AGM also recommended theorganization of an IAEA CRP on the subject. The International NuclearData Committee (INDC) is the primary advisory body to the IAEA NuclearData Section on their nuclear data programmes. At a biennial meeting in1997, the INDC strongly recommended that the Nuclear Data Section supportnew measurements andupdate the database on Neutron-induced PromptGamma-ray Activation Analysis (21st INDC meeting, INDC/P(97)-20). As aconsequence of the various recommendations, a CRP on "Development of aDatabase for Prompt Gamma-ray Neutron Activation Analysis (PGAA)" wasinitiated in 1999. Prior to this project, several consultants had definedthe scope, objectives and tasks, as approved subsequently by the IAEA.Each CRP participant assumed responsibility for the execution of specifictasks. The results of their and other research work were discussed andapproved by the participants in research co-ordination meetings (seeSummary reports: INDC(NDS)-411, 2000; INDC(NDS)-424, 2001; andINDC(NDS)-443, 200). PGAA is a non-destructive radioanalytical method,capable of rapid or simultaneous "in-situ" multi-element analyses acrossthe entire Periodic Table, from hydrogen to uranium. However, inaccurateand incomplete data were a significant hindrance in the qualitative andquantitative analysis of complicated capture-gamma spectra by means ofPGAA. Therefore, the main goal of the CRP was to improve the quality andquantity of the required data in order to make possible the reliableapplication of PGAA in fields such as materials science, chemistry,geology, mining, archaeology, environment, food analysis and medicine.This aim wasachieved thanks to the dedicated work and effort of theparticipants. The CD-ROM included with this publication contains thedatabase, the retrieval system, the three CRM reports, and otherimportant electronic documents related to the CRP. The IAEA wishes tothanks all CRP participants who contributed to the success of the CRP andthe formulation of this publication. Special thanks are due to R.B.Firestone for his leading roll in the development of this CRP and hiscomprehensive compilation, analysis and provision of the adopteddatabase, and to V. Zerkin for the software developments associatedwiththe retrieval system. An essential component of this data compilation isthe extensive sets of new measurements of capture gamma-ray energies andintensities undertaken at Budapest by Zs. Revay under the direction ofG.L. Molnar. The extensive participation and assistance of H.D. Choi isalso greatly appreciated. Other participants inthis CRP were: R.M.Lindstrom, S.M. Mughabghab, A.V.R. Reddy, V.H. Tan and C.M. Zhou. Thanksare also due to S.C. Frankle and M.A. Lone for their active participationas consultants at some of the meetings. Finally, the participants wish tothank R. Paviotti-Corcuera (Nuclear Data Section, Division of Physicaland Chemical Sciences), who was the IAEA responsible officer for the CRP,this publication and the resulting database. The participants aregrateful to D.L. Muir and A.L. Nichols, successive Heads of the NuclearData Section, for their active and enthusiastic encouragement infurthering the work of the CRP.

Firestone, R.B.; Choi, H.D.; Lindstrom, R.M.; Molnar, G.L.; Mughabghab, S.F.; Paviotti-Corcuera, R.; Revay, Zs; Trkov, A.; Zhou,C.M.; Zerkin, V.

2004-12-31T23:59:59.000Z

433

Relativistic Conic Beams and Spatial Distribution of Gamma-Ray Bursts  

E-Print Network (OSTI)

We study the statistics of gamma-ray bursts, assuming that gamma-ray bursts are cosmological and they are beamed in the form of a conical jet with a large bulk Lorentz factor $\\sim 100$. In such a conic beam, the relativistic ejecta may have a spatial variation in the bulk Lorentz factor and the density distribution of gamma-ray emitting jet material. An apparent luminosity function arises because the axis of the cone is randomly oriented with respect to the observer's line of sight. The width and the shape of the luminosity function are determined by the ratio of the beam opening angle of the conical jet to the inverse of the bulk Lorentz factor, when the bulk Lorentz factor and the jet material density is uniform on the photon emitting jet surface. We calculate effects of spatial variation of the Lorentz factor and the spatial density fluctuations within the cone on the luminosity function and the statistics of gamma-ray bursts. In particular, we focus on the redshift distribution of the observed gamma-ray bursts. The maximum distance to and the average redshift of the gamma-ray bursts are strongly affected by the beaming-induced luminosity function. The bursts with the angle-dependent Lorentz factor which peaks at the center of the cone have substantially higher average gamma-ray burst redshifts. When both the jet material density and the Lorentz factor are inhomogeneous in the conical beam, the average redshift of the bursts could be 5 times higher than that of the case in which relativistic jet is completely homogeneous and structureless. Even the simplest models for the gamma-ray burst jets and their apparent luminosity distributions have a significant effect on the redshift distribution of the gamma-ray bursts.

