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Note: This page contains sample records for the topic "waha lone star" 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.


1

Lone Star Healthy Streams: Teaching best managment practices statewide  

E-Print Network [OSTI]

txH2O | pg. 22 Story by Leslie Lee The Lone Star Healthy Streams (LSHS) Program uses education to reduce the amount of bacteria entering Texas water bodies from livestock operations and feral hogs. This program, originally developed...

Lee, Leslie

2011-01-01T23:59:59.000Z

2

Lone Star Healthy Streams: Teaching best management practices statewide  

E-Print Network [OSTI]

txH2O | pg. 22 Story by Leslie Lee The Lone Star Healthy Streams (LSHS) Program uses education to reduce the amount of bacteria entering Texas water bodies from livestock operations and feral hogs. This program, originally developed...

Lee, Leslie

2010-01-01T23:59:59.000Z

3

Lone Star Healthy Streams: Keeping Texas streams clean  

E-Print Network [OSTI]

include BMPs identi#30;ed in Stage I. ?Stage II focuses on education,? said Jennifer Peterson, LSHS statewide coordinator. ?For each bacterial contributor, we created a manual and a presentation outlining BMPs that are operation- speci#30;c.? #31;e... that are available for them to reduce water quality problems. #31;e LSHS program is designed to educate landowners on these topics. 26 tx H2O Winter 2013 Lone Star Healthy Streams continued The practices listed in the Lone Star Health Streams manuals...

Boutwell, Kathryn S.

2013-01-01T23:59:59.000Z

4

Effective Lone Star program reduces unaccounted-for gas  

SciTech Connect (OSTI)

Lone Star's program for holding down its gas losses implements individual remedies for each of six broad categories of unaccounted-for gas: measurement at other than base conditions, meter inaccuracy, meter-reading errors, accounting mistakes, unmetered or unrecorded gas use, and leakage. Even though some of these remedies will not be fully effective for 2 more years, the program's first year of operation has reduced unaccounted-for gas volumes by 9.2%.

Wallace, J.E.

1982-04-01T23:59:59.000Z

5

Lone Star Reds: the Socialist Party and cotton tenancy in Texas, 1901-1917  

E-Print Network [OSTI]

ideal, the party of Eugene Debs seized on the strong Texas tradition of agrarian revolt to build a formidable, if short-lived, Socialist movement in the Lone Star State. There were Socialist newspapers, unions, rural encampments, and a Socialist...

Mellard, Jason Dean

2000-01-01T23:59:59.000Z

6

Clean Cities: Lone Star Clean Fuels Alliance (Central Texas) coalition  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr MayAtmospheric Optical Depth7-1D: Vegetation Proposed New SubstationClean Communities of Western New YorkGreater NewKentucky CleanLandLone

7

Policy Recommendations for Establishing the LoneSTAR Monitoring and Analysis Program  

E-Print Network [OSTI]

energy consumption analyzed?sometimes with monthly data and sometimes with 15-minute or hourly demand data. 6 The levels of monitoring and analysis recommended can be grouped in three categories: 1) Facility/whole building(s) utility data: These data... receiving retrofits 3) Improve retrofit selection in future rounds of the LoanSTAR Program - 4) Provide a detailed data base of energy use in commercial* buildings located in Texas The money for each retrofit financed from the LoanSTAR Program must...

Claridge, D. E.; O'Neal, D. L.; Turner, W. D.

1989-01-01T23:59:59.000Z

8

LoneSTAR Program: Maximizing Energy Efficiency while Protecting the Envrionment  

E-Print Network [OSTI]

Assessment Report (EAR) ? Utility Assessment Report (UAR) ? Systems Commissioning Report (in the case where the commissioning meets LoanSTAR payback requirements) ESL-KT-14-11-31 CATEE 2014: Clean Air Through Efficiency Conference, Dallas, Texas Nov. 18...Maximiz ing Energy Eff ic iency whi le Protect ing the Envi ronment LoanSTAR PROGRAM ESL-KT-14-11-31 CATEE 2014: Clean Air Through Efficiency Conference, Dallas, Texas Nov. 18-20 ? Executed 240 loans totaling $407,923,762.32 ? 93 loans to publ...

Trevino, E.

2014-01-01T23:59:59.000Z

9

Authigenic clay minerals in sandstones of the Delaware Mountain Group: Bell Canyon and Cherry Canyon Formations, Waha Field, West Texas  

E-Print Network [OSTI]

AUTHIGENIC CLAY MINERALS IN SANDSTONES OF THE DELAWARE MOUNTAIN GROUP: BELL CANYON AND CHERRY CANYON FORMATIONS, WAHA FIELD, WEST TEXAS A Thesis by SUZETTE DENISE WALLING Submitted to the Office of Graduate Studies of Texas A&M University... in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE December 1992 Major Subject: Geology AUTHIGENIC CLAY MINERALS IN SANDSTONES OF THE DELAWARE MOUNTAIN GROUP: BELL CANYON AND CHERRY CANYON FORMATIONS, WAHA FIELD, WEST TEXAS...

Walling, Suzette Denise

1992-01-01T23:59:59.000Z

10

Lone Star Healthy Streams Final Report  

E-Print Network [OSTI]

bacteria from grazing lands has been identified as a significant source of bacterial contamination in need of reductions to improve water quality. Development of best management practices to address these bacterial issues is critical to the success... of watershed restoration efforts. The effects of alternative water supplies and grazing management were evaluated to assess their effectiveness as best management practices (BMPs). Providing alternative water supplies for cattle reduced the time cattle spent...

Wagner, Kevin; Redmon, Larry

11

Lone Star Transmission LLC | Open Energy Information  

Open Energy Info (EERE)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home5b9fcbce19 No revision hasInformation Earth's Heat JumpInc Place:KeystoneSolarListLiveFuels Inc JumpLoess HillsIII Jump

12

Lone Star I (Q2) Wind Farm | Open Energy Information  

Open Energy Info (EERE)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home5b9fcbce19 No revision hasInformation Earth's Heat JumpInc Place:KeystoneSolarListLiveFuels Inc JumpLoess HillsI (4Q07)Q2)

13

Lone Star I (Q3) Wind Farm | Open Energy Information  

Open Energy Info (EERE)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home5b9fcbce19 No revision hasInformation Earth's Heat JumpInc Place:KeystoneSolarListLiveFuels Inc JumpLoess HillsI

14

Lone Star Wind Alliance LSWA | Open Energy Information  

Open Energy Info (EERE)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home5b9fcbce19 No revision hasInformation Earth's Heat JumpInc Place:KeystoneSolarListLiveFuels Inc JumpLoess HillsIII

15

Vortex Shedding on Hydrofoils Its dark and lonely down there...  

E-Print Network [OSTI]

Vortex Shedding on Hydrofoils Its dark and lonely down there... Improving marine vehicle an underwater vehicle moves, it displaces water, genera6ng a unique velocity that it can u6lize rather than fight those flows, saving energy and improving

16

Dead poets' society New England, the 1950s. Todd Anderson (Ethan Hawke), a lonely and painfully  

E-Print Network [OSTI]

Dead poets' society New England, the 1950s. Todd Anderson (Ethan Hawke), a lonely and painfully shy in it. After seeing that Mr. Keating listed "Dead Poets Society" as one of his activities at the school

Schenato, Luca

17

BAUCHE TALLIES LONE GOAL IN HUSKIE WIN By Nicole Betker, University of Saskatchewan Sports Information  

E-Print Network [OSTI]

BAUCHE TALLIES LONE GOAL IN HUSKIE WIN By Nicole Betker, University of Saskatchewan Sports Information SASKATOON, SK - University of Saskatchewan rookie Mitch Bauche tallied his first CIS goal in a 1 sides had numerous opportunities to score. Saskatchewan tallied 30 shots in the game, while UNBC had 16

Northern British Columbia, University of

18

"Climate Wise" in the Lone Star State: A Successful Partnership for Energy Efficiency in Austin, Texas  

E-Print Network [OSTI]

The City of Austin, Texas is forming partnerships with local companies to lower energy consumption and improve environmental performance within the industrial sector. As a local government participant in the federal Climate Wise program, Austin...

Allen, S. J.; Schare, S.

19

Energy Engineering Analysis (EEA) program for Lone Star Army Ammunition Plant, Texas. Executive summary. Final report  

SciTech Connect (OSTI)

The objective of this Energy Engineering Analysis (EEA) for LSAAP is threefold: Develop a systematic plan of projects which will result in reducing energy consumption. Consider renewable energy sources with the objective of establishing an orderly procedure for reducing use of non-renewable energy sources. Determine the feasibility of Total Energy (TE), Selective Energy (SE), and Central Heating Plant (CHP) concepts using alternative fuels. In essence, an assessment of the entire energy picture at LSAAP was undertaken. This report is a summary of that effort. LSAAP was originally built during 1941 and 1942 as a shell loading plant for the Army. After World War II, the facility was deactivated until 1951 when it was reactivated as a Government Owned, Contractor Operated (GOCO) facility. Day and Zimmerman was selected as the operator in 1951 and has been the operating contractor ever since. Located just west of Texarkana, Texas, LSAAP encompasses an area of approximately 15,546 acres. The primary mission of LSAAP is to load, assemble and pack ammunition and ammunition components for the Army.

NONE

1981-12-31T23:59:59.000Z

20

Audit of Lone Star Gas Invoices and Billing Procedures, Task #3  

E-Print Network [OSTI]

ownership of only the metering facilities (excluding any automatic meter reading system(s)) and Transporter will be solely responsible for all activities in connection with said metering facilities, including, but not limited to, operation, testing...

Turner, W. D.; Liu, M.

1997-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "waha lone star" 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

Development of a Synergistic, Comprehensive Statewide Lone Star Healthy Streams Program  

E-Print Network [OSTI]

resource manuals and five presentations on bacteria issues and associated BMPs for four major classes of livestock as well as feral hogs....

Wagner, K.; Redmon, L.; Peterson, J.

2013-01-01T23:59:59.000Z

22

Physiological Ageing as it is Related to Gene Function in the Lone Star Tick, Amblyomma americanum  

E-Print Network [OSTI]

............................ 15 Figure 4 Electrophoresis gel results for the expression of the 16S gene in Amblyomma americanum subdivided by the mortality percentile to the right of the result, the sample number over the top of the result, and the group... as assessed by Image J software displaying the expression of Amblyomma americaum gene 16S for the female control (FC), male control (MC), female experimental (FE), and male experimental (ME) groups from Day 0 to Day 77...

Catena, Amanda M.

2010-07-14T23:59:59.000Z

23

Doing science: teachers' authentic experiences at the Lone Star Dinosaur Field Institute  

E-Print Network [OSTI]

Winkler and Dr. Louis Jacobs also deserve special thanks for being great science teachers. Though I was engaged primarily as an educational researcher, I found myself to be a science student as well. Through the experience that the scientists help... of excavating fossils, teachers, museum educators, and scientists sat around the campfire ruminating over their experiences. The team's videographer tumed his camera on paleontologist Louis Jacobs. With the campfire in the background, Louis Jacobs took...

Stiles, Thomas William

2001-01-01T23:59:59.000Z

24

Lone Star I (4Q07) Wind Farm | Open Energy Information  

Open Energy Info (EERE)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home5b9fcbce19 No revision hasInformation Earth's Heat JumpInc Place:KeystoneSolarListLiveFuels Inc JumpLoess HillsI (4Q07)

25

Lone Star II (1Q08) Wind Farm | Open Energy Information  

Open Energy Info (EERE)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home5b9fcbce19 No revision hasInformation Earth's Heat JumpInc Place:KeystoneSolarListLiveFuels Inc JumpLoess HillsIII (1Q08)

26

Lone Star II (2Q08) Wind Farm | Open Energy Information  

Open Energy Info (EERE)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home5b9fcbce19 No revision hasInformation Earth's Heat JumpInc Place:KeystoneSolarListLiveFuels Inc JumpLoess HillsIII

27

Lone Star II (4Q07) Wind Farm | Open Energy Information  

Open Energy Info (EERE)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home5b9fcbce19 No revision hasInformation Earth's Heat JumpInc Place:KeystoneSolarListLiveFuels Inc JumpLoess HillsIII Jump to:

28

Ligand Lone-Pair Influence on Hydrocarbon C-H Activation: A Computational Perspective  

SciTech Connect (OSTI)

Mid to late transition metal complexes that break hydrocarbon C?H bonds by transferring the hydrogen to a heteroatom ligand while forming a metal?alkyl bond offer a promising strategy for C?H activation. Here we report a density functional (B3LYP, M06, and X3LYP) analysis of cis-(acac){sub 2}MX and TpM(L)X (M = Ir, Ru, Os, and Rh; acac = acetylacetonate, Tp = tris(pyrazolyl)borate; X = CH{sub 3}, OH, OMe, NH{sub 2}, and NMe{sub 2}) systems for methane C?H bond activation reaction kinetics and thermodynamics. We address the importance of whether a ligand lone pair provides an intrinsic kinetic advantage through possible electronic d{sub ?}?p{sub ?} repulsions for M?OR and M?NR{sub 2} systems versus M?CH{sub 3} systems. This involves understanding the energetic impact of the X ligand group on ligand loss, C?H bond coordination, and C?H bond cleavage steps as well as understanding how the nucleophilicity of the ligand X group, the electrophilicity of the transition metal center, and cis-ligand stabilization effect influence each of these steps. We also explore how spectator ligands and second- versus third-row transition metal centers impact the energetics of each of these C?H activation steps.

Ess, Daniel H; Gunnoe, T. Brent; Cundari, Thomas R; Goddard, William A; Periana, Roy A

2010-01-01T23:59:59.000Z

29

Evaluation and Demonstration of BMPs for Cattle on Grazing Lands for the Lone Star Healthy Streams Program  

E-Print Network [OSTI]

dissemination ........................................................... 8 Subtask 1.7 Oversight of the LSHS Project Steering Committee .......................................................... 9 Subtask 1.8 Development of the final project report... all work performed under this project including technical and financial supervision and preparation of status reports. Subtask 1.1: Preparation of quarterly progress reports TWRI prepared and submitted Quarterly Progress Reports which can be viewed...

Wagner, K.; Redmon, L.; Gentry, T.; Clary, C.

30

Electron lone pair distortion facilitated metal-insulator transition in ?-Pb{sub 0.33}V{sub 2}O{sub 5} nanowires  

SciTech Connect (OSTI)

The electronic structure of ?-Pb{sub 0.33}V{sub 2}O{sub 5} nanowires has been studied with x-ray photoelectron spectroscopy techniques. The recent synthesis of defect-free ?-Pb{sub 0.33}V{sub 2}O{sub 5} nanowires resulted in the discovery of an abrupt voltage-induced metal insulator transition. First principle calculations predicted an additional V-O-Pb hybridized “in-gap” state unique to this vanadium bronze playing a significant role in facilitating the transition. We confirm the existence, energetic position, and orbital character of the “in-gap” state. Moreover, we reveal that this state is a hybridized Pb 6s–O 2p antibonding lone pair state resulting from the asymmetric coordination of the Pb{sup 2+} ions.

Wangoh, L.; Quackenbush, N. F. [Department of Physics, Applied Physics and Astronomy, Binghamton University, Binghamton, New York 13902 (United States); Marley, P. M.; Banerjee, S. [Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, New York 14260 (United States); Sallis, S. [Materials Science and Engineering, Binghamton University, Binghamton, New York 13902 (United States); Fischer, D. A.; Woicik, J. C. [Materials Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Piper, L. F. J., E-mail: lpiper@binghamton.edu [Department of Physics, Applied Physics and Astronomy, Binghamton University, Binghamton, New York 13902 (United States); Materials Science and Engineering, Binghamton University, Binghamton, New York 13902 (United States)

2014-05-05T23:59:59.000Z

31

Chameleon stars  

SciTech Connect (OSTI)

We consider a gravitating spherically symmetric configuration consisting of a scalar field nonminimally coupled to ordinary matter in the form of a perfect fluid. For this system we find static, regular, asymptotically flat solutions for both relativistic and nonrelativistic cases. It is shown that the presence of the nonminimal interaction leads to substantial changes both in the radial matter distribution of the star and in the star's total mass. A simple stability test indicates that, for the choice of parameters used in the paper, the solutions are unstable.

Dzhunushaliev, Vladimir [Institute for Basic Research, Eurasian National University, Astana, 010008 (Kazakhstan); Institute of Physicotechnical Problems and Material Science of the NAS of the Kyrgyz Republic, 265 a, Chui Street, Bishkek, 720071 (Kyrgyzstan); Folomeev, Vladimir [Institute of Physicotechnical Problems and Material Science of the NAS of the Kyrgyz Republic, 265 a, Chui Street, Bishkek, 720071 (Kyrgyzstan); Singleton, Douglas [Institute for Basic Research, Eurasian National University, Astana, 010008 (Kazakhstan); Physics Department, CSU Fresno, Fresno, California 93740-8031 (United States)

2011-10-15T23:59:59.000Z

32

Star Power  

SciTech Connect (OSTI)

The U.S. Department of Energy's Princeton Plasma Physics Laboratory has released ''Star Power,'' a new informational video that uses dramatic and beautiful images and thought-provoking interviews to highlight the importance of the Laboratory's research into magnetic fusion.

None

2014-10-17T23:59:59.000Z

33

Star Power  

ScienceCinema (OSTI)

The U.S. Department of Energy's Princeton Plasma Physics Laboratory has released ''Star Power,'' a new informational video that uses dramatic and beautiful images and thought-provoking interviews to highlight the importance of the Laboratory's research into magnetic fusion.

None

2014-11-18T23:59:59.000Z

34

Stereo-Active Lone-Pair Control on the Ferromagnetic Behavior in VO(SeO2OH)2:A new acentric ferromagnetic material  

SciTech Connect (OSTI)

A new acentric ferromagnetic material, VO(SeO{sub 2}OH){sub 2}, has been synthesized and characterized by single crystal X-ray diffraction, second harmonic generation (SHG), and magnetization measurements. The crystal structure of VO(SeO{sub 2}OH){sub 2} consists of linear chains of corner-shared V{sup 4+}O{sub 6} octahedra that are connected by SeO{sub 2}OH groups. The material exhibits a weak SHG efficiency, comparable to {alpha}-SiO{sub 2}, and a ferromagnetic transition (T{sub C}) at 2.5 K with a saturated magnetic moment of 1.09 {mu}B per formula unit ({mu}B/FU). The origin of the ferromagnetism is explained by the suppression of the antiferromagnetic superexchange (SE) and supersuper-exchange (SSE) interactions in the intra-chain and inter-chain magnetic interactions, respectively. In addition, using first principles density functional theory (DFT) calculations, we show that the SSE interactions depend on the O(2)-Se{sup 4+}-O(3) angle. As we demonstrate, the stereoactive lone-pair on Se{sup 4+} is the driving force for the inter-chain ferromagnetic interactions.