Heon-Young Chang; Insu Yi

2000-05-15T23:59:59.000Z

434

On the mechanism of prompt emission of gamma-ray bursts  

E-Print Network (OSTI)

We propose a model in which prompt gamma emission of gamma-ray bursts is the synchrotron radiation of electron-positron plasma in the ordered magnetic field in the direct vicinity of horizon of a young black hole formed in the core collapse of a massive star. This mechanism can naturally explain high degree of polarization of the gamma-ray flux and hard low energy photon spectral index. Interaction of gamma-quanta with ambient matter provides a mechanism of formation of relativistic ejecta which are responsible for the gamma-ray burst afterglows.

Andrey Neronov

2003-11-05T23:59:59.000Z

435

TeV Scale Quantum Gravity and Mirror Supernovae as Sources of Gamma Ray Bursts  

E-Print Network (OSTI)

Mirror matter models have been suggested recently as an explanation of neutrino puzzles and microlensing anomalies. We show that mirror supernovae can be a copious source of energetic gamma rays if one assumes that the quantum gravity scale is in the TeV range. We show that under certain assumptions plausible in the mirror models, the gamma energies could be degraded to the 10 MeV range (and perhaps even further) so as to provide an explanation of observed gamma ray bursts. This mechanism for the origin of the gamma ray bursts has the advantage that it neatly avoids the ``baryon load problem''.

R. N. Mohapatra; S. Nussinov; V. L. Teplitz

1999-09-22T23:59:59.000Z

436

The Search for Dark Matter with the Fermi Gamma Ray Space Telescope  

SciTech Connect

The Fermi Gamma-Ray Space Telescope has been scanning the gamma ray sky since it was launched by NASA in June 2008 and has a mission lifetime goal of 10 years. Largely due to our particle physics heritage, one of the main physics topics being studied by the Fermi LAT Collaboration is the search for dark matter via indirect detection. My talk will review the progress of these studies, something on how the LAT detector enables them, and expectations for the future. I will discuss both gamma-ray and (electron + positron) searches for dark matter, and some resulting theoretical implications.

Bloom, Elliott (SLAC)

2011-03-30T23:59:59.000Z

437

Emission of Radio Waves in Gamma Ray Bursts and Axionic Boson Stars  

E-Print Network (OSTI)

We point out that the bursts of photons with the energy of the axion mass may appear coincidentally with gamma ray bursts if the gamma ray bursts are caused by collisions between neutron stars and axionic boson stars. In this mechanism, jets are formed in the collisions with large Lorentz factors $\\geq 10^2$. We explain qualitatively time-dependent complex structures of gamma ray bursts as well as the large energy problem. Therefore, with detection of the monochromatic photons we can test the model and determine the axion mass.

Aiichi Iwazaki

1999-08-26T23:59:59.000Z

438

Recent results from the Milagro TeV gamma-ray observatory  

E-Print Network (OSTI)

Milagro is a gamma-ray observatory employing a water Cherenkov detector to observe extensive air showers produced by high-energy particles impacting in the Earth's atmosphere. We discuss the first detection of TeV gamma-rays from the Galactic plane and report the detection of an extended TeV source coincident with the EGRET source 3EG J0520+2556, and the observation of TeV emission from the Cygnus region of our Galaxy. We also summarize the status of our search for Very High Energy (VHE) emission from satellite-triggered Gamma Ray Bursts (GRBs) and discuss plans for the next generation water Cherenkov detector.

Parkinson, P M S

2005-01-01T23:59:59.000Z

439

Toward Ultra Short Gamma Ray Burst Ground Based Detection, SGARFACE status  

E-Print Network (OSTI)

We present the status and motivation of the Short GAmma Ray Front Air Cherenkov Experiment (SGARFACE) which will be operated parallel to standard Very High Energy gamma-ray observations using the Whipple 10m telescope. SGARFACE is sensitive to 100MeV-10GeV gamma-ray bursts with durations ranging from 100ns to 100us providing a fluence sensitivity as low as few $\\rm 1E-9 erg/cm^2. Preliminary data taking started in November 2002.

Stephan LeBohec; Frank Krennrich; Gary Sleege

2002-12-11T23:59:59.000Z

440

Sensitivity of the FERMI Detectors to Gamma-Ray Bursts from Evaporating Primordial Black Holes (PBHs)  

E-Print Network (OSTI)

Primordial Black Holes (PBHs), which may have been created in the early Universe, are predicted to be detectable by their Hawking radiation. The Fermi Gamma-ray Space Telescope observatory offers increased sensitivity to the gamma-ray bursts produced by PBHs with an initial mass of $\\sim 5\\times 10^{14}$ g expiring today. PBHs are candidate progenitors of unidentified Gamma-Ray Bursts (GRBs) that lack X-ray afterglow. We propose spectral lag, which is the temporal delay between the high and low energy pulses, as an efficient method to identify PBH evaporation events with the Fermi Large Area Telescope (LAT).

T. N. Ukwatta; Jane H. MacGibbon; W. C. Parke; K. S. Dhuga; S. Rhodes; A. Eskandarian; N. Gehrels; L. Maximon; D. C. Morris

2010-03-23T23:59:59.000Z

Note: This page contains sample records for the topic "gamma-ray logging systems" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


441

The polarized Gamma-Ray Burst GRB 061122  

E-Print Network (OSTI)

We report on the polarization measure, obtained with IBIS on board INTEGRAL, of the prompt emission of GRB 061122. Over an 8 s interval containing the brightest part of the Gamma-Ray Burst we put a lower limit on its polarization fraction of 60% at 68% c.l. and of 33% at 90% c.l. on the 250-800 keV energy range. We performed late time optical and near infra-red imaging observations of the GRB field using the Telescopio Nazionale Galileo (TNG), and the Canada-France-Hawaii Telescope (CFHT). Our multi-band (ugrizYJHK) photometry allowed us to identify the host galaxy of GRB 061122 and to build its SED. Using a photometric redshift code we fitted these data, and derived the basic properties of the galaxy, including its type and redshift, that we could constrain to the interval [0.57, 2.10] at a 90% c.l., with a best fit value of z=1.33. The polarization measurement in different energy bands, together with the distance determination, allowed us to put the most stringent limit (xi < 3.4x10-16) to date to a poss...

Gotz, D; Fernandez-Soto, A; Laurent, P; Bosnjak, Z

2013-01-01T23:59:59.000Z

442

Neutrinos and Nucleosynthesis in Gamma-Ray Burst Accretion Disks  

E-Print Network (OSTI)

We calculate the nuclear composition of matter in accretion disks surrounding stellar mass black holes as are thought to accompany gamma-ray bursts (GRBs). We follow a mass element in the accretion disk starting at the point of nuclear dissociation and calculate the evolution of the electron fraction due to electron, positron, electron neutrino and electron antineutrino captures. We find that the neutronization of the disk material by electron capture can be reversed by neutrino interactions in the inner regions of disks with accretion rates of 1 M_solar/s and higher. For these cases the inner disk regions are optically thick to neutrinos, and so to estimate the emitted neutrino fluxes we find the surface of last scattering for the neutrinos (the equivalent of the proto-neutron star neutrinosphere) for each optically thick disk model. We also estimate the influence of neutrino interactions on the neutron-to-proton ratio in outflows from GRB accretion disks, and find it can be significant even when the disk is optically thin to neutrinos.