Kim, Sang-Hwan [University of Houston, Houston; Yeon, J [University of Houston, Houston; Safa-Sefat, Athena [ORNL; Mandrus, David [ORNL; Halasyamani, P Shiv [University of Houston, Houston

2010-01-01T23:59:59.000Z

35

Petrologic and stable isotopic evidence for reaction-enhanced fluid flow during metamorphism of Precambrian-Cambrian sedimentary rocks, Lone Mountain, Nevada  

SciTech Connect (OSTI)

Upper Precambrian to Cambrian sedimentary rocks, regionally metamorphosed during the Mesozoic to produce marbles and calc-silicate rocks, were contact metamorphosed at the end of the Cretaceous by the Lone Mountain granitic pluton. Mineral assemblages within the calc-silicates were in equilibrium with H[sub 2]O-rich fluids, while the marbles were in equilibrium with more CO[sub 2]-rich fluids. Mineralogical variation between two different calc-silicate lithologies is the result of differences in bulk rock chemical composition, which also results in differences in isotopic composition between the calc-silicate lithologies. delta O-18 and delta C-13 values show differences of greater than 6 and 4 per mil respectively across lithologic boundaries between interlayered calc-silicates and between interlayered marbles and calc-silicates. The absence of any systematic variation between delta O-18 and delta C-13 values in the calc-silicates suggests that isotopic variation due to decarbonation reactions was limited. The differences in mineralogy and isotopic composition indicate that permeability was enhanced by reaction, permitting the focused flow of fluid through the calc-silicates. Calculated mass balance variations in delta O-18 based on reaction space analysis and Rayleigh decarbonation cannot explain the observed variations of delta O-18, requiring infiltration of externally derived fluids, while the delta C-13 compositions in the calc-silicates can be explained by Rayleigh decarbonation alone.

Richards, I.J.; Labotka, T.C. (Univ. of Tennessee, Knoxville, TN (United States). Dept. of Geochemical Sciences)

1992-01-01T23:59:59.000Z

36

Energy Star  

E-Print Network [OSTI]

is a joint program of: ? U.S. Environmental Protection Agency (EPA) ? U.S. Department of Energy (DOE) ? Mission: ? ?Help us all save money and protect the environment through energy efficient products and practices.? ? History: ? 1992 ? Energy... Star Label introduced for energy-efficient products ? Expanded to include technical information & tools ? Website: www.energystar.gov ESL-KT-12-10-08 CATEE 2012: Clean Air Through Energy Efficiency Conference, Galveston, TX, October 9-11, 2012...

Reihl, K.; Tullos, A.

2012-01-01T23:59:59.000Z

37

Spectral Modeling Hot Star Winds  

E-Print Network [OSTI]

supernovaeProduce supernovae (neutron stars, black holes)(neutron stars, black holes) ·· Found near birth

Cohen, David

38

Social networks for lonely objects  

E-Print Network [OSTI]

Visions of ubiquitous computing describe a network of devices that quietly supports human goals, but this may also add complexity to an already frustrating relationship between humans and their electronic objects. As we ...

Kestner, John Anthony

2010-01-01T23:59:59.000Z

39

Idaho_LonePinePeak  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr MayAtmospheric Optical Depth7-1D: Vegetation ProposedUsingFun withconfinementEtching. | EMSLtheIndustryMitch204Peak Site #0401

40

Idaho_LonePineRidge  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr MayAtmospheric Optical Depth7-1D: Vegetation ProposedUsingFun withconfinementEtching. | EMSLtheIndustryMitch204Peak Site #0401Ridge

Note: This page contains sample records for the topic "waha lone star" 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

From Neutron Stars to Strange Stars  

E-Print Network [OSTI]

This paper discusses several most intruigung astrophysical implications connected with the possible absolute stability of strange quark matter.This is followed by a discussion of two astrophysical signals that may point at the existence of quark matter in both isolated neutron stars as well as in neutron stars in low-mass x-ray binaries (LMXBs).

Fridolin Weber

2001-12-04T23:59:59.000Z

42

Star-ND (Multi-Dimensional Star-Identification)  

E-Print Network [OSTI]

In order to perform star-identification with lower processing requirements, multi-dimensional techniques are implemented in this research as a database search as well as to create star pattern parameters. New star pattern parameters are presented...

Spratling, Benjamin

2012-07-16T23:59:59.000Z

43

Neutron Stars and Fractal Dimensionality  

E-Print Network [OSTI]

We argue that the material inside Neutron stars behaves anomalously with fractal statistics and that in principle, we could induce mini Neutron stars, with the release of energy.

Burra G. Sidharth

2008-05-06T23:59:59.000Z

44

Dark Stars: A Review  

E-Print Network [OSTI]

Dark Stars (DS) are stellar objects made (almost entirely) of ordinary atomic material but powered by the heat from Dark Matter (DM) annihilation (rather than by fusion). Weakly Interacting Massive Particles (WIMPs), among the best candidates for DM, can be their own antimatter and can accumulate inside the star, with their annihilation products thermalizing with and heating the DS. The resulting DSs are in hydrostatic and thermal equilibrium. The first phase of stellar evolution in the history of the Universe may have been dark stars. Though DM constituted only $power the star for millions to billions of years. Depending on their DM environment, early DSs can become very massive ($>10^6 M_\\odot$), very bright ($>10^9 L_\\odot$), and potentially detectable with the James Webb Space Telescope (JWST). Once the DM runs out and the dark star dies, it may collapse to a black hole; thus DSs can provide seeds for the supermassive black holes observed throughout the Universe and at early times. Other sites for dark star formation exist in the Universe today in regions of high dark matter density such as the centers of galaxies. The current review briefly discusses DSs existing today but focuses on the early generation of dark stars.

Katherine Freese; Tanja Rindler-Daller; Douglas Spolyar; Monica Valluri

2015-01-10T23:59:59.000Z

45

Planets of young stars  

E-Print Network [OSTI]

Since the first massive planet in a short period orbit was discovered, the question arised how such an object could have formed. There are basically two formation scenarios: migration due to planet-disk or planet-planet interaction. Which of the two scenarios is more realistic can be found out by observing short-period planets of stars with an age between 10E7 and 10E8 yrs. The second aim of the survey is to find out how many planets originally formed, and how many of these are destroyed in the first Gyrs: Do most young, close-in planets evaporate, or spiral into the host stars? In here we report on the first results of a radial-velocity search program for planets of young stars which we began in 2004. Using HARPS, we currently monitor 85 stars with ages between 10E7 and 10E8 yrs. We show that the detection of planets of young stars is possible. Up to now, we have identified 3 planet-candidates. Taking this result together with the results of other surveys, we conclude that the frequency of massive-short period planets of young stars is not dramatically higher than that of old stars.

E. W. Guenther; E. Esposito

2007-01-10T23:59:59.000Z

46

Hyperons in neutron stars  

E-Print Network [OSTI]

Using the Dirac-Brueckner-Hartree-Fock approach, the properties of neutron-star matter including hyperons are investigated. In the calculation, we consider both time and space components of the vector self-energies of baryons as well as the scalar ones. Furthermore, the effect of negative-energy states of baryons is partly taken into account. We obtain the maximum neutron-star mass of $2.08\\,M_{\\odot}$, which is consistent with the recently observed, massive neutron stars. We discuss a universal, repulsive three-body force for hyperons in matter.

Katayama, Tetsuya

2015-01-01T23:59:59.000Z

47

Masers and star formation  

E-Print Network [OSTI]

Recent observational and theoretical advances concerning astronomical masers in star forming regions are reviewed. Major masing species are considered individually and in combination. Key results are summarized with emphasis on present science and future prospects.

Vincent L. Fish

2007-04-02T23:59:59.000Z

48

Strangeness in Neutron Stars  

E-Print Network [OSTI]

It is generally agreed on that the tremendous densities reached in the centers of neutron stars provide a high-pressure environment in which several intriguing particles processes may compete with each other. These range from the generation of hyperons to quark deconfinement to the formation of kaon condensates and H-matter. There are theoretical suggestions of even more exotic processes inside neutron stars, such as the formation of absolutely stable strange quark matter. In the latter event, neutron stars would be largely composed of strange quark matter possibly enveloped in a thin nuclear crust. This paper gives a brief overview of these striking physical possibilities with an emphasis on the role played by strangeness in neutron star matter, which constitutes compressed baryonic matter at ultra-high baryon number density but low temperature which is no accessible to relativistic heavy ion collision experiments.

Fridolin Weber; Alexander Ho; Rodrigo P. Negreiros; Philip Rosenfield

2006-04-20T23:59:59.000Z

49

Holographic Neutron Stars  

E-Print Network [OSTI]

We construct in the context of the AdS/CFT correspondence degenerate composite operators in the conformal field theory that are holographically dual to degenerate stars in anti de Sitter space. We calculate the effect of the gravitational back-reaction using the Tolman-Oppenheimer-Volkoff equations, and determine the "Chandrasekhar limit" beyond which the star undergoes gravitational collapse towards a black hole.

Jan de Boer; Kyriakos Papadodimas; Erik Verlinde

2009-07-16T23:59:59.000Z

50

Probing thermonuclear burning on accreting neutron stars.  

E-Print Network [OSTI]

??Neutron stars are the most compact stars that can be directly observed, which makes them ideal laboratories to study physics at extreme densities. Neutron stars… (more)

Keek, L.

2008-01-01T23:59:59.000Z

51

Dark Stars: A Review  

E-Print Network [OSTI]

Dark Stars (DS) are stellar objects made (almost entirely) of ordinary atomic material but powered by the heat from Dark Matter (DM) annihilation (rather than by fusion). Weakly Interacting Massive Particles (WIMPs), among the best candidates for DM, can be their own antimatter and can accumulate inside the star, with their annihilation products thermalizing with and heating the DS. The resulting DSs are in hydrostatic and thermal equilibrium. The first phase of stellar evolution in the history of the Universe may have been dark stars. Though DM constituted only $10^6 M_\\odot$), very bright ($>10^9 L_\\odot$), and potentially detectable with the James Webb Space Telescope (JWST). Once the DM runs out and the dark star dies, it may collapse to a black hole; thus DSs can provide seeds for the supermassive black holes observed throughout the Universe and at early times. Other sites for dark star formation exist in the Universe today in regions of high dark matter density such as the centers of galaxies. The curre...

Freese, Katherine; Spolyar, Douglas; Valluri, Monica

2015-01-01T23:59:59.000Z

52

Strangeness in Neutron Stars  

E-Print Network [OSTI]

It is generally agreed on that the tremendous densities reached in the centers of neutron stars provide a high-pressure environment in which numerous novel particles processes are likely to compete with each other. These processes range from the generation of hyperons to quark deconfinement to the formation of kaon condensates and H-matter. There are theoretical suggestions of even more exotic processes inside neutron stars, such as the formation of absolutely stable strange quark matter, a configuration of matter even more stable than the most stable atomic nucleus, iron. In the latter event, neutron stars would be largely composed of pure quark matter, eventually enveloped in a thin nuclear crust. No matter which physical processes are actually realized inside neutron stars, each one leads to fingerprints, some more pronounced than others though, in the observable stellar quantities. This feature combined with the unprecedented progress in observational astronomy, which allows us to see vistas with remarkable clarity that previously were only imagined, renders neutron stars to nearly ideal probes for a wide range of physical studies, including the role of strangeness in dense matter.

Fridolin Weber

2000-08-23T23:59:59.000Z

53

Spectropolarimetry of cool stars  

E-Print Network [OSTI]

In recent years, the development of spectropolarimetric techniques deeply modified our knowledge of stellar magnetism. In the case of solar-type stars, the challenge is to measure a geometrically complex field and determine its evolution over very different time frames. In this article, I summarize some important observational results obtained in this field over the last two decades and detail what they tell us about the dynamo processes that orchestrate the activity of cool stars. I also discuss what we learn from such observations about the ability of magnetic fields to affect the formation and evolution of Sun-like stars. Finally, I evoke promising directions to be explored in the coming years, thanks to the advent of a new generation of instruments specifically designed to progress in this domain.

P. Petit

2007-03-27T23:59:59.000Z

54

On the efficiency of field star capture by star clusters  

E-Print Network [OSTI]

An exciting recent finding regarding scaling relations among globular clusters is the so-called 'blue tilt': clusters of the blue sub-population follow a trend of redder colour with increasing luminosity. In this paper we evaluate to which extent field star capture over a Hubble time may explain the 'blue tilt'. We perform collisional N-body simulations to quantify the amount of field star capture occuring over a Hubble time to star clusters with 10^3 to 10^6 stars. In the simulations we follow the orbits of field stars passing through a star cluster and calculate the energy change that the field stars experience due to gravitational interaction with cluster stars during one passage through the cluster. The capture condition is that their total energy after the passage is smaller than the gravitational potential at the cluster's tidal radius. By folding this with the fly-by rates of field stars with an assumed space density as in the solar neighbourhood and a range of velocity dispersions, we derive estimates on the mass fraction of captured field stars as a function of environment. We find that integrated over a Hubble time, the ratio between captured field stars and total number of clusters stars is very low (capture is not a probable mechanism for creating the colour-magnitude trend of metal-poor globular clusters.

Steffen Mieske; Holger Baumgardt

2007-09-10T23:59:59.000Z

55

A Star on Earth  

ScienceCinema (OSTI)

At the Energy Department's Princeton Plasma Physics Lab, scientists are trying to accomplish what was once considered the realm of science fiction: create a star on Earth. The National Spherical Torus Experiment (NSTX) is a magnetic fusion device that is used to study the physics principles of spherically shaped plasmas -- hot ionized gases in which, under the right conditions, nuclear fusion will occur. Fusion is the energy source of the sun and all of the stars. Not just limited to theoretical work, the NSTX is enabling cutting-edge research to develop fusion as a future energy source.

Prager, Stewart; Zwicker, Andrew; Hammet, Greg; Tresemer, Kelsey; Diallo, Ahmed

2014-06-06T23:59:59.000Z

56

Isolating Triggered Star Formation  

SciTech Connect (OSTI)

Galaxy pairs provide a potentially powerful means of studying triggered star formation from galaxy interactions. We use a large cosmological N-body simulation coupled with a well-tested semi-analytic substructure model to demonstrate that the majority of galaxies in close pairs reside within cluster or group-size halos and therefore represent a biased population, poorly suited for direct comparison to 'field' galaxies. Thus, the frequent observation that some types of galaxies in pairs have redder colors than 'field' galaxies is primarily a selection effect. We use our simulations to devise a means to select galaxy pairs that are isolated in their dark matter halos with respect to other massive subhalos (N= 2 halos) and to select a control sample of isolated galaxies (N= 1 halos) for comparison. We then apply these selection criteria to a volume-limited subset of the 2dF Galaxy Redshift Survey with M{sub B,j} {le} -19 and obtain the first clean measure of the typical fraction of galaxies affected by triggered star formation and the average elevation in the star formation rate. We find that 24% (30.5 %) of these L* and sub-L* galaxies in isolated 50 (30) h{sup -1} kpc pairs exhibit star formation that is boosted by a factor of {approx}> 5 above their average past value, while only 10% of isolated galaxies in the control sample show this level of enhancement. Thus, 14% (20 %) of the galaxies in these close pairs show clear triggered star formation. Our orbit models suggest that 12% (16%) of 50 (30) h{sup -1} kpc close pairs that are isolated according to our definition have had a close ({le} 30 h{sup -1} kpc) pass within the last Gyr. Thus, the data are broadly consistent with a scenario in which most or all close passes of isolated pairs result in triggered star formation. The isolation criteria we develop provide a means to constrain star formation and feedback prescriptions in hydrodynamic simulations and a very general method of understanding the importance of triggered star formation in a cosmological context.

Barton, Elizabeth J.; Arnold, Jacob A.; /UC, Irvine; Zentner, Andrew R.; /KICP, Chicago /Chicago U., EFI; Bullock, James S.; /UC, Irvine; Wechsler, Risa H.; /KIPAC, Menlo

2007-09-12T23:59:59.000Z

57

Synthetic guide star generation  

DOE Patents [OSTI]

A system for assisting in observing a celestial object and providing synthetic guide star generation. A lasing system provides radiation at a frequency at or near 938 nm and radiation at a frequency at or near 1583 nm. The lasing system includes a fiber laser operating between 880 nm and 960 nm and a fiber laser operating between 1524 nm and 1650 nm. A frequency-conversion system mixes the radiation and generates light at a frequency at or near 589 nm. A system directs the light at a frequency at or near 589 nm toward the celestial object and provides synthetic guide star generation.

Payne, Stephen A. (Castro Valley, CA) [Castro Valley, CA; Page, Ralph H. (Castro Valley, CA) [Castro Valley, CA; Ebbers, Christopher A. (Livermore, CA) [Livermore, CA; Beach, Raymond J. (Livermore, CA) [Livermore, CA

2008-06-10T23:59:59.000Z

58

A Star on Earth  

SciTech Connect (OSTI)

At the Energy Department's Princeton Plasma Physics Lab, scientists are trying to accomplish what was once considered the realm of science fiction: create a star on Earth. The National Spherical Torus Experiment (NSTX) is a magnetic fusion device that is used to study the physics principles of spherically shaped plasmas -- hot ionized gases in which, under the right conditions, nuclear fusion will occur. Fusion is the energy source of the sun and all of the stars. Not just limited to theoretical work, the NSTX is enabling cutting-edge research to develop fusion as a future energy source.

Prager, Stewart; Zwicker, Andrew; Hammet, Greg; Tresemer, Kelsey; Diallo, Ahmed

2014-03-05T23:59:59.000Z

59

The Austin Energy Star Program  

E-Print Network [OSTI]

The Austin Energy Star Program is an Austin-specific energy rating system implemented in July, 1985. Since the first builders joined the program, Energy Star has gone through significant improvements vithout changing the fundamental marketing theme...

Seiter, D. L.

1988-01-01T23:59:59.000Z

60

High-gravity central stars  

E-Print Network [OSTI]

NLTE spectral analyses of high-gravity central stars by means of state-of-the-art model atmosphere techniques provide information about the precursor AGB stars. The hydrogen-deficient post-AGB stars allow investigations on the intershell matter which is apparently exhibited at the stellar surface. We summarize recent results from imaging, spectroscopy, and spectropolarimetry.