R. Surman; G. C. McLaughlin

2003-07-31T23:59:59.000Z

443

Thermal Emission in Gamma-Ray Burst Afterglows  

E-Print Network (OSTI)

We study thermal emission from circumstellar structures heated by gamma-ray burst (GRB) radiation and ejecta and calculate its contribution to GRB optical and X-ray afterglows using the modified radiation hydro-code small STELLA. It is shown that thermal emission originating in heated dense shells around the GRB progenitor star can reproduce X-ray plateaus (like observed in GRB 050904, 070110) as well as deviations from a power law fading observed in optical afterglows of some GRBs (e.g. 020124, 030328, 030429X, 050904). Thermal radiation pressure in the heated circumburst shell dominates the gas pressure, producing rapid expansion of matter similar to supenova-like explosions close to opacity or radiation flux density jumps in the circumburst medium. This phenomenon can be responsible for so-called supernova bumps in optical afterglows of several GRBs. Such a `quasi-supernova' suggests interpretation of the GRB-SN connection which does not directly involve the explosion of the GRB progenitor star.

Badjin, D A

2013-01-01T23:59:59.000Z

444

ARE T TAURI STARS GAMMA-RAY EMITTERS?  

Science Conference Proceedings (OSTI)

T Tauri stars are young, low-mass, pre-main-sequence stars surrounded by an accretion disk. These objects present strong magnetic activity and powerful magnetic reconnection events. Strong shocks are likely associated with fast reconnection in the stellar magnetosphere. Such shocks can accelerate particles up to relativistic energies. We aim at developing a simple model to calculate the radiation produced by non-thermal relativistic particles in the environment of T Tauri stars. We want to establish whether this emission is detectable at high energies with the available or forthcoming {gamma}-ray telescopes. We assume that particles (protons and electrons) pre-accelerated in reconnection events are accelerated at shocks through the Fermi mechanism and we study the high-energy emission produced by the dominant radiative processes. We calculate the spectral energy distribution of T Tauri stars up to high energies and we compare the integrated flux obtained with that from a specific Fermi source, 1FGL J1625.8-2429c, that we tentatively associate with this kind of young stellar object. We suggest that under reasonable general conditions nearby T Tauri stars might be detected at high energies and be responsible for some unidentified Fermi sources on the Galactic plane.

Victoria del Valle, Maria; Romero, Gustavo E. [Instituto Argentino de Radioastronomia (IAR), CCT La Plata (CONICET), C.C.5, 1894 Villa Elisa, Buenos Aires (Argentina); Luque-Escamilla, Pedro Luis [Departamento de Ingenieria Mecanica y Minera, Escuela Politecnica Superior de Jaen, Universidad de Jaen, Campus Las Lagunillas s/n, A3, 23071 Jaen (Spain); Marti, Josep; Sanchez-Sutil, Juan Ramon [Departamento de Fisica, Escuela Politecnica Superior de Jaen, Universidad de Jaen, Campus Las Lagunillas s/n, A3, 23071 Jaen (Spain)

2011-09-01T23:59:59.000Z

445

The Energy Distribution of Gamma-Ray Bursts  

E-Print Network (OSTI)

The distribution of the apparent total energy emitted by a gamma-ray burst reflects not only the distribution of the energy actually released by the burst engine, but also the distribution of beaming angles. Using the observed energy fluences, the detection thresholds and burst redshifts for three burst samples, I calculate the best-fit parameters for lognormal and power-law distributions of the apparent total energy. Two of the samples include a small number of bursts with spectroscopic redshifts, while the third sample has 220 bursts with redshifts determined by the proposed variability-luminosity correlation. I find different sets of parameter values for the three burst samples. The Bayesian odds ratio cannot distinguish between the two model distribution functions for the two smaller burst samples with spectroscopic redshifts, but does favor the lognormal distribution for the larger sample with variability-derived redshifts. The data do not rule out a distribution with a low energy tail which is currently unobservable. I find that neglecting the burst detection threshold biases the fitted distribution to be narrower with a higher average value than the true distribution; this demonstrates the importance of determining and reporting the effective detection threshold for bursts in a sample.