Thomas Rauch

2006-07-11T23:59:59.000Z

Note: This page contains sample records for the topic "waha lone star" 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

Energy generation in stars  

E-Print Network [OSTI]

It is a current opinion that thermonuclear fusion is the main source of the star activity. It is shown below that this source is not unique. There is another electrostatic mechanism of the energy generation which accompanies thermonuclear fusion. Probably, this approach can solve the solar neutrino problem.

B. V. Vasiliev

2001-10-29T23:59:59.000Z

62

Neutron stars and quark stars: Two coexisting families of compact stars?  

E-Print Network [OSTI]

The mass-radius relation of compact stars is discussed with relation to the presence of quark matter in the core. The existence of a new family of compact stars with quark matter besides white dwarfs and ordinary neutron stars is outlined.

J. Schaffner-Bielich

2006-12-29T23:59:59.000Z

63

Lone Working Procedure Procedure Revision No  

E-Print Network [OSTI]

, Heads of School, Directors of Research Institutes and Heads of Service 5.2 Line Managers 5.3 Health legislation in respect of working alone, the Management of Health and Safety at Work Regulations 1999' risks that employees might face in the course of their duties. The Health & Safety Executive (HSE) has

Glasgow, University of

64

ENERGY STAR Webinar: Financing Energy Efficient Upgrades with...  

Broader source: Energy.gov (indexed) [DOE]

ENERGY STAR Webinar: Financing Energy Efficient Upgrades with ENERGY STAR ENERGY STAR Webinar: Financing Energy Efficient Upgrades with ENERGY STAR October 21, 2014 2:00PM to...

65

ENERGY STAR Webinar: Financing Energy Efficient Upgrades with ENERGY STAR  

Broader source: Energy.gov [DOE]

Hosted by ENERGY STAR, this webinar will show how public sector organizations are improving energy efficiency with innovative solutions to financial barriers.

66

New Abundansec From Very Old Stars  

E-Print Network [OSTI]

Metal-poor stars hold the fossil record of the Galactic chemical evolution and nucleosynthesis processes that took place at the earliest times in the history of our Galaxy. From detailed abundance studies of low mass, extremely metal-poor stars ([Fe/H] capture. The sample includes some of the most metal-poor stars ([Fe/H] capture elements, and also a number of stars enhanced in carbon. The so called CEMP (carbon enhanced metal-poor) stars, these stars make up ~20% of the stars with [Fe/H] < -3, and 80% of the stars with [Fe/H] < -4.5. The progenitors of CEMP stars is still ...

Hansen, T; Christlieb, N; Yong, D; Beers, T C; Andersen, J

2015-01-01T23:59:59.000Z

67

Streamlining ENERGY STAR Appliance Testing  

Broader source: Energy.gov [DOE]

To save taxpayer dollars and help lower the costs of innovative energy-efficient technologies, the Energy Department is streamlining ENERGY STAR testing for appliances.

68

Home Performance with Energy Star  

Broader source: Energy.gov [DOE]

Through the Home Performance with Energy Star program, Focus on Energy offers instant rewards for installing select recommended efficiency measures following a home energy audit. Energy consultants...

69

Excavation of the first stars  

E-Print Network [OSTI]

The external pollution of the first stars in the Galaxy is investigated. The first stars were born in clouds composed of the pristine gas without heavy elements. These stars accreted gas polluted with heavy elements while they still remained in the cloud. As a result, it is found that they exhibit a distribution with respect to the surface metallicity. We have derived the actual form of this distribution function. This metallicity distribution function strongly suggests that the recently discovered most metal-deficient star HE0107-5240 with [Fe/H]=-5.3 was born as a metal-free star and accreted gas polluted with heavy elements. Thus the heavy elements such as Fe in HE0107-5240 must have been supplied from supernovae of later generations exploding inside the cloud in which the star had been formed. The elemental abundance pattern on the surface of stars suffering from such an external pollution should not be diverse but exhibit the average pattern of numerous supernovae. Future observations for a number of metal-deficient stars with [Fe/H]<-5 will be able to prove or disprove this external pollution scenario. Other possibilities to produce a star with this metallicity are also discussed.

Toshikazu Shigeyama; Takuji Tsujimoto; Yuzuru Yoshii

2003-02-17T23:59:59.000Z

70

Creating a Star on Earth  

Broader source: Energy.gov [DOE]

At the Energy Department's Princeton Plasma Physics Lab, scientists are trying to accomplish what was once considered the realm of science fiction: creating a star on Earth.

71

RHIC | STAR Detector  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr May JunDatastreamsmmcrcalgovInstrumentsrucLas ConchasPassive Solar HomePromising Science for1 20115, 2001 MediaBrookhavenBlackAThe STAR

72

Star Canticle Issue 2  

E-Print Network [OSTI]

StA ft CANtJClt 2 * 1 1 STAR CANTICLE 2 DOTTY BARRY PRICE: P.O. BOX 921 $5.50 1st class CLAREMONT, CA 91711 4.50 book rate CON TEN TS 2 Prelude 3 Poetry ?Untitled Dotty Barry k Fiction ?"Scotty? s Decision" Joy Mancinelli 6.... .Poetry..." Rayelle Roe m Poetry ?"Shouldn't You Ask Me First?" .Susan Meek k>2 Poetry ?"Storm Haven" Ellen Kobrin ^3 Poetry ?"Fire and Ice" ? ? .Gerry Downes kk Fiction ?"Viewpoint" Kay McElvain ty Poetry ?"Threads" Susan Burr 48 Poetry ?"The Starless Sky" Liz...

Multiple Contributors

1979-01-01T23:59:59.000Z

73

Cavitation from bulk viscosity in neutron stars and quark stars  

E-Print Network [OSTI]

The bulk viscosity in quark matter is sufficiently high to reduce the effective pressure below the corresponding vapor pressure during density perturbations in neutron stars and strange stars. This leads to mechanical instability where the quark matter breaks apart into fragments comparable to cavitation scenarios discussed for ultra-relativistic heavy-ion collisions. Similar phenomena may take place in kaon-condensed stellar cores. Possible applications to compact star phenomenology include a new mechanism for damping oscillations and instabilities, triggering of phase transitions, changes in gravitational wave signatures of binary star inspiral, and astrophysical formation of strangelets. At a more fundamental level it points to the possible inadequacy of a hydrodynamical treatment of these processes in compact stars.

Jes Madsen

2009-09-30T23:59:59.000Z

74

Physics of Neutron Star Crusts  

E-Print Network [OSTI]

The physics of neutron star crusts is vast, involving many different research fields, from nuclear and condensed matter physics to general relativity. This review summarizes the progress, which has been achieved over the last few years, in modeling neutron star crusts, both at the microscopic and macroscopic levels. The confrontation of these theoretical models with observations is also briefly discussed.

N. Chamel; P. Haensel

2008-12-20T23:59:59.000Z

75

Verifying the ENERGY STAR® Certification Application  

Broader source: Energy.gov [DOE]

Do you verify commercial building applications for ENERGY STAR certification? This webinar, based on the ENERGY STAR Guide for Licensed Professionals, covers the role of the licensed professional,...

76

Efficiencies of Low-Mass Star and Star Cluster Formation  

E-Print Network [OSTI]

Using a quantitative model for bipolar outflows driven by hydromagnetic protostellar winds, we calculate the efficiency of star formation assuming that available gas is either converted into stars or ejected in outflows. We estimate the efficiency of a single star formation event in a protostellar core, finding 25%-70% for cores with various possible degrees of flattening. The core mass function and the stellar initial mass function have similar slopes, because the efficiency is not sensitive to its parameters. We then consider the disruption of gas from a dense molecular clump in which a cluster of young stars is being born. In both cases, we present analytical formulae for the efficiencies that compare favorably against observations and, for clusters, against numerical simulations. We predict efficiencies in the range 30%-50% for the regions that form clusters of low-mass stars. In our model, star formation and gas dispersal happen concurrently. We neglect the destructive effects of massive stars: our results are therefore upper limits to the efficiency in regions more massive than about 3000 Msun.

Christopher D. Matzner; Christopher F. McKee

2000-07-25T23:59:59.000Z

77

The evolution of star clusters: The resolved-star approach  

E-Print Network [OSTI]

We present the first results of a new technique to detect, locate, and characterize young dissolving star clusters. Using HST/ACS archival images of the nearby galaxy IC2574, we performed stellar PSF photometry and selected the most massive stars as our first test sample. We used a group-finding algorithm on the selected massive stars to find cluster candidates. We then plot the color-magnitude diagrams for each group, and use stellar evolutionary models to estimate their age. So far, we found 79 groups with ages of up to about 100 Myr, displaying various sizes and densities.

Anne Pellerin; Martin J. Meyer; Jason Harris; Daniela Calzetti

2008-02-29T23:59:59.000Z

78

EPA ENERGY STAR Webinar: ENERGY STAR Portfolio Manager 201  

Broader source: Energy.gov [DOE]

Continue to learn about EPA’s ENERGY STAR Portfolio Manager tool, with a deeper dive into more advanced functionalities such as: managing and tracking changes to your property uses over time; using...

79

EPA ENERGY STAR Webcast: Value of ENERGY STAR Certification  

Broader source: Energy.gov [DOE]

For thousands of organizations, ENERGY STAR is the simple choice for saving money and demonstrating environmental leadership to the public. Lower energy costs aren't the only financial benefit of...

80

ENERGY STAR Webinar: Financing Energy Efficient Upgrades with ENERGY STAR  

Broader source: Energy.gov [DOE]

ENERGY STAR is hosting a webinar on how public sector organizations are improving energy efficiency with innovative solutions to financial barriers on Oct. 21, 2014, from 2:00 p.m. - 3:15 p.m.

Note: This page contains sample records for the topic "waha lone star" 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

EPA ENERGY STAR: Tackling Growth in Home Electronics and Small Appliances  

E-Print Network [OSTI]

behavior: the case of ENERGY STAR computers Unlike ENERGY STAR ME, participation in ENERGY STAR home

Sanchez, Marla Christine

2008-01-01T23:59:59.000Z

82

A Heavy Flavor Tracker for STAR  

SciTech Connect (OSTI)

We propose to construct a Heavy Flavor Tracker (HFT) for the STAR experiment at RHIC. The HFT will bring new physics capabilities to STAR and it will significantly enhance the physics capabilities of the STAR detector at central rapidities. The HFT will ensure that STAR will be able to take heavy flavor data at all luminosities attainable throughout the proposed RHIC II era.

Xu, Z.; Chen, Y.; Kleinfelder, S.; Koohi, A.; Li, S.; Huang, H.; Tai, A.; Kushpil, V.; Sumbera, M.; Colledani, C.; Dulinski, W.; Himmi,A.; Hu, C.; Shabetai, A.; Szelezniak, M.; Valin, I.; Winter, M.; Surrow,B.; Van Nieuwenhuizen, G.; Bieser, F.; Gareus, R.; Greiner, L.; Lesser,F.; Matis, H.S.; Oldenburg, M.; Ritter, H.G.; Pierpoint, L.; Retiere, F.; Rose, A.; Schweda, K.; Sichtermann, E.; Thomas, J.H.; Wieman, H.; Yamamoto, E.; Kotov, I.

2005-03-14T23:59:59.000Z

83

X-ray Emission from Massive Stars  

E-Print Network [OSTI]

X-ray Emission from Massive Stars David Cohen Department of Physics and Astronomy Swarthmore be related to the production of X-rays on massive stars. If so, massive stars' X-rays are much different than those found our own Sun and other cooler stars like the Sun that produce X-rays via magnetic activity

Cohen, David

84

The STAR Vertex Position Detector  

E-Print Network [OSTI]

The 2x3 channel pseudo Vertex Position Detector (pVPD) in the STAR experiment at RHIC has been upgraded to a 2x19 channel detector in the same acceptance, called the Vertex Position Detector (VPD). This detector is fully integrated into the STAR trigger system and provides the primary input to the minimum-bias trigger in Au+Au collisions. The information from the detector is used both in the STAR Level-0 trigger and offline to measure the location of the primary collision vertex along the beam pipe and the event "start time" needed by other fast-timing detectors in STAR. The offline timing resolution of single detector channels in full-energy Au+Au collisions is ~100 ps, resulting in a start time resolution of a few tens of picoseconds and a resolution on the primary vertex location of ~1 cm.

W. J. Llope; J. Zhou; T. Nussbaum; G. W. Hoffmann; K. Asselta; J. D. Brandenburg; J. Butterworth; T. Camarda; W. Christie; H. J. Crawford; X. Dong; J. Engelage; G. Eppley; F. Geurts; J. Hammond; E. Judd; D. L. McDonald; C. Perkins; L. Ruan; J. Scheblein; J. J. Schambach; R. Soja; K. Xin; C. Yang

2014-03-26T23:59:59.000Z

85

ENERGY STAR Portfolio Manager 101  

Office of Energy Efficiency and Renewable Energy (EERE)

Join us as we introduce and demonstrate the core functionality of EPA’s ENERGY STAR Portfolio Manager tool. Attendees will learn how to: navigate Portfolio Manager; add a property and enter details...

86

ENERGY STAR Portfolio Manager 201  

Office of Energy Efficiency and Renewable Energy (EERE)

Continue to learn about EPA’s new ENERGY STAR Portfolio Manager tool, with a deeper dive into more advanced functionalities such as: managing and tracking changes to your property uses over time;...

87

Star Lakes and Rivers (Minnesota)  

Broader source: Energy.gov [DOE]

An association organized for the purpose of addressing issues on a specific lake or river, a lake improvement district, or a lake conservation district may apply to the Star Lake Board for...

88

Gravitational Waves from Relativistic Stars  

E-Print Network [OSTI]

Stellar pulsations in rotating relativistic stars are reviewed. Slow rotation approximation is applied to solving the Einstein equations. The rotational effects on the non-axisymmetric oscillations are explicitly shown in the polar and axial modes.

Yasufumi Kojima

2000-02-23T23:59:59.000Z

89

NYSERDA- Energy Star Home Builders  

Broader source: Energy.gov [DOE]

NYSERDA offers a program to encourage more industry involvement in the building of Energy Star rated Homes. Incentives are available for newly constructed residential dwellings of 3 stories or less...

90

Inversion of the star transform  

E-Print Network [OSTI]

We define the star transform as a generalization of the broken ray transform introduced by us in previous work. The advantages of using the star transform include the possibility to reconstruct the absorption and the scattering coefficients of the medium separately and simultaneously (from the same data) and the possibility to utilize scattered radiation which, in the case of the conventional X-ray tomography, is discarded. In this paper, we derive the star transform from physical principles, discuss its mathematical properties and analyze numerical stability of inversion. In particular, it is shown that stable inversion of the star transform can be obtained only for configurations involving odd number of rays. Several computationally-efficient inversion algorithms are derived and tested numerically.

Fan Zhao; John C. Schotland; Vadim A. Markel

2014-05-06T23:59:59.000Z

91

GRBs from the First Stars  

SciTech Connect (OSTI)

We present an estimate of the Gamma Ray Bursts which should be expected from metal-free, elusive first generation of stars known as PopulationIII (PopIII). We derive the GRB rate from these stars from the Stellar Formation Rate obtained in several Reionization scenarios available in the literature. In all of the analyzed models we find that GRBs from PopIII are subdominant with respect to the ''standard'' (PopII) ones up to z {approx} 10.

Iocco, Fabio; /Naples U. /KIPAC, Menlo Park

2007-04-16T23:59:59.000Z

92

STAR Vertex Detector Upgrade Development  

SciTech Connect (OSTI)

We report on the development and prototyping efforts undertaken with the goal of producing a micro-vertex detector for the STAR experiment at the RHIC accelerator at BNL. We present the basic detector requirements and show a sensor development path, conceptual mechanical design candidates and readout architecture. Prototyping and beam test results with current generation MimoSTAR-2 sensors and a readout system featuring FPGA based on-the-fly hit finding and data sparsification are also presented.

Greiner, Leo C.; Matis, Howard S.; Stezelberger, Thorsten; Vu,Chinh Q.; Wieman, Howard; Szelezniak, Michal; Sun, Xiangming

2008-01-28T23:59:59.000Z

93

Magnesium Isotopes in Halo Stars  

E-Print Network [OSTI]

We have determined Mg isotope ratios in halo field dwarfs and giants in the globular cluster M71 based on high S/N high spectral resolution (R = 10$^5$) Keck HIRES spectra. Unlike previous claims of an important contribution from intermediate-mass AGB stars to the Galactic halo, we find that our $^{26}$Mg/$^{24}$Mg ratios can be explained by massive stars.

Jorge Melendez; Judith G. Cohen

2007-08-29T23:59:59.000Z

94

Helium in Chemically Peculiar Stars  

E-Print Network [OSTI]

For the purpose of deriving the helium abundances in chemically peculiar stars, the importance of assuming a correct helium abundance has been investigated for determining the effective temperature and gravity of main sequence B-type stars, making full use of the present capability of reproducing their helium lines. Even if the flux distribution of main sequence B-type stars appears to depend only on the effective temperature for any helium abundance, the effective temperature, gravity and helium abundance have to be determined simultaneously by matching the Balmer line profiles. New MULTI NLTE calculations, performed adopting ATLAS9 model atmospheres and updated helium atomic parameters, reproduce most of the observed equivalent widths of neutral helium lines for main sequence B-type stars and they make us confident of the possibility to correctly derive the helium abundance in chemically peculiar stars. An application of previous methods to the helium rich star HD 37017 shows that helium could be stratified in the magnetic pole regions, as expected in the framework of the diffusion theory in the presence of mass loss.

F. Leone

1998-05-05T23:59:59.000Z

95

Upsilon Productions at STAR  

E-Print Network [OSTI]

The $\\Upsilon(1S+2S+3S)\\to e^{+}e^{-}$ cross section is measured at mid-rapidity ($y$) in $p+p$ collisions and in d$+Au$ collisions at center-of-mass energy $\\sqrt{s}$ = 200 GeV with the STAR detector at RHIC. In $p+p$, the measured cross section is found to be consistent with the world data trend as a function of $\\sqrt{s}$, in agreement with the Color Evaportaion Model (CEM), and underestimated by the Color Singlet Model (CSM) up to the Next-to-Leading-Order Quantum Chromodynamics (NLO QCD) calculations. In d+$Au$, the measured cross section is in agreement with the CEM prediction with anti-shadowing effects, and the nuclear modification factor indicates that $\\Upsilon(1S+2S+3S)$ production follows binary scaling within the current uncertainties. These measurements provide a benchmark for the future measurements of $\\Upsilon$ production in $Au+Au$ collisions.

A. M. Hamed

2010-05-22T23:59:59.000Z

96

Feedback from Protostellar Outflows in Star and Star Cluster Formation  

E-Print Network [OSTI]

Magnetic stresses collimate protostellar winds into a common distribution of force with angle. Sweeping into the ambient medium, such winds drive bipolar molecular outflows whose properties are insensitive to the distribution of ambient gas and to the details of how the wind is launched, and how its intensity varies over time. Moreover, these properties are in accord with the commonly observed features of outflows. This model is simple enough to permit a quantitative study of the feedback effects from low-mass star formation. It predicts the rate at which star-forming gas is ejected by winds, and hence the efficiency with which stars form. Applied to individual star formation, it relates the stellar initial mass function to the distribution of pre-stellar cores. Applied to cluster formation, it indicates whether the resulting stellar system will remain gravitationally bound. Using the energy injection and mass ejection implied by this model, we investigate the dynamical evolution of a molecular clump as a stellar cluster forms within it. This depends critically on the rate at which turbulence decays: it may involve equilibrium star formation (slow decay), overstable oscillations, or collapse (fast decay).

Christopher D. Matzner

2000-07-13T23:59:59.000Z

97

ENERGY STAR Test Procedures and Verification | Department of...  

Energy Savers [EERE]

ENERGY STAR ENERGY STAR Test Procedures and Verification ENERGY STAR Test Procedures and Verification The Department of Energy (DOE) is the lead agency in the development and...

98

Toy Stars in two dimensions  

E-Print Network [OSTI]

Toy Stars are gas masses where the compressibility is treated without approximations but gravity is replaced by a force which, for any pair of masses, is along their line of centres and proportional to their separation. They provide an invaluable resource for testing the suitability of numerical codes for astrophysical gas dynamics. In this paper we derive the equations for both small amplitude oscillations and non linear solutions for rotating and pulsating Toy Stars in two dimensions, and show that the solutions can be reduced to a small number of ordinary differential equations. We compare the accurate solutions of these equations with Smoothed Particle Hydrodynamics (SPH) simulations. The two dimensional Toy Star solutions are found to provide an excellent benchmark for SPH algorithms, highlighting many of the strengths and also some weaknesses of the method.

J. J. Monaghan; D. J. Price

2005-10-25T23:59:59.000Z

99

The Star Formation History of NGC 6822  

E-Print Network [OSTI]

Images of five fields in the Local Group dwarf irregular galaxy NGC 6822 obtained with the {\\it Hubble Space Telescope} in the F555W and F814W filters are presented. Photometry for the stars in these images was extracted using the Point-Spread-Function fitting program HSTPHOT/MULTIPHOT. The resulting color-magnitude diagrams reach down to $V\\approx26$, a level well below the red clump, and were used to solve quantitatively for the star formation history of NGC 6822. Assuming that stars began forming in this galaxy from low-metallicity gas and that there is little variation in the metallicity at each age, the distribution of stars along the red giant branch is best fit with star formation beginning in NGC 6822 12-15 Gyr ago. The best-fitting star formation histories for the old and intermediate age stars are similar among the five fields and show a constant or somewhat increasing star formation rate from 15 Gyr ago to the present except for a possible dip in the star formation rate from 3 to 5 Gyr ago. The main differences among the five fields are in the higher overall star formation rate per area in the bar fields as well as in the ratio of the recent star formation rate to the average past rate. These variations in the recent star formation rate imply that stars formed within the past 0.6 Gyr are not spatially very well mixed throughout the galaxy.

Ted K. Wyder

2001-07-31T23:59:59.000Z

100

Nuclear Physics of Neutron Stars  

E-Print Network [OSTI]

Understanding the equation of state (EOS) of cold nuclear matter, namely, the relation between the pressure and energy density, is a central goal of nuclear physics that cuts across a variety of disciplines. Indeed, the limits of nuclear existence, the collision of heavy ions, the structure of neutron stars, and the dynamics of core-collapse supernova, all depend critically on the equation of state of hadronic matter. In this contribution I will concentrate on the special role that nuclear physics plays in constraining the EOS of cold baryonic matter and its impact on the properties of neutron stars.

J. Piekarewicz

2009-01-28T23:59:59.000Z

Note: This page contains sample records for the topic "waha lone star" 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

The Cooling of Compact Stars  

E-Print Network [OSTI]

The cooling of a compact star depends very sensitively on the state of dense matter at supranuclear densities, which essentially controls the neutrino emission, as well as on the structure of the stellar outer layers which control the photon emission. Open issues concern the hyperon population, the presence of meson condensates, superfluidity and superconductivity, and the transition of confined hadronic matter to quark matter. This paper describes these issues and presents cooling calculations based on a broad collection of equations of state for neutron star matter and strange matter. These results are tested against the body of observed cooling data.

Dany Page; Ulrich Geppert; Fridolin Weber

2005-08-01T23:59:59.000Z

102

Neutron skins and neutron stars  

SciTech Connect (OSTI)

The neutron-skin thickness of heavy nuclei provides a fundamental link to the equation of state of neutron-rich matter, and hence to the properties of neutron stars. The Lead Radius Experiment ('PREX') at Jefferson Laboratory has recently provided the first model-independence evidence on the existence of a neutron-rich skin in {sup 208}Pb. In this contribution we examine how the increased accuracy in the determination of neutron skins expected from the commissioning of intense polarized electron beams may impact the physics of neutron stars.

Piekarewicz, J. [Department of Physics, Florida State University, Tallahassee, FL 32306-4350 (United States)

2013-11-07T23:59:59.000Z

103

Equator Appliance: ENERGY STAR Referral (EZ 3720)  

Broader source: Energy.gov [DOE]

DOE referred Equator Appliance clothes washer EZ 3720 to EPA, brand manager of the ENERGY STAR program, for appropriate action after DOE testing revealed that the model does not meet ENERGY STAR requirements.

104

Haier: ENERGY STAR Referral (ESA3087)  

Broader source: Energy.gov [DOE]

DOE referred Haier room air conditioner model ESA3087 to EPA, brand manager of the ENERGY STAR program, for appropriate action after DOE testing revealed that the model does not meet ENERGY STAR requirements.

105

Hubble Sees a Neutron Star Alone in Space Nearest Known Neutron Star  

E-Print Network [OSTI]

Hubble Sees a Neutron Star Alone in Space Nearest Known Neutron Star #12;Birth of a Neutron Star In the core, nuclei are smashed into protons & neutrons; the protons combine with electrons to make neutrons & neutrinos. The birth temperature of a neutron star is ~5Ã?1011 K, but neutrino emission cools it to `only

Barnes, Joshua Edward

106

Gas & Stars Aging low-mass stars eject their outer layers.  

E-Print Network [OSTI]

Recycling Gas & Stars #12;Aging low-mass stars eject their outer layers. M57:The Ring Nebula #12;Thor's Emerald Helmet Winds from high-mass stars blow bubbles of hot gas. #12;Supernova blast waves in stars are mixed back into the gas. NGC 6992: Filaments of theVeil Nebula #12;Bubbles blown by high

Barnes, Joshua Edward

107

ENERGY STAR Guide to Retro-Commissioning  

Broader source: Energy.gov [DOE]

ENERGY STAR Guide to Retro-Commissioning gives an overview of RCx and provides detailed project guidance.

108

NuSTAR: Nuclear Spectroscopic Telescope Array  

SciTech Connect (OSTI)

Bill Craig, an astrophysicist at Lawrence Livermore National Laboratory, describes the NASA NuSTAR mission, launched June 13, 2012.

Craig, Bill

2012-06-13T23:59:59.000Z

109

NuSTAR: Nuclear Spectroscopic Telescope Array  

ScienceCinema (OSTI)

Bill Craig, an astrophysicist at Lawrence Livermore National Laboratory, describes the NASA NuSTAR mission, launched June 13, 2012.

Craig, Bill

2014-06-24T23:59:59.000Z

110

The nuclear physics of neutron stars  

SciTech Connect (OSTI)

We explore the unique and fascinating structure of neutron stars. Although neutron stars are of interest in many areas of Physics, our aim is to provide an intellectual bridge between Nuclear Physics and Astrophysics. We argue against the naive perception of a neutron star as a uniform assembly of neutrons packed to enormous densities. Rather, by focusing on the many exotic phases that are speculated to exist in a neutron star, we show how the reality is different and far more interesting.

Piekarewicz, J. [Department of Physics, Florida State University, Tallahassee, FL 32306-4350 (United States)

2014-05-09T23:59:59.000Z

111

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

112

Is Her X-1 a strange star?  

E-Print Network [OSTI]

The possible identification of Her X-1 with a strange star (Li et al. 1995) is shown to be incorrect.

Jes Madsen

1996-01-23T23:59:59.000Z

113

The Chandrasekhar limit for quark stars  

E-Print Network [OSTI]

The Chandrasekhar limit for quark stars is evaluated from simple energy balance relations, as proposed by Landau for white dwarfs or neutron stars. It has been found that the limit for quark stars depends on, in addition to the fundamental constants, the Bag constant.

Shibaji Banerjee; Sanjay K. Ghosh; Sibaji Raha

2000-01-14T23:59:59.000Z

114

STAR Highlights on Heavy Ion Physics  

E-Print Network [OSTI]

RHIC-STAR is a mid-rapidity collider experiment for studying high energy nuclear collisions. The main physics goals of STAR experiment are 1) studying the properties of the strongly coupled Quark Gluon Plasma, 2) explore the QCD phase diagram structure. In these proceedings, we will review the recent results of heavy ion physics at STAR.

Shusu Shi

2014-09-30T23:59:59.000Z

115

The apsidal motion in close binary stars  

E-Print Network [OSTI]

It is usually accepted to consider an apsidal motion in binary stars as a direct confirmation that a substance inside stars is not uniformly distributed. It is shown in this paper that the apsidal motion in binary systems observation data is in a good agreement with an existence of uniform plasma cores inside stars if they consist of hydrogen-deuterium-helium mixture.

B. V. Vasiliev

2001-10-10T23:59:59.000Z

116

Boson Stars with Nontrivial Topology  

E-Print Network [OSTI]

We construct boson star solutions in the presence of a phantom field, allowing for a nontrivial topology of the solutions. The wormholes residing at the core of the configurations lead to a number of qualitative changes of the boson star solutions. In particular, the typical spiraling dependence of the mass and the particle number on the frequency of the boson stars is lost. Instead, the boson stars with nontrivial topology approach a singular configuration in the limit of vanishing frequency. Depending on the value of the coupling constant, the wormhole geometry changes from a single throat configuration to a double throat configuration, featuring a belly inbetween the two throats. Depending on the mass of the boson field and its self-interaction, the mass and the size of these objects cover many orders of magnitude, making them amenable to various astrophysical observations. A stability analysis reveals, that the unstable mode of the Ellis wormhole is retained in the presence of the bosonic matter. However, the negative eigenvalue can get very close to zero, by tuning the parameters of the self-interaction potential appropriately.

Vladimir Dzhunushaliev; Vladimir Folomeev; Christian Hoffmann; Burkhard Kleihaus; Jutta Kunz

2014-09-24T23:59:59.000Z

117

Star Formation and Galaxy Environment  

E-Print Network [OSTI]

The dependence of star formation rate on galaxian environment is a key issue in the understanding of galaxy formation and evolution. However, the study of this subject is complex and observationally challenging. This paper reviews some of the current results, drawing mostly from recent large redshift surveys such the LCRS, the MORPH collaboration, and the CNOC1 and CNOC2 redshift surveys.

H. K. C. Yee

2000-04-05T23:59:59.000Z

118

Torsional oscillations of strange stars  

E-Print Network [OSTI]

Strange stars are one of the hypothetical compact stellar objects that can be formed after a supernova explosion. The existence of these objects relies on the absolute stability of strange {\\it collapsed} quark matter with respect to standard nuclear matter. We discuss simple models of strange stars with a bare quark matter surface, thus standard nuclear matter is completely absent. In these models an electric dipole layer a few hundreds Fermi thick should exist close to the star surface. Studying the torsional oscillations of the electrically charged layer we estimate the emitted power, finding that it is of the order of $10^{45}$ erg/s, meaning that these objects would be among the brightest compact sources in the heavens. The associated relaxation times are very uncertain, with values ranging between microseconds and minutes, depending on the crust thickness. Although part of the radiated power should be absorbed by the electrosphere surrounding the strange star, a sizable fraction of photons should escape and be detectable.

Massimo Mannarelli

2014-09-12T23:59:59.000Z

119

BPS Skyrmions as neutron stars  

E-Print Network [OSTI]

The BPS Skyrme model has been demonstrated already to provide a physically intriguing and quantitatively reliable description of nuclear matter. Indeed, the model has both the symmetries and the energy-momentum tensor of a perfect fluid, and thus represents a field theoretic realization of the "liquid droplet" model of nuclear matter. In addition, the classical soliton solutions together with some obvious corrections (spin-isospin quantization, Coulomb energy, proton-neutron mass difference) provide an accurate modeling of nuclear binding energies for heavier nuclei. These results lead to the rather natural proposal to try to describe also neutron stars by the BPS Skyrme model coupled to gravity. We find that the resulting self-gravitating BPS Skyrmions provide excellent results as well as some new perspectives for the description of bulk properties of neutron stars when the parameter values of the model are extracted from nuclear physics. Specifically, the maximum possible mass of a neutron star before black-hole formation sets in is a few solar masses, the precise value depending on the precise values of the model parameters, and the resulting neutron star radius is of the order of 10 km.

C. Adam; C. Naya; J. Sanchez-Guillen; R. Vazquez; A. Wereszczynski

2014-07-14T23:59:59.000Z

120

Dark Stars: the First Stars in the Universe may be powered by Dark Matter Heating  

E-Print Network [OSTI]

A new line of research on Dark Stars is reviewed, which suggests that the first stars to exist in the universe were powered by dark matter heating rather than by fusion. Weakly Interacting Massive Particles, which may be there own antipartmers, collect inside the first stars and annihilate to produce a heat source that can power the stars. A new stellar phase results, a Dark Star, powered by dark matter annihilation as long as there is dark matter fuel.

Katherine Freese; Peter Bodenheimer; Paolo Gondolo; Douglas Spolyar

2008-12-28T23:59:59.000Z

Note: This page contains sample records for the topic "waha lone star" 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

Nuclear and gravitational energies in stars  

E-Print Network [OSTI]

The force that governs the evolution of stars is gravity. Indeed this force drives star formation, imposes thermal and density gradients into stars at hydrostatic equilibrium and finally plays the key role in the last phases of their evolution. Nuclear power in stars governs their lifetimes and of course the stellar nucleosynthesis. The nuclear reactions are at the heart of the changes of composition of the baryonic matter in the Universe. This change of composition, in its turn, has profound consequences on the evolution of stars and galaxies. The energy extracted from the gravitational, respectively nuclear reservoirs during the lifetimes of stars of different masses are estimated. It is shown that low and intermediate mass stars (M 8 Msol), which explode in a supernova explosion, extract more than 5 times more energy from the gravitational reservoir than from the nuclear one. We conclude by discussing a few important nuclear reactions and their link to topical astrophysical questions.

Meynet, Georges; Ekström, Sylvia

2013-01-01T23:59:59.000Z

122

Massive Stars and their Supernovae  

E-Print Network [OSTI]

Massive stars and their supernovae are prominent sources of radioactive isotopes, the observations of which thus can help to improve our astrophysical models of those. Our understanding of stellar evolution and the final explosive endpoints such as supernovae or hypernovae or gamma-ray bursts relies on the combination of magneto-hydrodynamics, energy generation due to nuclear reactions accompanying composition changes, radiation transport, and thermodynamic properties (such as the equation of state of stellar matter). Nuclear energy production includes all nuclear reactions triggered during stellar evolution and explosive end stages, also among unstable isotopes produced on the way. Radiation transport covers atomic physics (e.g. opacities) for photon transport, but also nuclear physics and neutrino nucleon/nucleus interactions in late phases and core collapse. Here we want to focus on the astrophysical aspects, i.e. a description of the evolution of massive stars and their endpoints, with a special emphasis ...

Thielemann, Friedrich-Karl; Liebendörfer, Matthias; Diehl, Roland; 10.1007/978-3-642-12698-7_4

2010-01-01T23:59:59.000Z

123

BLAST Autonomous Daytime Star Cameras  

E-Print Network [OSTI]

We have developed two redundant daytime star cameras to provide the fine pointing solution for the balloon-borne submillimeter telescope, BLAST. The cameras are capable of providing a reconstructed pointing solution with an absolute accuracy autonomous. An internal computer controls the temperature, adjusts the focus, and determines a real-time pointing solution at 1 Hz. The mechanical details and flight performance of these instruments are presented.

Marie Rex; Edward Chapin; Mark J. Devlin; Joshua Gundersen; Jeff Klein; Enzo Pascale; Donald Wiebe

2006-05-01T23:59:59.000Z

124

ENERGY STAR | Open Energy Information  

Open Energy Info (EERE)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on Office of InspectorConcentrating Solar Power Basics (The followingDirectLow Carbon TransitionENERGY STAR Jump to:

125

Neutron stars and strange stars in the chiral SU(3) quark mean field model  

E-Print Network [OSTI]

We investigate the equations of state for pure neutron matter and strange hadronic matter in $\\beta$-equilibrium, including $\\Lambda$, $\\Sigma$ and $\\Xi$ hyperons. The masses and radii of pure neutron stars and strange hadronic stars are obtained. For a pure neutron star, the maximum mass is about $1.8 M_{\\mathrm{sun}}$, while for a strange hadronic star, the maximum mass is around $1.45 M_{\\mathrm{sun}}$. The typical radii of pure neutron stars and strange hadronic stars are about 11.0-12.3 km and 10.7-11.7 km, respectively.

P. Wang; S. Lawley; D. B. Leinweber; A. W. Thomas; A. G. Williams

2005-06-06T23:59:59.000Z

126

Winds of Planet Hosting Stars  

E-Print Network [OSTI]

The field of exoplanetary science is one of the most rapidly growing areas of astrophysical research. As more planets are discovered around other stars, new techniques have been developed that have allowed astronomers to begin to characterise them. Two of the most important factors in understanding the evolution of these planets, and potentially determining whether they are habitable, are the behaviour of the winds of the host star and the way in which they interact with the planet. The purpose of this project is to reconstruct the magnetic fields of planet hosting stars from spectropolarimetric observations, and to use these magnetic field maps to inform simulations of the stellar winds in those systems using the Block Adaptive Tree Solar-wind Roe Upwind Scheme (BATS-R-US) code. The BATS-R-US code was originally written to investigate the behaviour of the Solar wind, and so has been altered to be used in the context of other stellar systems. These simulations will give information about the velocity, pressur...