David L. Band

2001-05-15T23:59:59.000Z

446

REDSHIFT CATALOG FOR SWIFT LONG GAMMA-RAY BURSTS  

Science Conference Proceedings (OSTI)

We present a catalog of the redshifts for most long-duration gamma-ray bursts (GRBs) by Swift from 2004 December 20 to 2008 July 23 (258 bursts in total). All available information is collected, including spectroscopic redshifts, photometric redshift limits, and redshifts calculated from various luminosity relations. Error bars for the redshifts derived from the luminosity relations are asymmetric, with tails extended to the high-redshift end, and this effect is evaluated by looking at the 30% of Swift bursts with spectroscopic redshifts. A simulation is performed to eliminate this asymmetric effect, and the resultant redshift distribution is deconvolved. We test and confirm this simulation on the sample of bursts with known spectroscopic redshifts and then apply it to the 70% of Swift bursts that do not have spectroscopic measures. A final intrinsic redshift distribution is then made for almost all Swift bursts, and the efficiency of the spectroscopic detections is evaluated. The efficiency of spectroscopic redshifts varies from near unity at low redshift to 0.5 at z = 1, to near 0.3 at z = 4, and to 0.1 at z = 6. We also find that the fraction of GRBs with z>5 is {approx}10%, and this fraction is compared with simulations from a cosmological model.

Xiao Limin; Schaefer, Bradley E., E-mail: lxiao1@lsu.edu [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803 (United States)

2011-04-20T23:59:59.000Z

447

The Molecular Hydrogen Deficit in Gamma-Ray Burst Afterglows  

E-Print Network (OSTI)

Recent analysis of five gamma-ray burst (GRB) afterglow spectra reveal the absence of molecular hydrogen absorption lines, a surprising result in light of their large neutral hydrogen column densities and the detection of H$_2$ in similar, more local star-forming regions like 30 Doradus in the Large Magellanic Cloud (LMC). Observational evidence further indicates that the bulk of the neutral hydrogen column in these sight lines lies 100 pc beyond the progenitor and that H$_2$ was absent prior to the burst, suggesting that direct flux from the star, FUV background fields, or both suppressed its formation. We present one-dimensional radiation hydrodynamical models of GRB host galaxy environments, including self-consistent radiative transfer of both ionizing and Lyman-Werner photons, nine-species primordial chemistry with dust formation of H$_2$, and dust extinction of UV photons. We find that a single GRB progenitor is sufficient to ionize neutral hydrogen to distances of 50 - 100 pc but that a galactic Lyman-Werner background is required to dissociate the molecular hydrogen in the ambient ISM. Intensities of 0.1 - 100 times the Galactic mean are necessary to destroy H$_2$ in the cloud, depending on its density and metallicity. The minimum radii at which neutral hydrogen will be found in afterglow spectra is insensitive to the mass of the progenitor or the initial mass function (IMF) of its cluster, if present.

Daniel Whalen; Jason X. Prochaska; Alexander Heger; Jason Tumlinson

2008-02-06T23:59:59.000Z

448

DIFFUSE PeV NEUTRINOS FROM GAMMA-RAY BURSTS  

SciTech Connect

The IceCube Collaboration recently reported the potential detection of two cascade neutrino events in the energy range 1-10 PeV. We study the possibility that these PeV neutrinos are produced by gamma-ray bursts (GRBs), paying special attention to the contribution by untriggered GRBs that elude detection due to their low photon flux. Based on the luminosity function, rate distribution with redshift and spectral properties of GRBs, we generate, using a Monte Carlo simulation, a GRB sample that reproduces the observed fluence distribution of Fermi/GBM GRBs and an accompanying sample of untriggered GRBs simultaneously. The neutrino flux of every individual GRB is calculated in the standard internal shock scenario, so that the accumulative flux of the whole samples can be obtained. We find that the neutrino flux in PeV energies produced by untriggered GRBs is about two times higher than that produced by the triggered ones. Considering the existing IceCube limit on the neutrino flux of triggered GRBs, we find that the total flux of triggered and untriggered GRBs can reach at most a level of {approx}10{sup -9} GeV cm{sup -2} s{sup -1} sr{sup -1}, which is insufficient to account for the reported two PeV neutrinos. Possible contributions to diffuse neutrinos by low-luminosity GRBs and the earliest population of GRBs are also discussed.

Liu, Ruo-Yu; Wang, Xiang-Yu [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China)] [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China)

2013-04-01T23:59:59.000Z

449

MAGNETIZATION DEGREE OF GAMMA-RAY BURST FIREBALLS: NUMERICAL STUDY  

Science Conference Proceedings (OSTI)

The relative strength between forward and reverse shock emission in early gamma-ray burst (GRB) afterglow reflects that of magnetic energy densities in the two shock regions. We numerically show that with the current standard treatment, the fireball magnetization is underestimated by up to two orders of magnitude. This discrepancy is especially large in the sub-relativistic reverse shock regime (i.e., the thin shell and intermediate regime), where most optical flashes were detected. We provide new analytic estimates of the reverse shock emission based on a better shock approximation, which well describe numerical results in the intermediate regime. We show that the reverse shock temperature at the onset of afterglow is constant, ( {Gamma}-bar{sub d}-1){approx}8 Multiplication-Sign 10{sup -2}, when the dimensionless parameter {xi}{sub 0} is more than several. Our approach is applied to case studies of GRB 990123 and 090102, and we find that magnetic fields in the fireballs are even stronger than previously believed. However, these events are still likely to be due to a baryonic jet with {sigma} {approx} 10{sup -3} for GRB 990123 and {approx}3 Multiplication-Sign 10{sup -4} to 3 for GRB 090102.

Harrison, Richard; Kobayashi, Shiho, E-mail: R.M.Harrison@2006.ljmu.ac.uk [Astrophysics Research Institute, Liverpool John Moores University, Liverpool, L3 5RF (United Kingdom)

2013-08-01T23:59:59.000Z

450

Diversity of the Supernova - Gamma-Ray Burst Connection  

E-Print Network (OSTI)

The connection between the long Gamma Ray Bursts (GRBs) and Type Ic Supernovae (SNe) has revealed interesting diversity. We review the following types of the GRB-SN connection. (1) GRB-SNe: The three SNe all explode with energies much larger than those of typical SNe, thus being called Hypernovae (HNe). They are massive enough for forming black holes. (2) Non-GRB HNe/SNe: Some HNe are not associated with GRBs. (3) XRF-SN: SN 2006aj associated with X-Ray Flash 060218 is dimmer than GRB-SNe and has very weak oxygen lines. Its progenitor mass is estimated to be small enough to form a neutron star rather than a black hole. (4) Non-SN GRB: Two nearby long GRBs were not associated SNe. Such ``dark HNe'' have been predicted in this talk (i.e., just before the discoveries) in order to explain the origin of C-rich (hyper) metal-poor stars. This would be an important confirmation of the Hypernova-First Star connection. We will show our attempt to explain the diversity in a unified manner with the jet-induced explosion model.

K. Nomoto; N. Tominaga; M. Tanaka; K. Maeda; T. Suzuki; J. S. Deng; P. A. Mazzali

2007-02-19T23:59:59.000Z

451

Robust Limits on Lorentz Violation from Gamma-Ray Bursts  

E-Print Network (OSTI)

We constrain the possibility of a non-trivial refractive index in free space corresponding to an energy-dependent velocity of light: c(E) \\simeq c_0 (1 - E/M), where M is a mass scale that might represent effect of quantum-gravitational space-time foam, using the arrival times of sharp features observed in the intensities of radiation with different energies from a large sample of gamma-ray bursters (GRBs) with known redshifts. We use wavelet techniques to identify genuine features, which we confirm in simulations with artificial added noise. Using the weighted averages of the time-lags calculated using correlated features in all the GRB light curves, we find a systematic tendency for more energetic photons to arrive earlier. However, there is a very strong correlation between the parameters characterizing an intrinsic time-lag at the source and a distance-dependent propagation effect. Moreover, the significance of the earlier arrival times is less evident for a subsample of more robust spectral structures. Allowing for intrinsic stochastic time-lags in these features, we establish a statistically robust lower limit: M > 0.9x10^{16} GeV on the scale of violation of Lorentz invariance.