Nicholson, B A; Brookshaw, L; Vidotto, A A; Carter, B D; Marsden, S C; Soutter, J; Waite, I A; Horner, J

2015-01-01T23:59:59.000Z

127

Magnetic fields in Neutron Stars  

E-Print Network [OSTI]

Isolated neutron stars show a diversity in timing and spectral properties, which has historically led to a classification in different sub-classes. The magnetic field plays a key role in many aspects of the neutron star phenomenology: it regulates the braking torque responsible for their timing properties and, for magnetars, it provides the energy budget for the outburst activity and high quiescent luminosities (usually well above the rotational energy budget). We aim at unifying this observational variety by linking the results of the state-of-the-art 2D magneto-thermal simulations with observational data. The comparison between theory and observations allows to place two strong constraints on the physical properties of the inner crust. First, strong electrical currents must circulate in the crust, rather than in the star core. Second, the innermost part of the crust must be highly resistive, which is in principle in agreement with the presence of a novel phase of matter so-called nuclear pasta phase.

Viganò, Daniele; Miralles, Juan A; Rea, Nanda

2015-01-01T23:59:59.000Z

128

Search for bright stars with infrared excess  

SciTech Connect (OSTI)

Bright stars, stars with visual magnitude smaller than 6.5, can be studied using small telescope. In general, if stars are assumed as black body radiator, then the color in infrared (IR) region is usually equal to zero. Infrared data from IRAS observations at 12 and 25?m (micron) with good flux quality are used to search for bright stars (from Bright Stars Catalogues) with infrared excess. In magnitude scale, stars with IR excess is defined as stars with IR color m{sub 12}?m{sub 25}>0; where m{sub 12}?m{sub 25}?=??2.5log(F{sub 12}/F{sub 25})+1.56, where F{sub 12} and F{sub 25} are flux density in Jansky at 12 and 25?m, respectively. Stars with similar spectral type are expected to have similar color. The existence of infrared excess in the same spectral type indicates the existence of circum-stellar dust, the origin of which is probably due to the remnant of pre main-sequence evolution during star formation or post AGB evolution or due to physical process such as the rotation of those stars.

Raharto, Moedji, E-mail: moedji@as.itb.ac.id [Astronomy Research Division, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha 10, Bandung 40132 (Indonesia)

2014-03-24T23:59:59.000Z

129

The role of low-mass star clusters in massive star formation in Orion  

E-Print Network [OSTI]

To distinguish between the different theories proposed to explain massive star formation, it is crucial to establish the distribution, the extinction, and the density of low-mass stars in massive star-forming regions. We analyzed deep X-ray observations of the Orion massive star-forming region using the Chandra Orion Ultradeep Project (COUP) catalog. We found that pre-main sequence (PMS) low-mass stars cluster toward the three massive star-forming regions: the Trapezium Cluster (TC), the Orion Hot Core (OHC), and OMC1-S. We derived low-mass stellar densities of 10^{5} stars pc^{-3} in the TC and OMC1-S, and of 10^{6} stars pc^{-3} in the OHC. The close association between the low-mass star clusters with massive star cradles supports the role of these clusters in the formation of massive stars. The X-ray observations show for the first time in the TC that low-mass stars with intermediate extinction are clustered toward the position of the most massive star, which is surrounded by a ring of non-extincted low-ma...

Rivilla, V M; Jimenez-Serra, I; Rodriguez-Franco, A

2013-01-01T23:59:59.000Z

130

Radio Triggered Star Formation in Cooling Flows  

E-Print Network [OSTI]

The giant galaxies located at the centers of cluster cooling flows are frequently sites of vigorous star formation. In some instances, star formation appears to have been triggered by the galaxy's radio source. The colors and spectral indices of the young populations are generally consistent with short duration bursts or continuous star formation for durations much less than 1 Gyr, which is less than the presumed ages of cooling flows. The star formation properties are inconsistent with fueling by a continuously accreting cooling flow, although the prevalence of star formation is consistent with repeated bursts and periodic refueling. Star formation may be fueled, in some cases, by cold material stripped from neighboring cluster galaxies.

B. R. McNamara

1999-11-08T23:59:59.000Z

131

Sequentially Triggered Star Formation in OB Associations  

E-Print Network [OSTI]

We discuss observational evidence for sequential and triggered star formation in OB associations. We first review the star formation process in the Scorpius-Centaurus OB association, the nearest OB association to the Sun, where several recent extensive studies have allowed us to reconstruct the star formation history in a rather detailed way. We then compare the observational results with those obtained for other OB associations and with recent models of rapid cloud and star formation in the turbulent interstellar medium. We conclude that the formation of whole OB subgroups (each consisting of several thousand stars) requires large-scale triggering mechanisms such as shocks from expanding wind and supernova driven superbubbles surrounding older subgroups. Other triggering mechanisms, like radiatively driven implosion of globules, also operate, but seem to be secondary processes, forming only small stellar groups rather than whole OB subgroups with thousands of stars.

Thomas Preibisch; Hans Zinnecker

2006-10-27T23:59:59.000Z

132

Boson stars: Chemical potential and quark condensates  

E-Print Network [OSTI]

We study the properties of a star made of self-gravitating bosons gas in a mean-field approximation. A generalized set of Tolman-Oppenheimer-Volkov(TOV) equations is derived to incorporate the effect of chemical-potential in the general relativistic frame work. The metric-dependence of the chemical-potential gives a new class of solutions for the boson stars. It is demonstrated that the maximum mass and radius of the star change in a significant way when the effect of finite chemical-potential is considered. We also discuss the case of a boson star made of quark-condensates. It is found that when the self-interaction between the condensates is small as compared to their mass, the typical density is too high to form a diquark-boson star. Our results indicate that the star of quark-condensate may be formed in a low-density and high-pressure regime.

Jitesh R. Bhatt; V. Sreekanth

2010-05-06T23:59:59.000Z

133

Differences in the Cooling Behavior of Strange Quark Matter Stars and Neutron Stars  

E-Print Network [OSTI]

The general statement that hypothetical strange (quark matter) stars cool more rapidly than neutron stars is investigated in greater detail. It is found that the direct Urca process could be forbidden not only in neutron stars but also in strange stars. In this case, strange stars are slowly cooling, and their surface temperatures are more or less indistinguishable from those of slowly cooling neutron stars. Furthermore the case of enhanced cooling is reinvestigated. It shows that strange stars cool significantly more rapidly than neutron stars within the first $\\sim 30$ years after birth. This feature could become particularly interesting if continued observation of SN 1987A would reveal the temperature of the possibly existing pulsar at its center.

Christoph Schaab; Bernd Hermann; Fridolin Weber; Manfred K. Weigel

1997-02-21T23:59:59.000Z

134

Parent Stars of Extrasolar Planets. XV. Host Star Rotation Revisited with {\\it Kepler} Data  

E-Print Network [OSTI]

We employed published rotation periods of {\\it Kepler} field stars to test whether stars hosting planets tend to rotate more slowly than stars without known planets. Spectroscopic vsini observations of nearby stars with planets have indicated that they tend to have smaller visni values. We employ data for {\\it Kepler} Objects of Interest (KOIs) from the first 16 quarters of its original mission; stellar parameters are based on the analysis of the first 17 quarters. We confirm that KOI stars rotate more slowly with much greater confidence than we had previously found for nearby stars with planets. Furthermore, we find that stars with planets of all types rotate more slowly, not just stars with giant planets.

Gonzalez, Guillermo

2015-01-01T23:59:59.000Z

135

EPA ENERGY STAR Webinar: How to Apply for the ENERGY STAR Certification  

Broader source: Energy.gov [DOE]

Join us to learn about applying for ENERGY STAR Certification in Portfolio Manager. Understand the value of the ENERGY STAR certification, see the step-by-step process of applying, and gain tips to...

136

The HST contribution to neutron star astronomy  

E-Print Network [OSTI]

While isolated neutron stars (INSs) are among the brightest gamma-ray sources, they are among the faintest ones in the optical, and their study is a challenging task which require the most powerful telescopes. HST has lead neutron star optical astronomy yielding nearly all the identifications achieved since the early 1990s. Here, the major HST contributions in the optical studies of INSs and their relevance for neutron stars' astronomy are reviewed.

R. P. Mignani

2007-10-29T23:59:59.000Z

137

From nuclear matter to Neutron Stars  

E-Print Network [OSTI]

Neutron stars are the most dense objects in the observable Universe and conventionally one uses nuclear theory to obtain the equation of state (EOS) of dense hadronic matter and the global properties of these stars. In this work, we review various aspects of nuclear matter within an effective Chiral model and interlink fundamental quantities both from nuclear saturation as well as vacuum properties and correlate it with the star properties.

T. K. Jha

2009-02-02T23:59:59.000Z

138

Toward faster and more accurate star sensors using recursive centroiding and star identification  

E-Print Network [OSTI]

TOWARD FASTER AND MORE ACCURATE STAR SENSORS USING RECURSIVE CENTROIDING AND STAR IDENTIFICATION A Dissertation by MALAK ANEES SAMAAN Submitted to the O?ce of Graduate Studies of Texas A&M University in partial fulfillment of the requirements... for the degree of DOCTOR OF PHILOSOPHY August 2003 Major Subject: Aerospace Engineering TOWARD FASTER AND MORE ACCURATE STAR SENSORS USING RECURSIVE CENTROIDING AND STAR IDENTIFICATION A Dissertation by MALAK ANEES SAMAAN Submitted to Texas A&M University...

Samaan, Malak Anees

2004-09-30T23:59:59.000Z

139

F8 THE TORONTO STAR Sunday, July 22, 2001 ___________________________________________________ HENEVER Star Trek  

E-Print Network [OSTI]

-matter fuelled the warp drive that propelled those star- ships. It was dangerous stuff. Just a small glitch

Hearty, Christopher

140

Stars as resonant absorbers of gravitational waves  

E-Print Network [OSTI]

Quadrupole oscillation modes in stars can resonate with incident gravitational waves (GWs), and grow non-linear at the expense of GW energy. Stars near massive black hole binaries (MBHB) can act as GW-charged batteries, cooling radiatively. Mass-loss from these stars can prompt MBHB accretion at near-Eddington rates. GW opacity is independent of amplitude, so distant resonating stars can eclipse GW sources. Absorption by the Sun of GWs from Galactic white dwarf binaries may be detectable with second-generation space-based GW detectors as a shadow within a complex diffraction pattern.

B. McKernan; K. E. S. Ford; B. Kocsis; Z. Haiman

2014-08-28T23:59:59.000Z

Note: This page contains sample records for the topic "waha lone star" 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

Residential Energy Star Appliance Rebate Program  

Broader source: Energy.gov [DOE]

Energy Trust of Oregon offers rebates for Energy Star refrigerators, freezers and clothes washers to Oregon residential electric service customers of Portland General Electric (PGE) and Pacific...

142

A Galactic O-Star Catalog  

E-Print Network [OSTI]

We have produced a catalog of 378 Galactic O stars with accurate spectral classifications which is complete for Vweb-based version with links to online services.

J. Maíz-Apellániz; N. R. Walborn; H. Á. Galué; L. H. Wei

2003-11-09T23:59:59.000Z

143

Home Performance with Energy Star Financing  

Broader source: Energy.gov [DOE]

NYSERDA offers several options for homeowners to finance energy efficiency improvements made under the Home Performance with Energy Star program. NYSERDA partners with Energy Finance Solutions (EFS...

144

Abundances of massive stars: some recent developments  

E-Print Network [OSTI]

Thanks to their usefulness in various fields of astrophysics (e.g. mixing processes in stars, chemical evolution of galaxies), the last few years have witnessed a large increase in the amount of abundance data for early-type stars. Two intriguing results emerging since the last reviews on this topic will be discussed: (a) nearby OB stars exhibit metal abundances generally lower than the solar/meteoritic estimates; (b) evolutionary models of single objects including rotation are largely unsuccessful in explaining the CNO properties of stars in the Galaxy and in the Magellanic clouds.

T. Morel

2008-11-25T23:59:59.000Z

145

Ralf Klessen: Basel: 29. 11, 2006 Star FormationStar Formation  

E-Print Network [OSTI]

(Hubble Ultra-Deep Field, from HST Web site) #12;Ralf Klessen: Basel: 29. 11, 2006 Antennae Stars in the Milky WayStars in the Milky Way On the night sky, you see stars and dark clouds Disks in Orion (data: Mark McCaughrean)protostellar disks: dark shades in front

Klessen,Ralf

146

STARS Training Needs Assessment Learner Instructions 07/2009 1 STARS Training Needs Assessment  

E-Print Network [OSTI]

STARS Training Needs Assessment Learner Instructions 07/2009 1 STARS Training Needs Assessment. · Click the STARS (Training) tab. · Click My Training Needs in the left menu. · Click the secure link to continue to My Training Needs. On the Training Needs Assessment page, click the box to the left of every

Ford, James

147

Energy Star | Open Energy Information  

Open Energy Info (EERE)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home5b9fcbce19 NoPublic Utilities Address:011-DNA Jump37. It isInformation Contracts (ESPC) Webinar Jump to:S A JumpStar Jump

148

STAR  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr May JunDatastreamsmmcrcalgovInstrumentsrucLas ConchasPassive Solar HomePromisingStoriesSANDIA REPORTSORNRecovery ActR E Q7113SafetySupport

149

STAR-TO-STAR IRON ABUNDANCE VARIATIONS IN RED GIANT BRANCH STARS IN THE GALACTIC GLOBULAR CLUSTER NGC 3201  

SciTech Connect (OSTI)

We present the metallicity as traced by the abundance of iron in the retrograde globular cluster NGC 3201, measured from high-resolution, high signal-to-noise spectra of 24 red giant branch stars. A spectroscopic analysis reveals a spread in [Fe/H] in the cluster stars at least as large as 0.4 dex. Star-to-star metallicity variations are supported both through photometry and through a detailed examination of spectra. We find no correlation between iron abundance and distance from the cluster core, as might be inferred from recent photometric studies. NGC 3201 is the lowest mass halo cluster to date to contain stars with significantly different [Fe/H] values.

Simmerer, Jennifer; Ivans, Inese I.; Filler, Dan [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Francois, Patrick [Paris-Meudon Observatory, France and Universite de Picardie Jules Verne, F-80080 Amiens (France); Charbonnel, Corinne [Geneva Observatory, University of Geneva, Chemin des Maillettes 51, CH-1290 Versoix (Switzerland); Monier, Richard [Laboratoire Hippolyte Fizeau, Universite Nice Sophia Antipolis, Parc Valrose, F-06000 Nice (France); James, Gaeel, E-mail: jennifer@physics.utah.edu, E-mail: iii@physics.utah.edu, E-mail: dan.filler@utah.edu, E-mail: patrick.francois@obspm.fr, E-mail: corinne.charbonnel@unige.ch, E-mail: richard.monier@unice.fr, E-mail: gjames@eso.org [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei Munchen (Germany)

2013-02-10T23:59:59.000Z

150

ARCHEOLOGY OF AN ANCIENT STAR  

SciTech Connect (OSTI)

We report on the bright and late F-type star HR 3138, which, with respect to its chemistry in the [Mg/H]-[Fe/Mg] abundance plane, we identify as an old Population II member. Evolutionary tracks are, however, in conflict with this finding and instead imply an age of only {tau} = 5.6{sup -1.8}{sub +{sub 2.2}} Gyr (2{sigma}) for HR 3138. We discuss this controversy in light of existing high-precision radial velocity surveys that mostly exclude the case of a blue straggler primary and a white dwarf secondary. While it is realized that a stellar merger can principally solve the issue and there is indeed observational evidence for mass accretion on HR 3138 from the absence of lithium in its photosphere, we also consider the interesting circumstance that HR 3138 lies in the direction to the 350 pc distant, young open cluster NGC 2516. We point to the possibility that the progenitor cloud of this cluster may likewise account for former mass accretion and we argue in particular for a dynamical friction with this cloud as a plausible cause for the strikingly common Galactic rotational velocity of the field star and open cluster.

Fuhrmann, K.; Chini, R.; Haas, M.; Hackstein, M.; Ramolla, M. [Astronomisches Institut, Ruhr-Universitaet Bochum, Universitaetsstrasse 150, D-44801 Bochum (Germany); Bernkopf, J., E-mail: klaus@ing.iac.es [University of Applied Sciences Augsburg, An der Hochschule 1, D-86161 Augsburg (Germany)

2012-12-20T23:59:59.000Z

151

Parent Stars of Extrasolar Planets. VIII. Chemical Abundances for 18 Elements in 31 Stars  

E-Print Network [OSTI]

We present the results of detailed spectroscopic abundance analyses for 18 elements in 31 nearby stars with planets. The resulting abundances are combined with other similar studies of nearby stars with planets and compared to a sample of nearby stars without detected planets. We find some evidence for abundance differences between these two samples for Al, Si and Ti. Some of our results are in conflict with a recent study of stars with planets in the SPOCS database. We encourage continued study of the abundance patterns of stars with planets to resolve these discrepancies.

Guillermo Gonzalez; Chris Laws

2007-04-17T23:59:59.000Z

152

Nuclear and gravitational energies in stars  

SciTech Connect (OSTI)

The force that governs the evolution of stars is gravity. Indeed this force drives star formation, imposes thermal and density gradients into stars at hydrostatic equilibrium and finally plays the key role in the last phases of their evolution. Nuclear power in stars governs their lifetimes and of course the stellar nucleosynthesis. The nuclear reactions are at the heart of the changes of composition of the baryonic matter in the Universe. This change of composition, in its turn, has profound consequences on the evolution of stars and galaxies. The energy extracted from the gravitational, respectively nuclear reservoirs during the lifetimes of stars of different masses are estimated. It is shown that low and intermediate mass stars (M < 8 M{sub ?}) extract roughly 90 times more energy from their nuclear reservoir than from their gravitational one, while massive stars (M > 8 M{sub ?}), which explode in a supernova explosion, extract more than 5 times more energy from the gravitational reservoir than from the nuclear one. We conclude by discussing a few important nuclear reactions and their link to topical astrophysical questions.