John Ellis; Nick E. Mavromatos; Dimitri V. Nanopoulos; Alexander S. Sakharov; Edward K. G. Sarkisyan

2005-10-06T23:59:59.000Z

452

Outage Log  

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453

Detecting special nuclear materials in suspect containers using high-energy gamma rays emitted by fission products  

DOE Patents (OSTI)

A method and a system for detecting the presence of special nuclear materials in a suspect container. The system and its method include irradiating the suspect container with a beam of neutrons, so as to induce a thermal fission in a portion of the special nuclear materials, detecting the gamma rays that are emitted from the fission products formed by the thermal fission, to produce a detector signal, comparing the detector signal with a threshold value to form a comparison, and detecting the presence of the special nuclear materials using the comparison.

Norman, Eric B. (Oakland, CA); Prussin, Stanley G. (Kensington, CA)

2009-01-06T23:59:59.000Z

454

Detecting special nuclear materials in suspect containers using high-energy gamma rays emitted by fission products  

DOE Patents (OSTI)

A method and a system for detecting the presence of special nuclear materials in a suspect container. The system and its method include irradiating the suspect container with a beam of neutrons, so as to induce a thermal fission in a portion of the special nuclear materials, detecting the gamma rays that are emitted from the fission products formed by the thermal fission, to produce a detector signal, comparing the detector signal with a threshold value to form a comparison, and detecting the presence of the special nuclear materials using the comparison.

Norman, Eric B. (Oakland, CA); Prussin, Stanley G. (Kensington, CA)

2009-01-27T23:59:59.000Z

455

Detecting special nuclear materials in suspect containers using high-energy gamma rays emitted by fission products  

DOE Patents (OSTI)

A method and a system for detecting the presence of special nuclear materials in a suspect container. The system and its method include irradiating the suspect container with a beam of neutrons, so as to induce a thermal fission in a portion of the special nuclear materials, detecting the gamma rays that are emitted from the fission products formed by the thermal fission, to produce a detector signal, comparing the detector signal with a threshold value to form a comparison, and detecting the presence of the special nuclear materials using the comparison.

Norman, Eric B [Oakland, CA; Prussin, Stanley G [Kensington, CA

2009-05-05T23:59:59.000Z

456

HYPERACCRETING BLACK HOLE AS GAMMA-RAY BURST CENTRAL ENGINE. I. BARYON LOADING IN GAMMA-RAY BURST JETS  

SciTech Connect

A hyperaccreting stellar-mass black hole has been long speculated as the best candidate for the central engine of gamma-ray bursts (GRBs). Recent rich observations of GRBs by space missions such as Swift and Fermi pose new constraints on GRB central engine models. In this paper, we study the baryon-loading processes of a GRB jet launched from a black hole central engine. We consider a relativistic jet powered by {nu} {nu}-bar -annihilation or by the Blandford-Znajek (BZ) mechanism. We consider baryon loading from a neutrino-driven wind launched from a neutrino-cooling-dominated accretion flow. For a magnetically dominated BZ jet, we consider neutron drifting from the magnetic wall surrounding the jet and subsequent positron capture and proton-neutron inelastic collisions. The minimum baryon loads in both types of jet are calculated. We find that in both cases a more luminous jet tends to be more baryon poor. A neutrino-driven ''fireball'' is typically ''dirtier'' than a magnetically dominated jet, while a magnetically dominated jet can be much cleaner. Both models have the right scaling to interpret the empirical {Gamma}-L{sub iso} relation discovered recently. Since some neutrino-driven jets have too much baryon loading as compared with the data, we suggest that at least a good fraction of GRBs should have a magnetically dominated central engine.

Lei Weihua [School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); Zhang Bing [Department of Physics and Astronomy, University of Nevada Las Vegas, 4505 Maryland Parkway, Box 454002, Las Vegas, NV 89154-4002 (United States); Liang Enwei, E-mail: leiwh@hust.edu.cn, E-mail: zhang@physics.unlv.edu [Department of Physics and GXU-NAOC Center for Astrophysics and Space Sciences, Guangxi University, Nanning 530004 (China)

2013-03-10T23:59:59.000Z

457

Models for the circumstellar medium of long gamma-ray burst progenitor candidates.  