Meynet, Georges; Ekström, Sylvia [Astronomical Observatory of Geneva University (Switzerland); Courvoisier, Thierry [ISDC, Astronomical Observatory of Geneva University (Switzerland)

2014-05-09T23:59:59.000Z

153

Hot Stars: Old-Fashioned or Trendy?  

E-Print Network [OSTI]

Spectroscopic analyses with the intention of the interpretation of the UV-spectra of the brightest stars as individuals - supernovae - or as components of star-forming regions - massive O stars - provide a powerful tool with great astrophysical potential for the determination of extragalactic distances and of the chemical composition of star-forming galaxies even at high redshifts. The perspectives of already initiated work with the new generation of tools for quantitative UV-spectroscopy of Hot Stars that have been developed during the last two decades are presented and the status of the continuing effort to construct corresponding models for Hot Star atmospheres is reviewed. Because the physics of the atmospheres of Hot Stars are strongly affected by velocity expansion dominating the spectra at all wavelength ranges, hydrodynamic model atmospheres for O-type stars and explosion models for Supernovae of Type Ia are necessary as basis for the synthesis and analysis of the spectra. It is shown that stellar parameters, abundances and stellar wind properties can be determined by the methods of spectral diagnostics already developed. Additionally, it will be demonstrated that models and synthetic spectra of Type Ia Supernovae of required quality are already available that make it possible to tackle the question of whether Supernovae Ia are standard candles in a cosmological sense and the SN-luminosity distances thus indicate accelerated expansion of the universe.

A. W. A. Pauldrach

2003-01-16T23:59:59.000Z

154

Long Baseline Interferometry of Be Stars  

E-Print Network [OSTI]

We give an introduction to interferometrical concepts and their applicability to Be stars. The first part of the paper concentrates on a short historic overview and basic principles of two-beam interferometric observations. In the second part, the VLTI/MIDI instrument is introduced and its first results on Be stars, obtained on alpha Ara and delta Cen, are outlined.

Olivier Chesneau; Thomas Rivinius

2005-10-24T23:59:59.000Z

155

The first stars: Where did they form?  

E-Print Network [OSTI]

Several emerging links between high-redshift observational cosmology and the Galactic fossil evidence found in the kinematics, metallicities and ages of Milky Way stars are discussed. In a flat Cold Dark Matter model with $\\Omega\\simeq 0.3$ that agrees with present large-scale structure observations, the oldest stars in the Milky Way should have formed in the first halos where gas was able to cool, at $z\\simeq 20$. These earliest, weakly bound dwarf galaxies probably turned only a small fraction of their gas to stars, which should be metal-poor. However, the merging rate in the early universe was much faster than the present one, so massive halos with more efficient star formation and metallicities up to the highest values present today in the bulge could have formed less than $10^9$ years after the oldest stars. The mean metallicity produced in the universe by a given redshift is related to the mean surface brightness of star-forming galaxies above this redshift, and also to the reionization epoch if galaxies were the dominant sources of ionizing radiation. The biased distribution of the early dwarf galaxies where the first stars formed should result in an age gradient with radius of the low-metallicity stars in the Milky Way, with the oldest ones concentrated in the bulge and the youngest in the outer halo.

Jordi Miralda-Escude

1999-12-15T23:59:59.000Z

156

X-ray Spectroscopy of Cool Stars  

E-Print Network [OSTI]

High-resolution X-ray spectroscopy has addressed not only various topics in coronal physics of stars, but has also uncovered important features relevant for our understanding of stellar evolution and the stellar environment. I summarize recent progress in coronal X-ray spectroscopy and in particular also discuss new results from studies of X-rays from pre-main sequence stars.

M. Guedel

2006-09-11T23:59:59.000Z

157

X-ray Emission from Massive Stars  

E-Print Network [OSTI]

X-ray Emission from Massive Stars David Cohen Department of Physics and Astronomy Swarthmore #12;What is the mechanism by which massive stars produce x-rays? New results from the Chandra X-ray Observatory ­ high-resolution x-ray spectroscopy: measuring Doppler broadening in emission lines Testing

Cohen, David

158

North Star Refrigerator: Order (2013-CE-5355)  

Broader source: Energy.gov [DOE]

DOE ordered North Star Refrigerator Co., Inc. to pay a $8,000 civil penalty after finding North Star Refrigerator had failed to certify that any basic models of walk-in cooler and freezer components comply with the applicable energy conservation standards.

159

The role of low-mass star clusters in massive star formation. The Orion Case  

E-Print Network [OSTI]

To distinguish between the different theories proposed to explain massive star formation, it is crucial to establish the distribution, the extinction, and the density of low-mass stars in massive star-forming regions. We analyze deep X-ray observations of the Orion massive star-forming region using the Chandra Orion Ultradeep Project (COUP) catalog. We studied the stellar distribution as a function of extinction, with cells of 0.03 pc x 0.03 pc, the typical size of protostellar cores. We derived stellar density maps and calculated cluster stellar densities. We found that low-mass stars cluster toward the three massive star-forming regions: the Trapezium Cluster (TC), the Orion Hot Core (OHC), and OMC1-S. We derived low-mass stellar densities of 10^{5} stars pc^{-3} in the TC and OMC1-S, and of 10^{6} stars pc^{-3} in the OHC. The close association between the low-mass star clusters with massive star cradles supports the role of these clusters in the formation of massive stars. The X-ray observations show for ...

Rivilla, V M; Jimenez-Serra, I; Rodriguez-Franco, A

2013-01-01T23:59:59.000Z

160

Gas, Stars and Star Formation in ALFALFA Dwarf Galaxies  

E-Print Network [OSTI]

We examine the global properties of the stellar and HI components of 229 low HI mass dwarf galaxies extracted from the ALFALFA survey, including a complete sample of 176 galaxies with HI masses ALFALFA dwarfs are faint and of low surface brightness; only 56% of those within the SDSS footprint have a counterpart in the SDSS spectroscopic survey. A large fraction of the dwarfs have high specific star formation rates (SSFRs) and estimates of their SFRs and M_* obtained by SED fitting are systematically smaller than ones derived via standard formulae assuming a constant SFR. The increased dispersion of the SSFR distribution at M_* < 10^8 M_sun is driven by a set of dwarf galaxies that have low gas fractions and SSFRs; some of t...

Huang, S; Giovanelli, R; Brinchmann, J; Stierwalt, S; Neff, S G

2012-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "waha lone star" 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

DOE Defends Decision to Revoke Energy Star Designation for Certain...  

Broader source: Energy.gov (indexed) [DOE]

Decision to Revoke Energy Star Designation for Certain LG Refrigerators DOE Defends Decision to Revoke Energy Star Designation for Certain LG Refrigerators December 23, 2009 -...

162

Clean Energy Action Star Governor Schwarzenegger to Keynote ARPA...  

Broader source: Energy.gov (indexed) [DOE]

Action Star Governor Schwarzenegger to Keynote ARPA-E Energy Innovation Summit Clean Energy Action Star Governor Schwarzenegger to Keynote ARPA-E Energy Innovation Summit February...

163

DOE Verification Testing in Support of ENERGY STAR, April 22...  

Broader source: Energy.gov (indexed) [DOE]

the Energy Star Verification Testing Program Comment submitted by the Association of Home Appliance Manufacturers (AHAM) regarding the Energy Star Verification Testing Program...

164

ENERGY STAR Portfolio Manager and Utility Benchmarking Programs...  

Office of Environmental Management (EM)

ENERGY STAR Portfolio Manager and Utility Benchmarking Programs: Effectiveness as a Conduit to Utility Energy Efficiency Programs ENERGY STAR Portfolio Manager and Utility...

165

Energy Department and AHAM Partner to Streamline ENERGY STAR...  

Energy Savers [EERE]

Energy Department and AHAM Partner to Streamline ENERGY STAR Testing for Washers, Dryers, Refrigerators Energy Department and AHAM Partner to Streamline ENERGY STAR Testing for...

166

Webinar: ENERGY STAR Hot Water Systems for High Performance Homes...  

Energy Savers [EERE]

Webinar: ENERGY STAR Hot Water Systems for High Performance Homes Webinar: ENERGY STAR Hot Water Systems for High Performance Homes This presentation is from the Building America...

167

Advanced Combustion Modeling with STAR-CD using Transient Flemelet...  

Broader source: Energy.gov (indexed) [DOE]

Combustion Modeling with STAR-CD using Transient Flemelet Models: TIF and TPV Advanced Combustion Modeling with STAR-CD using Transient Flemelet Models: TIF and TPV Presentation...

168

Gravitational waves from perturbed stars  

E-Print Network [OSTI]

Non radial oscillations of neutron stars are associated with the emission of gravitational waves. The characteristic frequencies of these oscillations can be computed using the theory of stellar perturbations, and they are shown to carry detailed information on the internal structure of the emitting source. Moreover, they appear to be encoded in various radiative processes, as for instance in the tail of the giant flares of Soft Gamma Repeaters. Thus, their determination is central to the theory of stellar perturbation. A viable approach to the problem consists in formulating this theory as a problem of resonant scattering of gravitational waves incident on the potential barrier generated by the spacetime curvature. This approach discloses some unexpected correspondences between the theory of stellar perturbations and the theory of quantum mechanics, and allows us to predict new relativistic effects.

Valeria Ferrari

2011-05-09T23:59:59.000Z

169

Adaptive Optics in Star Formation  

E-Print Network [OSTI]

Over the past ten years, the concept of adaptive optics has evolved from early experimental stages to a standard observing tool now available at almost all major optical and near-infrared telescope facilities. Adaptive optics will also be essential in exploiting the full potential of the large optical/infrared interferometers currently under construction. Both observations with high-angular resolution and at high contrast, and with a high point source sensitivity are facilitated by adaptive optics. Among the areas which benefit most from the use of adaptive optics are studies of the circumstellar environment (envelopes, disks, outflows), substellar companions and multiple systems, and dense young stellar populations. This contribution highlights some of the recent advances in star formation studies facilitated by adaptive optics, and gives a brief tutorial on optimized observing and data reduction strategies.

Wolfgang Brandner

2003-09-29T23:59:59.000Z

170

Anisotropic pressure and hyperons in neutron stars  

E-Print Network [OSTI]

We study the effects of anisotropic pressure on properties of the neutron stars with hyperons inside its core within the framework of extended relativistic mean field. It is found that the main effects of anisotropic pressure on neutron star matter is to increase the stiffness of the equation of state, which compensates for the softening of the EOS due to the hyperons. The maximum mass and redshift predictions of anisotropic neutron star with hyperonic core are quite compatible with the result of recent observational constraints if we use the parameter of anisotropic pressure model $h \\le 0.8$[1] and $\\Lambda \\le -1.15$ [2]. The radius of the corresponding neutron star at $M$=1.4 $M_\\odot$ is more than 13 km, while the effect of anisotropic pressure on the minimum mass of neutron star is insignificant. Furthermore, due to the anisotropic pressure in the neutron star, the maximum mass limit of higher than 2.1 $M_\\odot$ cannot rule out the presence of hyperons in the neutron star core.

A. Sulaksono

2014-12-23T23:59:59.000Z

171

Triggered star formation in the Magellanic Clouds  

E-Print Network [OSTI]

Abstract. We discuss how tidal interaction between the Large Magellanic Cloud (LMC), the Small Magellanic Cloud (SMC), and the Galaxy triggers galaxy-wide star formation in the Clouds for the last ? 0.2 Gyr based on our chemodynamical simulations on the Clouds. Our simulations demonstrate that the tidal interaction induces the formation of asymmetric spiral arms with high gas densities and consequently triggers star formation within the arms in the LMC. Star formation rate in the present LMC is significantly enhanced just above the eastern edge of the LMC’s stellar bar owing to the tidal interaction. The location of the enhanced star formation is very similar to the observed location of 30 Doradus, which suggests that the formation of 30 Doradus is closely associated with the last Magellanic collision about 0.2 Gyr ago. The tidal interaction can dramatically compress gas initially within the outer part of the SMC so that new stars can be formed from the gas to become intergalactic young stars in the inter-Cloud region (e.g., the Magellanic Bridge). The metallicity distribution function of the newly formed stars in the Magellanic Bridge has a peak of [Fe/H] ? ?0.8, which is significantly lower than the stellar metallicity of the SMC.

B. G. Elmegreen; J. Palous; Kenji Bekki

2006-01-01T23:59:59.000Z

172

WANDERING STARS: AN ORIGIN OF ESCAPED POPULATIONS  

SciTech Connect (OSTI)

We demonstrate that stars beyond the virial radii of galaxies may be generated by the gravitational impulse received by a satellite as it passes through the pericenter of its orbit around its parent. These stars may become energetically unbound (escaped stars), or may travel to further than a few virial radii for longer than a few Gyr, but still remain energetically bound to the system (wandering stars). Larger satellites (10%-100% the mass of the parent), and satellites on more radial orbits are responsible for the majority of this ejected population. Wandering stars could be observable on Mpc scales via classical novae, and on 100 Mpc scales via Type Ia supernova. The existence of such stars would imply a corresponding population of barely bound, old, high-velocity stars orbiting the Milky Way, generated by the same physical mechanism during the Galaxy's formation epoch. Sizes and properties of these combined populations should place some constraints on the orbits and masses of the progenitor objects from which they came, providing insight into the merging histories of galaxies in general and the Milky Way in particular.

Teyssier, Maureen; Johnston, Kathryn V. [Department of Astronomy, Columbia University, Pupin Physics Laboratory, 550 West 120th Street, New York, NY 10027 (United States); Shara, Michael M. [American Museum of Natural History, 79th Street and Central Park West, New York, NY 10024-5192 (United States)

2009-12-10T23:59:59.000Z

173

The Evolution of Compact Binary Star Systems  

E-Print Network [OSTI]

We review the formation and evolution of compact binary stars consisting of white dwarfs (WDs), neutron stars (NSs), and black holes (BHs). Mergings of compact binary stars are expected to be the most important sources for the forthcoming gravitational-wave (GW) astronomy. In the first part of the review, we discuss observational manifestations of close binary stars with NS and/or black components and their merger rate, crucial points in the formation and evolution of compact stars in binary systems, including the treatment of the natal kicks which NSs and BHs acquire during the core collapse of massive stars and the common envelope phase of binary evolution, which are most relevant to the merging rates of NS-NS, NS-BH and BH-BH binaries. The second part of the review is devoted mainly to formation and evolution of binary WDs and their observational manifestations, including their role as progenitors of cosmologically important thermonuclear SN Ia. We also consider AM CVn-stars which are thought to be the best verification binary GW sources for future low-frequency GW space interferometers.

Konstantin Postnov; Lev Yungelson

2014-03-21T23:59:59.000Z

174

Comment on "Three-dimensional hydrodynamic simulations of the combustion of a neutron star into a quark star"  

E-Print Network [OSTI]

If strange matter is absolutely stable, the ordinary nuclei decay to strangelets, while neutron stars convert into strange stars. Lifetimes of the ordinary nuclei are constrained experimentally to be above $\\sim 10^{33}$ years, while lifetimes of the metastable neutron stars depend on the neutron star masses and can exceed the age of the Universe. As a consequence, the neutron stars and the strange stars can coexist in the Universe. We point out that numerical simulations of the conversion of neutron stars to strange stars, performed by M. Herzog and F. K. Roepke in Phys. Rev. D 84, 083002 (2011) [arXiv:1109.0539], are focused on a region in the parameter space of strange matter, in which low-mass neutron stars and strange stars are coexistent, whereas massive neutron stars are unstable and short lived on an astronomical timescale.

M. I. Krivoruchenko; B. V. Martemyanov

2015-03-04T23:59:59.000Z

175

Comment on "Three-dimensional hydrodynamic simulations of the combustion of a neutron star into a quark star"  

E-Print Network [OSTI]

If strange matter is absolutely stable, the ordinary nuclei decay to strangelets, while neutron stars convert into strange stars. Lifetimes of the ordinary nuclei are constrained experimentally to be above $\\sim 10^{33}$ years, while lifetimes of the metastable neutron stars depend on the neutron star masses and can exceed the age of the Universe. As a consequence, the neutron stars and the strange stars can coexist in the Universe. We point out that numerical simulations of the conversion of neutron stars to strange stars, performed by M. Herzog and F. K. Roepke in Phys. Rev. D 84, 083002 (2011) [arXiv:1109.0539], are focused on a region in the parameter space of strange matter, in which low-mass neutron stars and strange stars are coexistent, whereas massive neutron stars are unstable and short lived on an astronomical timescale.

M. I. Krivoruchenko; B. V. Martemyanov

2014-11-17T23:59:59.000Z

176

Lithium abundances in exoplanet-hosts stars  

E-Print Network [OSTI]

Exoplanet-host stars (EHS) are known to present surface chemical abundances different from those of stars without any detected planet (NEHS). EHS are, on the average, overmetallic compared to the Sun. The observations also show that, for cool stars, lithium is more depleted in EHS than in NEHS. The overmetallicity of EHS may be studied in the framework of two different scenarii. We have computed main sequence stellar models with various masses, metallicities and accretion rates. The results show different profiles for the lithium destruction according to the scenario. We compare these results to the spectroscopic observations of lithium.

M. Castro; S. Vauclair; O. Richard; N. C. Santos

2008-03-20T23:59:59.000Z

177

Do Si stars undergo any magnetic braking?  

E-Print Network [OSTI]

The old question of rotational braking of Ap Si stars is revisited on the empirical side, taking advantage of the recent Hipparcos results. Field stars with various evolutionary states are considered, and it is shown that the loose correlation between their rotational period and their surface gravity is entirely compatible with conservation of angular momentum. No evidence is found for any loss of angular momentum on the Main Sequence, which confirms earlier results based on less reliable estimates of surface gravity. The importance of reliable, fundamental Teff determinations of Bp and Ap stars is emphasized.

P. North

1998-02-23T23:59:59.000Z

178

Convection and dynamo action in B stars  

E-Print Network [OSTI]

Main-sequence massive stars possess convective cores that likely harbor strong dynamo action. To assess the role of core convection in building magnetic fields within these stars, we employ the 3-D anelastic spherical harmonic (ASH) code to model turbulent dynamics within a 10 solar mass main-sequence (MS) B-type star rotating at 4 times the solar rate. We find that strong (900 kG) magnetic fields arise within the turbulence of the core and penetrate into the stably stratified radiative zone. These fields exhibit complex, time-dependent behavior including reversals in magnetic polarity and shifts between which hemisphere dominates the total magnetic energy.

Augustson, Kyle C; Toomre, Juri

2010-01-01T23:59:59.000Z

179

Combustion of a neutron star into a strange quark star: the neutrino signal  

E-Print Network [OSTI]

There are strong indications that the process of conversion of a neutron star into a strange quark star proceeds as a strong deflagration implying that in a few milliseconds almost the whole star is converted. Starting from the three-dimensional hydrodynamic simulations of the combustion process which provide the temperature profiles inside the newly born strange star, we calculate for the first time the neutrino signal that is to be expected if such a conversion process takes place. The neutrino emission is characterized by a luminosity and a duration that is typical for the signal expected from protoneutron stars and represents therefore a powerful source of neutrinos which could be possibly directly detected in case of events occurring close to our galaxy. We discuss moreover possible connections between the birth of strange stars and explosive phenomena such as Supernovae and Gamma-Ray-Bursts.

Pagliara, G; Ropke, F K

2013-01-01T23:59:59.000Z

180

Double Neutron Stars: Evidence For Two Different Neutron-Star Formation Mechanisms  

E-Print Network [OSTI]

Six of the eight double neutron stars known in the Galactic disk have low orbital eccentricities (neutron stars received only very small velocity kicks at birth. This is similar to the case of the B-emission X-ray binaries, where a sizable fraction of the neutron stars received hardly any velocity kick at birth (Pfahl et al. 2002). The masses of the second-born neutron stars in five of the six low-eccentricity double neutron stars are remarkably low (between 1.18 and 1.30 Msun). It is argued that these low-mass, low-kick neutron stars were formed by the electron-capture collapse of the degenerate O-Ne-Mg cores of helium stars less massive than about 3.5 Msun, whereas the higher-mass, higher kick-velocity neutron stars were formed by the collapses of the iron cores of higher initial mass. The absence of low-velocity single young radio pulsars (Hobbs et al. 2005) is consistent with the model proposed by Podsiadlowski et al. (2004), in which the electron-capture collapse of degenerate O-Ne-Mg cores can only occur in binary systems, and not in single stars.

E. P. J. van den Heuvel

2007-04-10T23:59:59.000Z

Note: This page contains sample records for the topic "waha lone star" 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

Blue Straggler Stars in Galactic Open Clusters and the effect of field star contamination  

E-Print Network [OSTI]

We investigate the distribution of Blue Straggler stars in the field of three open star clusters. The main purpose is to highlight the crucial role played by general Galactic disk fore-/back-ground field stars, which are often located in the same region of the Color Magnitude Diagram as Blue Straggler stars. We analyze photometry taken from the literature of 3 open clusters of intermediate/old age rich in Blue Straggler stars, and which are projected in the direction of the Perseus arm, and study their spatial distribution and the Color Magnitude Diagram. As expected, we find that a large portion of the Blue Straggler population in these clusters are simply young field stars belonging to the spiral arm. This result has important consequences on the theories of the formation and statistics of Blue Straggler stars in different population environments: open clusters, globular clusters or dwarf galaxies. As previously emphasized by many authors, a detailed membership analysis is mandatory before comparing the Blue Straggler population in star clusters against theoretical models. Moreover, these sequences of young field stars (blue plumes) are potentially powerful tracers of Galactic structure which require further consideration.

G. Carraro; R. A. Vazquez; A. Moitinho

2008-02-25T23:59:59.000Z

182

Simulations Reveal Unusual Death for Ancient Stars  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

these objects-among the Universe's first-generation of stars-would have exploded as supernovae and burned completely, leaving no remnant black hole behind. Astrophysicists at the...

183

Jennifer Granholm (Energy All Stars Presentation)  

Broader source: Energy.gov [DOE]

Former Michigan Governor Jennifer Granholm delivered this presentation advocating for an energy Race to the Top competition between the states at the Energy All Stars event on January 19, 2013, at...

184

Samsung: ENERGY STAR Referral (RF26VAB)  

Broader source: Energy.gov [DOE]

DOE referred the matter of Samsung refrigerator-freezer model RF26VAB to the EPA for appropriate action after DOE testing showed that the model does not meet the ENERGY STAR specification.

185

Dara Enterprises 1974 Star Trek Trivia Quiz  

E-Print Network [OSTI]

DARA ENTERPRISES 1974 STAR TREK TRIVIA QUIZ FILL OUT THE ENCLOSED ANSWER SHEET TO THE BEST OF YOUR KNOWLEDGE, AND RETURN IT TO THE DARA ENTERPRISES TABLE BEFORE CLOSING ON SUNDAY, FEBRUARY 17. WINNERS WILL BE ANNOUNCED AND PRIZES AWARDED...

186

Neutron stars in Einstein-aether theory  

E-Print Network [OSTI]

As current and future experiments probe strong gravitational regimes around neutron stars and black holes, it is desirable to have theoretically sound alternatives to general relativity against which to test observations. Here we study the consequences of one such generalization, Einstein-aether theory, for the properties of non-rotating neutron stars. This theory has a parameter range that satisfies all current weak-field tests. We find that within this range it leads to lower maximum neutron star masses, as well as larger surface redshifts at a particular mass, for a given nuclear equation of state. For non-rotating black holes and neutron stars, the innermost stable circular orbit is only slightly modified in this theory.

Christopher Eling; Ted Jacobson; M. Coleman Miller

2009-12-06T23:59:59.000Z

187

Condensation temperature trends among stars with planets  

E-Print Network [OSTI]

Results from detailed spectroscopic analyses of stars hosting massive planets are employed to search for trends between abundances and condensation temperatures. The elements C, S, Na, Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Ni and Zn are included in the analysis of 64 stars with planets and 33 comparison stars. No significant trends are evident in the data. This null result suggests that accretion of rocky material onto the photospheres of stars with planets is not the primary explanation for their high metallicities. However, the differences between the solar photospheric and meteoritic abundances do display a weak but significant trend with condensation temperature. This suggests that the metallicity of the sun's envelope has been enriched relative to its interior by about 0.07 dex.

Guillermo Gonzalez

2005-12-08T23:59:59.000Z

188

Binary star systems and extrasolar planets  

E-Print Network [OSTI]

For ten years, planets around stars similar to the Sun have been discovered, confirmed, and their properties studied. Planets have been found in a variety of environments previously thought impossible. The results have ...

Muterspaugh, Matthew Ward

2005-01-01T23:59:59.000Z

189

Bill Nye (Energy All Stars Presentation)  

Broader source: Energy.gov [DOE]

Bill Nye the Science Guy delivered this presentation on space and the lessons about climate change that can be gleaned from the other planets in our solar system at the Energy All Stars event on...

190

EPA ENERGY STAR Webcast: Portfolio Manager 101  

Office of Energy Efficiency and Renewable Energy (EERE)

Join us as we introduce and demonstrate the core functionality of EPA’s new ENERGY STAR Portfolio Manager tool. Attendees will learn how to: navigate the new Portfolio Manager; add a property and...

191

ENERGY STAR Webinar: Portfolio Manager 101  

Office of Energy Efficiency and Renewable Energy (EERE)

Join us as we introduce and demonstrate the core functionality of EPA’s new ENERGY STAR Portfolio Manager tool. Attendees will learn how to: navigate the new Portfolio Manager; add a property and...

192

Electron stars for holographic metallic criticality  

SciTech Connect (OSTI)

We refer to the ground state of a gravitating, charged ideal fluid of fermions held at a finite chemical potential as an ''electron star.'' In a holographic setting, electron stars are candidate gravity duals for strongly interacting finite fermion density systems. We show how electron stars develop an emergent Lifshitz scaling at low energies. This IR scaling region is a consequence of the two-way interaction between emergent quantum critical bosonic modes and the finite density of fermions. By integrating from the IR region to an asymptotically AdS{sub 4} spacetime, we compute basic properties of the electron stars, including their electrical conductivity. We emphasize the challenge of connecting UV and IR physics in strongly interacting finite density systems.

Hartnoll, Sean A.; Tavanfar, Alireza [Center for the Fundamental Laws of Nature, Harvard University, Cambridge, Massachusetts 02138 (United States)

2011-02-15T23:59:59.000Z

193

Entropy & viscosity bound of strange stars  

E-Print Network [OSTI]

At finite temperature (T) there is a link with general relativity and hydrodynamics that leads to a lower bound for the ratio of shear viscosity and entropy density (\\eta/s). We find that the bound is saturated in the simple model for quark matter that we use for strange stars at T = 80 MeV, at the surface of a strange star. At this T we have the possibility of cosmic separation of phases. We find that, although strongly correlated, the quark matter at the surface of strange stars constitute the most perfect interacting fluid permitted by nature. At the centre of the star, however, the density is higher and conditions are more like the results found for perturbative QCD.

Sibasish Laha; Taparati Gangopadhyay; Manjari Bagchi; Mira Dey; Jishnu Dey; Monika Sinha; Subharthi Ray

2007-02-08T23:59:59.000Z

194

Identifying seasonal stars in Kaurna astronomical traditions  

E-Print Network [OSTI]

Early ethnographers and missionaries recorded Aboriginal languages and oral traditions across Australia. Their general lack of astronomical training resulted in misidentifications, transcription errors, and omissions in these records. Additionally, many of these early records are fragmented. In western Victoria and southeast South Australia, many astronomical traditions were recorded, but curiously, some of the brightest stars in the sky were omitted. Scholars claimed these stars did not feature in Aboriginal traditions. This under-representation continues to be repeated in the literature, but current research shows that some of these stars may in fact feature in Aboriginal traditions and could be seasonal calendar markers. This paper uses established techniques in cultural astronomy to identify seasonal stars in the traditions of the Kaurna Aboriginal people of the Adelaide Plains, South Australia.

Hamacher, Duane W

2015-01-01T23:59:59.000Z

195

Folk Song 2, Sun, Moon, and Star  

E-Print Network [OSTI]

?????????????????????????????????? ???????????? Tape No. / Track / Item No. Sitaigou Tibetan Folk Song 2.WAV Length of track 00:02:40 Related tracks (include description/relationship if appropriate) Title of track Sun?Moon, and Star ???????? ???????????? Translation of title...

Sgrol dkar skyid

196

Relativistic harmonic oscillator model for quark stars  

E-Print Network [OSTI]

The relativistic harmonic oscillator (RHO) model of hadrons is used to study quark stars. The mass-radius relationship is obtained and compared with bag model of quark star, using Tolman-Oppenheimer-Volkoff equation. In this model, the outward degenerate pressure due to discrete Landau levels and Landau degeneracy balances the inward gravitational pressure. Where as in bag model the degenerate pressure is due to the standard continuum levels which balances the combined inward pressure due to gravitation and bag pressure. So in RHO model, the confinement effect is included in the degenerate pressure. We found a qualitative similarity, but quantitative differences in mass-radius relationship of quark stars in these two models. Masses and radii are relatively larger and the central energy densities, required for stable quark stars, are lower in RHO model than that of bag model.

Vishnu M. Bannur

2008-10-06T23:59:59.000Z

197

Electron stars for holographic metallic criticality  

E-Print Network [OSTI]

We refer to the ground state of a gravitating, charged ideal fluid of fermions held at a finite chemical potential as an `electron star'. In a holographic setting, electron stars are candidate gravity duals for strongly interacting finite fermion density systems. We show how electron stars develop an emergent Lifshitz scaling at low energies. This IR scaling region is a consequence of the two way interaction between emergent quantum critical bosonic modes and the finite density of fermions. By integrating from the IR region to an asymptotically AdS_4 spacetime, we compute basic properties of the electron stars, including their electrical conductivity. We emphasize the challenge of connecting UV and IR physics in strongly interacting finite density systems.

Sean A. Hartnoll; Alireza Tavanfar

2011-01-06T23:59:59.000Z

198

Whirlpool: ENERGY STAR Referral (ASD2524VE)  

Broader source: Energy.gov [DOE]

DOE referred the matter of Whirlpool's Amana-brand dishwasher model ASD2524VE to the EPA for appropriate action after DOE testing showed that the model does not meet the ENERGY STAR specification.

199

Cylindrically Symmetric Models of Anisotropic Compact Stars  

E-Print Network [OSTI]

In this paper we have discussed the possibility of forming anisotropic compact stars from cosmological constant as one of the competent candidates of dark energy with cylindrical symmetry. For this purpose, we have applied the analytical solution of Krori and Barua metric to a particular cylindrically symmetric spacetime. The unknown constants in Krori and Barua metric have been determined by using masses and radii of class of compact stars like 4$U$1820-30, Her X-1, SAX J 1808-3658. The properties of these stars have been analyzed in detail. In this setting the cosmological constant has been taken as a variable which depends on the radial coordinates. We have checked all the regularity conditions, stability and surface redshift of the compact stars 4$U$1820-30, Her X-1, SAX J 1808-3658.

G. Abbas; Sumara Nazeer; M. A. Meraj

2014-12-16T23:59:59.000Z

200

Pulsational models of BL Her stars  

E-Print Network [OSTI]

We present an updated and homogeneous pulsational scenario for a wide range of stellar parameters typical of BL Her stars i.e., Population II Cepheids with periods shorter than 8 days.

M. Di Criscienzo; M. Marconi; F. Caputo; S. Cassisi

2007-12-05T23:59:59.000Z

Note: This page contains sample records for the topic "waha lone star" 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

On surface tension for compact stars  

E-Print Network [OSTI]

In an earlier treatment it was demonstrated that general relativity gives higher values of surface tension in strange stars with quark matter than neutron stars.We generate the modified Tolman-Oppenheimer-Volkoff equation to incorporate anisotropic matter and use this to show that pressure anisotropy provides for a wide range of behaviour in the surface tension than is the case with isotropic pressures. In particular it is possible that anisotropy drastically decreases the value of the surface tension.

R. Sharma; S. D. Maharaj

2007-08-24T23:59:59.000Z

202

Noncommutative Gauge Theory with Covariant Star Product  

SciTech Connect (OSTI)

We present a noncommutative gauge theory with covariant star product on a space-time with torsion. In order to obtain the covariant star product one imposes some restrictions on the connection of the space-time. Then, a noncommutative gauge theory is developed applying this product to the case of differential forms. Some comments on the advantages of using a space-time with torsion to describe the gravitational field are also given.

Zet, G. [Physics Department, 'Gh. Asachi' Technical University, 700050 Iasi (Romania)

2010-08-04T23:59:59.000Z

203

Energy Star for Hospitals 2011 Update: Progression or Regression?  

E-Print Network [OSTI]

Energy Star for Hospitals 2011 Update: Progression or Regression? Brandon E. Travis1 1 Project Manager, SSRCx, 2995 Sidco Drive, Nashville, TN 37204, U.S.A. Email: btravis@ssr-inc.com Abstract: The Energy Star performance rating system...ENERGY STAR for Hospitals 2011 Update: Progression or Regression? Brandon E. Travis October 24, 2012 History of Energy Star Energy Star for Hospitals Critique & Conclusions Outline ? Benchmarks are important ? Energy efficiency void...

Travis, B.

2012-01-01T23:59:59.000Z

204

An Overview of STAR Experimental Results  

E-Print Network [OSTI]

With large acceptance and excellent particle identification, STAR is one of the best mid-rapidity collider experiments for studying high-energy nuclear collisions. The STAR experiment provides full information on initial conditions, properties of the hot and dense medium as well as the properties at freeze-out. In Au+Au collisions at $\\sqrt{s_{NN}} = 200$ GeV, STAR's focus is on the nature of the sQGP produced at RHIC. In order to explore the properties of the QCD phase diagram, since 2010, the experiment has collected sizable data sets of Au+Au collisions at the lower collision energy region where the net-baryon density is large. At the 2014 Quark Matter Conference, the STAR experiment made 16 presentations that cover physics topics including {\\it collective dynamics}, {\\it electromagnetic probes}, {\\it heavy flavor}, {\\it initial state physics}, {\\it jets}, {\\it QCD phase diagram}, {\\it thermodynamics and hadron chemistry}, and {\\it future experimental facilities, upgrades, and instrumentation} [1-16]. In this overview we will highlight a few results from the STAR experiment, especially those from the recent measurements of the RHIC beam energy scan program. At the end, instead of a summary, we will discuss STAR's near future physics programs at RHIC.

N. Xu

2014-08-15T23:59:59.000Z

205

Magnetic braking of T Tauri stars  

E-Print Network [OSTI]

We construct models for the rotation rates of T Tauri stars whose spin is regulated by magnetic linkage between the star and a surrounding accretion disc. Our models utilise a time-dependent disc code to follow the accretion process and include the effects of pre-main-sequence stellar evolution. We find that the initial disc mass controls the evolution of the star-disc system. For sufficiently massive discs, a stellar field of $\\sim$ 1 kG is able to regulate the spin rate to the observed values during the classical T Tauri phase. The field then acts to expel the disc and the star spins up at constant angular momentum as a weak-line system. Lower mass discs are ejected at an early epoch and fail to brake the star significantly. We extend the model to close binary systems, and find that the removal of angular momentum from the disc by the secondary significantly prolongs the inner disc lifetime. Such systems should therefore be relatively slow rotators. We also discuss the implications of our model for the spectral energy distributions and variability of T Tauri stars.

P. J. Armitage; C. J. Clarke

1995-12-05T23:59:59.000Z

206

Xenon in Mercury-Manganese Stars  

E-Print Network [OSTI]

Previous studies of elemental abundances in Mercury-Manganese (HgMn) stars have occasionally reported the presence of lines of the ionized rare noble gas Xe II, especially in a few of the hottest stars with Teff ~ 13000--15000 K. A new study of this element has been undertaken using observations from Lick Observatory's Hamilton Echelle Spectrograph. In this work, the spectrum synthesis program UCLSYN has been used to undertake abundance analysis assuming LTE. We find that in the Smith & Dworetsky sample of HgMn stars, Xe is vastly over-abundant in 21 of 22 HgMn stars studied, by factors of 3.1--4.8 dex. There does not appear to be a significant correlation of Xe abundance with Teff. A comparison sample of normal late B stars shows no sign of Xe II lines that could be detected, consistent with the expected weakness of lines at normal abundance. The main reason for the previous lack of widespread detection in HgMn stars is probably due to the strongest lines being at longer wavelengths than the photographic blue. The lines used in this work were 4603.03A, 4844.33A and 5292.22A.