E-Print Network (OSTI)

??Long gamma-ray bursts are highly energetic events that are thought to occur when certain massive stars, that end their lives as Wolf-Rayet stars, collapse at… (more)

Marle, A.J. van

2006-01-01T23:59:59.000Z

458

Hybrid model of GeV-TeV gamma ray emission from Galactic Center  

E-Print Network (OSTI)

The observations of high energy $\\gamma$-ray emission from the Galactic center (GC) by HESS, and recently by Fermi, suggest the cosmic ray acceleration in the GC and possibly around the supermassive black hole. In this work we propose a lepton-hadron hybrid model to explain simultaneously the GeV-TeV $\\gamma$-ray emission. Both electrons and hadronic cosmic rays were accelerated during the past activity of the GC. Then these particles would diffuse outwards and interact with the interstellar gas and background radiation field. The collisions between hadronic cosmic rays with gas is responsible to the TeV $\\gamma$-ray emission detected by HESS. With fast cooling in the strong radiation field, the electrons would cool down and radiate GeV photons through inverse Compton scattering off the soft background photons. This scenario provides a natural explanation of the observed GeV-TeV spectral shape of $\\gamma$-rays.

Yi-Qing Guo; Qiang Yuan; Cheng Liu; Ai-Feng Li

2013-03-26T23:59:59.000Z

459

In the OSTI Collections: Gamma-Ray Bursts | OSTI, US Dept of Energy, Office  

Office of Scientific and Technical Information (OSTI)

Gamma-Ray Bursts Gamma-Ray Bursts The Fermi Gamma-ray Space Telescope and its first lessons Seeing indirectly by shining light through light Gamma-ray bursters The Large Synoptic Survey Telescope An emerging picture References Research Organizations Instrument Websites Reports Available through OSTI's SciTech Connect Additional Reference The night sky, as our unaided eyes present it to us, obviously contains the sun, the moon, thousands of stars, a few planets, a milky band of light that stretches from horizon to horizon, the occasional meteor or meteor shower, and sometimes a comet. A few centuries of examination with eyes aided by many kinds of instruments have revealed more and more of the nature of these objects-for example, that the planets are more or less like the Earth, orbiting the sun, with some planets having moons of various

460

An Attempt To Use Aerial Gamma-Ray Spectrometry Results In Petrochemical  

Open Energy Info (EERE)

Attempt To Use Aerial Gamma-Ray Spectrometry Results In Petrochemical Attempt To Use Aerial Gamma-Ray Spectrometry Results In Petrochemical Assessments Of The Volcanic And Plutonic Associations Of Central Anatolia (Turkey) Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Journal Article: An Attempt To Use Aerial Gamma-Ray Spectrometry Results In Petrochemical Assessments Of The Volcanic And Plutonic Associations Of Central Anatolia (Turkey) Details Activities (0) Areas (0) Regions (0) Abstract: Volcanic and magmatic rocks of Central Anatolia are fairly rich in radioelement concentrations. The aerial gamma-ray spectrometric survey data, gathered for the purpose of radioactive mineral exploration were utilized as an additional tool for the petrochemical classification of the volcanic and magmatics rocks and their environments. The survey data on

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461

New gamma-ray observatory begins operations at Sierra Negra volcano in the  

NLE Websites -- All DOE Office Websites (Extended Search)

New gamma-ray observatory begins operations New gamma-ray observatory begins operations New gamma-ray observatory begins operations at Sierra Negra volcano in the state of Puebla, Mexico The High-Altitude Water Cherenkov Gamma Ray Observatory has begun formal operations at its site in Mexico. August 21, 2013 The HAWC Observatory taken in August 2013 from the summit of Sierra Negra. The image has been digitally altered to show HAWC as it will appear when construction is complete in 2014. The 111 Cherenkov detectors currently installed (100 Cherenkov detectors in operation) are colored white and located in the upper right quadrant of the array. The HAWC Observatory taken in August 2013 from the summit of Sierra Negra. The image has been digitally altered to show HAWC as it will appear when construction is complete in 2014. The 111 Cherenkov detectors currently

462

A Blind Search for Bursts of Very High Energy Gamma Rays with Milagro.  

E-Print Network (OSTI)

??Milagro is a water-Cherenkov detector that observes the extended air showers produced by cosmic gamma rays of energies E>100GeV. The effective area of Milagro peaks… (more)

Vasileiou, Vlasios

2008-01-01T23:59:59.000Z