M. M. Dworetsky; J. L. Persaud; K. Patel

2008-01-16T23:59:59.000Z

207

Experimental approach to neutron stars  

SciTech Connect (OSTI)

The equation of state (EOS) of nuclear matter is of fundamental importance in many areas of nuclear physics and astrophysics In the laboratory, there are different means to study the nuclearmatter equation of state and its density dependence in particular: nuclear masses, neutron skins, pygmy resonance, and nuclear structure at the drip line give access to nuclear matter properties at densities lower than and at saturation density ?0. Heavy ion reactions at energies above 0.1 AGeV are the only means to study nuclear matter at densities larger than normal nuclear matter density ?0. In the beamenergy range of 0.1 to 2A GeV nuclear matter is compressed upto three times ?0. Access to nuclear matter properties is achieved by simulating nuclear collisions by means of microscopic transport codes, or statistical or hydrodynamicalmodels. Characteristics of heavy-ion collisions are discussed, and experimental observables which allow to constrain nuclear matter properties by comparing experimental results with those of transport codes are presented. Special emphasis will be given to the density dependence of the symmetry energy which is the most relevant connection between neutron stars and heavy ion collisions.

Leifels, Yvonne [GSI Helmholtzzentrum für Schwerionenforschung, Planckstr. 1, 64291 Darmstadt (Germany)

2014-05-09T23:59:59.000Z

208

Lone Tree, Colorado: Energy Resources | Open Energy Information  

Open Energy Info (EERE)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data CenterFranconia, Virginia: Energy Resources Jump to:46 - 429Lacey,(Monaster AndLittletown, Arizona:Lockland, Ohio:London

209

Astronomy 9603B -Star Formation Star Formation: Astronomy 9603B (Winter 2012)  

E-Print Network [OSTI]

Astronomy 9603B - Star Formation Star Formation: Astronomy 9603B (Winter 2012) Lecturer: Prof below. Contact information: Martin Houde Associate Professor Department of Physics and Astronomy Room 207, Physics and Astronomy Building E-mail: mhoude2@uwo.ca Phone: (519) 661-2111 x: 86711 (office) Fax

Lennard, William N.

210

Magnetism in Herbig Ae/Be stars and the link to the Ap/Bp stars  

E-Print Network [OSTI]

Among the A/B stars, about 5% host large-scale organised magnetic fields. These magnetic stars show also abundance anomalies in their spectra, and are therefore called the magnetic Ap/Bp stars. Most of these stars are also slow rotators compared to the normal A and B stars. Today, one of the greatest challenges concerning the Ap/Bp stars is to understand the origin of their slow rotation and their magnetic fields. The favoured hypothesis for the latter is that the fields are fosils, which implies that the magnetic fields subsist throughout the different evolutionary phases, and in particular during the pre-main sequence phase. The existence of magnetic fields at the pre-main sequence phase is also required to explain the slow rotation of Ap/Bp stars. During the last 3 years we performed a spectropolarimetric survey of the Herbig Ae/Be stars in the field and in young clusters, in order to investigate their magnetism and rotation. These investigations have resulted in the detection and/or confirmation of magnet...

Alecian, E; Wade, G A; Bagnulo, S; Böhm, T; Bouret, J -C; Donati, J -F; Folsom, C; Grunhut, J; Landstreet, J D; Marsden, S C; Petit, P; Ramírez, J; Silvester, J

2008-01-01T23:59:59.000Z

211

Star Cluster Ecology: VII The evolution of young dense star clusters containing primordial binaries  

E-Print Network [OSTI]

We study the first 100Myr of the evolution of isolated star clusters initially containing 144179 stars, including 13107 (10%) primordial hard binaries. Our calculations include the effects of both stellar and binary evolution. Gravitational interactions among the stars are computed by direct N-body integration using high precision GRAPE-6 hardware. The evolution of the core radii and central concentrations of our simulated clusters are compared with the observed sample of young (about 100Myr) star clusters in the large Magellanic cloud. Even though our simulations start with a rich population of primordial binaries, core collapse during the early phase of the cluster evolution is not prevented. Throughout the simulations, the fraction of binaries remains roughly constant (about 10%). Due to the effects of mass segregation the mass function of intermediate-mass main-sequence stars becomes as flat as $\\alpha=-1.8$ in the central part of the cluster (where the initial Salpeter mass function had $\\alpha=-2.35$). About 6--12% of the neutron stars were retained in our simulations; the fraction of retained black holes is 40--70%. In each simulation about three neutron stars become members of close binaries with a main-sequence companion. Such a binary will eventually become an x-ray binary, when the main-sequence star starts to fill its Roche lobe. Black holes are found more frequently in binaries; in each simulated cluster we find about 11 potential x-ray binaries containing a black hole. Abstract abbreviated....

Simon Portegies Zwart; Steve McMillan; Jun Makino

2006-09-27T23:59:59.000Z

212

Novel Geometrical Models of Relativistic Stars. II. Incompressible Stars and Heavy Black Dwarfs  

E-Print Network [OSTI]

In a series of articles we describe a novel class of geometrical models of relativistic stars. Our approach to the static spherically symmetric solutions of Einstein equations is based on a careful physical analysis of radial gauge conditions. It turns out that there exist heavy black dwarfs: relativistic stars with arbitrary large mass, which are to have arbitrary small radius and arbitrary small luminosity. In the present article we mathematically prove this new phenomena, using a detailed consideration of incompressible GR stars. We study the whole two parameter family of solutions of extended TOV equations for incompressible stars. This example is used to illustrate most of the basic features of the new geometrical models of relativistic stars. Comparison with newest observational data is discussed

P. P. Fiziev

2004-09-20T23:59:59.000Z

213

Quark Matter, Massive Stars and Strange Planets  

E-Print Network [OSTI]

This paper gives an overview of the properties of all possible equilibrium sequences of compact strange-matter stars with nuclear crusts, which range from strange stars to strange dwarfs. In contrast to their non-strange counterparts, --neutron stars and white dwarfs--, their properties are determined by two (rather than one) parameters, the central star density and the density at the base of the nuclear crust. This leads to stellar strange-matter configurations whose properties are much more complex than those of the conventional sequence. As an example, two generically different categories of stable strange dwarfs are found, which could be the observed white dwarfs. Furthermore we find very low-mass strange stellar objects, with masses as small as those of Jupiter or even lighter planets. Such objects, if abundant enough in our Galaxy, should be seen by the presently performed gravitational microlensing searches. Further aspects studied in this paper concern the limiting rotational periods and the cooling behavior of neutron stars and their strange counterparts.

F. Weber; Ch. Schaab; M. K. Weigel; N. K. Glendenning

1996-04-09T23:59:59.000Z

214

Properties of Post-AGB stars  

E-Print Network [OSTI]

A review is presented of the most relevant results obtained in the last few years on this rare class of astronomical sources. Multi-wavelength analysis of an increasing number of post-AGB stars reveal that they constitute a more inhomogeneous population of stars than previously thought. The new data available allow us to study these sources with unprecedent spatial resolution and to extend our spectroscopic knowledge in a systematic way to the infrared for the first time, where crucial information is contained on the chemical composition of the gas and dust in their circumstellar shells. The overall infrared properties derived from ISO and Spitzer data can be used to trace the mass loss history and the chemical evolution of the ejected material. The new results impose severe observational constraints to the current nucleosynthesis models and suggest that the evolution is mainly determined not only by the initial mass but also by the metallicity of the progenitor star. Post-AGB samples are likely to grow in the near future with the advent of new data from space facilities like Spitzer or Akari. Studies of post-AGB stars in the galactic halo, the Magellanic Clouds and other galaxies of the Local Group will certainly improve our knowledge on the evolutionary connections between AGB stars and PNe.

P. Garcia-Lario

2006-05-18T23:59:59.000Z

215

Strange Quark Matter and Compact Stars  

E-Print Network [OSTI]

Astrophysicists distinguish between three different types of compact stars. These are white dwarfs, neutron stars, and black holes. The former contain matter in one of the densest forms found in the Universe which, together with the unprecedented progress in observational astronomy, make such stars superb astrophysical laboratories for a broad range of most striking physical phenomena. These range from nuclear processes on the stellar surface to processes in electron degenerate matter at subnuclear densities to boson condensates and the existence of new states of baryonic matter--like color superconducting quark matter--at supernuclear densities. More than that, according to the strange matter hypothesis strange quark matter could be more stable than nuclear matter, in which case neutron stars should be largely composed of pure quark matter possibly enveloped in thin nuclear crusts. Another remarkable implication of the hypothesis is the possible existence of a new class of white dwarfs. This article aims at giving an overview of all these striking physical possibilities, with an emphasis on the astrophysical phenomenology of strange quark matter. Possible observational signatures associated with the theoretically proposed states of matter inside compact stars are discussed as well. They will provide most valuable information about the phase diagram of superdense nuclear matter at high baryon number density but low temperature, which is not accessible to relativistic heavy ion collision experiments.

Fridolin Weber

2004-09-27T23:59:59.000Z

216

Magnetism of Herbig Ae/Be stars  

E-Print Network [OSTI]

Observations of magnetic fields of stars at the pre-main sequence phase can provide important new insights into the complex physics of the late stages of star formation. This is especially true at intermediate stellar masses, where magnetic fields are strong and globally organised, and therefore most amenable to direct study. Recent circularly-polarised spectroscopic observations of pre-main sequence Herbig Ae/Be stars have revealed the presence of organised magnetic fields in the photospheres of a small fraction of these objects. To date, 9 magnetic HAeBe stars have been detected, and those detections confirmed by repeated observations. The morphology and variability of their Stokes V signatures indicates that their magnetic fields have important dipole components of kG strength, and that the dipole is stable on timescales ofat least years. These magnetic stars exhibit a large range of stellar mass, from about 2-13 solar masses, and diverse rotational properties, with vsini from a few km/s to 200 km/s. Most ...

Wade, G A; Grunhut, J; Catala, C; Bagnulo, S; Folsom, C P; Landstreet, J D

2009-01-01T23:59:59.000Z

217

Spectroscopic variability of two Oe stars  

E-Print Network [OSTI]

The Oe stars HD45314 and HD60848 have recently been found to exhibit very different X-ray properties: whilst HD60848 has an X-ray spectrum and emission level typical of most OB stars, HD45314 features a much harder and brighter X-ray emission, making it a so-called gamma Cas analogue. Monitoring the optical spectra could provide hints towards the origin of these very different behaviours. We analyse a large set of spectroscopic observations of HD45314 and HD60848, extending over 20 years. We further attempt to fit the H-alpha line profiles of both stars with a simple model of emission line formation in a Keplerian disk. Strong variations in the strengths of the H-alpha, H-beta, and He I 5876 emission lines are observed for both stars. In the case of HD60848, we find a time lag between the variations in the equivalent widths of these lines. The emission lines are double peaked with nearly identical strengths of the violet and red peaks. The H-alpha profile of this star can be successfully reproduced by our mod...

Rauw, G; Naze, Y; Eversberg, T; Alves, F; Arnold, W; Bergmann, T; Viegas, N G Correia; Fahed, R; Fernando, A; Gonzalez-Perez, J N; Carreira, L F Gouveia; Hempelmann, A; Hunger, T; Knapen, J H; Leadbeater, R; Dias, F Marques; Mittag, M; Moffat, A F J; Reinecke, N; Ribeiro, J; Romeo, N; Gallego, J Sanchez; Santos, E M Dos; Schanne, L; Schmitt, J H M M; Schroeder, K -P; Stahl, O; Stober, Ba; Stober, Be; Vollmann, K

2015-01-01T23:59:59.000Z

218

Color superconducting quark matter in compact stars  

E-Print Network [OSTI]

Recent indications for high neutron star masses (M \\sim 2 M_sun) and large radii (R > 12 km) could rule out soft equations of state and have provoked a debate whether the occurence of quark matter in compact stars can be excluded as well. We show that modern quantum field theoretical approaches to quark matter including color superconductivity and a vector meanfield allow a microscopic description of hybrid stars which fulfill the new, strong constraints. For these objects color superconductivity turns out to be an essential ingredient for a successful description of the cooling phenomenology in accordance with recently developed tests. We discuss the energy release in the neutrino untrapping transition as a new aspect of the problem that hybrid stars masquerade themselves as neutron stars. Quark matter searches in future generations of low-temperature/high-density nucleus-nucleus collision experiments such as low-energy RHIC and CBM @ FAIR might face the same problem of an almost crossover behavior of the deconfinement transition. Therefore, diagnostic tools shall be derived from effects of color superconductivity.

D. B. Blaschke; T. Klahn; F. Sandin

2007-12-02T23:59:59.000Z

219

Hypervelocity Stars. I. The Spectroscopic Survey  

E-Print Network [OSTI]

We discuss our targeted search for hypervelocity stars (HVSs), stars traveling with velocities so extreme that dynamical ejection from a massive black hole is their only suggested origin. Our survey, now half complete, has successfully identified a total of four probable HVSs plus a number of other unusual objects. Here we report the most recently discovered two HVSs: SDSS J110557.45+093439.5 and possibly SDSS J113312.12+010824, traveling with Galactic rest-frame velocities at least +508+-12 and +418+-10 km/s, respectively. The other late B-type objects in our survey are consistent with a population of post main-sequence stars or blue stragglers in the Galactic halo, with mean metallicity [Fe/H]=-1.3 and velocity dispersion 108+-5 km/s. Interestingly, the velocity distribution shows a tail of objects with large positive velocities that may be a mix of low-velocity HVSs and high-velocity runaway stars. Our survey also includes a number of DA white dwarfs with unusually red colors, possibly extremely low mass objects. Two of our objects are B supergiants in the Leo A dwarf, providing the first spectroscopic evidence for star formation in this dwarf galaxy within the last ~30 Myr.

Warren R. Brown; Margaret J. Geller; Scott J. Kenyon; Michael J. Kurtz

2006-04-13T23:59:59.000Z

220

Quasiuniversal properties of neutron star mergers  

E-Print Network [OSTI]

Binary neutron star mergers are studied using nonlinear 3+1 numerical relativity simulations and the analytical effective-one-body (EOB) model. The EOB model predicts quasiuniversal relations between the mass-rescaled gravitational wave frequency and the binding energy at the moment of merger, and certain dimensionless binary tidal coupling constants depending on the stars Love numbers, compactnesses and the binary mass ratio. These relations are quasiuniversal in the sense that, for a given value of the tidal coupling constant, they depend significantly neither on the equation of state nor on the mass ratio, though they do depend on stars spins. The spin dependence is approximately linear for small spins aligned with the orbital angular momentum. The quasiuniversality is a property of the conservative dynamics; nontrivial relations emerge as the binary interaction becomes tidally dominated. This analytical prediction is qualitatively consistent with new, multi-orbit numerical relativity results for the relevant case of equal-mass irrotational binaries. Universal relations are thus expected to characterize neutron star mergers dynamics. In the context of gravitational wave astronomy, these universal relations may be used to constrain the neutron star equation of state using waveforms that model the merger accurately.

Sebastiano Bernuzzi; Alessandro Nagar; Simone Balmelli; Tim Dietrich; Maximiliano Ujevic

2014-06-06T23:59:59.000Z

Note: This page contains sample records for the topic "waha lone star" 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

Exploring the magnetic topologies of cool stars  

E-Print Network [OSTI]

Magnetic fields of cool stars can be directly investigated through the study of the Zeeman effect on photospheric spectral lines using several approaches. With spectroscopic measurement in unpolarised light, the total magnetic flux averaged over the stellar disc can be derived but very little information on the field geometry is available. Spectropolarimetry provides a complementary information on the large-scale component of the magnetic topology. With Zeeman-Doppler Imaging (ZDI), this information can be retrieved to produce a map of the vector magnetic field at the surface of the star, and in particular to assess the relative importance of the poloidal and toroidal components as well as the degree of axisymmetry of the field distribution. The development of high-performance spectropolarimeters associated with multi-lines techniques and ZDI allows us to explore magnetic topologies throughout the Hertzsprung-Russel diagram, on stars spanning a wide range of mass, age and rotation period. These observations b...

Morin, J; Petit, P; Albert, L; Auriere, M; Cabanac, R; Catala, C; Delfosse, X; Dintrans, B; Fares, R; Forveille, T; Gastine, T; Jardine, M; Konstantinova-Antova, R; Lanoux, J; Lignieres, F; Morgenthaler, A; Paletou, F; Velez, J C Ramirez; Solanki, S K; Theado, S; Van Grootel, V

2010-01-01T23:59:59.000Z

222

Star formation bursts in isolated spiral galaxies  

E-Print Network [OSTI]

We study the response of the gaseous component of a galactic disc to the time dependent potential generated by N-body simulations of a spiral galaxy. The results show significant variation of the spiral structure of the gas which might be expected to result in significant fluctuations in the Star Formation Rate (SFR). Pronounced local variations of the SFR are anticipated in all cases. Bursty histories for the global SFR, however, require that the mean surface density is much less (around an order of magnitude less) than the putative threshold for star formation. We thus suggest that bursty star formation histories, normally attributed to mergers and/or tidal interactions, may be a normal pattern for gas poor isolated spiral galaxies.

C. Clarke; D. Gittins

2006-07-03T23:59:59.000Z

223

SED modeling of Young Massive Stars  

E-Print Network [OSTI]

In this contribution, I review the applications and potential limitations of the spectral energy distribution fitting tool that I have developed, with a strong emphasis on the limits to which this tool can be used to improve our understanding of massive star formation. I discuss why our current grid of models cannot be used to distinguish between the several competing theories of massive star formation. I also discuss stellar mass determinations, artificial correlations between parameters in the grid of models, multiplicity, confusion, dust assumptions, and unique fits. I briefly review the improvements we intend to carry out for our next grid of models, which will eliminate many of these limitations. Finally, I show examples of applications of this tool to massive young stars.

Thomas P. Robitaille

2007-11-27T23:59:59.000Z

224

Magnetized Atmospheres around Accreting Neutron Stars  

E-Print Network [OSTI]

We present a detailed investigation of atmospheres around accreting neutron stars with high magnetic field ($B\\gtrsim 10^{12}$ G) and low luminosity ($L\\lesssim 10^{33}$ erg/s). We compute the atmospheric structure, intensity and emergent spectrum for a plane-parallel, pure hydrogen medium by solving the transfer equations for the normal modes coupled to the hydrostatic and energy balance equations. The hard tail found in previous investigations for accreting, non-magnetic neutron stars with comparable luminosity is suppressed and the X-ray spectrum, although still harder than a blackbody at the star effective temperature, is nearly planckian in shape. Spectra from accreting atmospheres, both with high and low fields, are found to exhibit a significant excess at optical wavelengths above the Rayleigh-Jeans tail of the X-ray continuum.

S. Zane; R. Turolla; A. Treves

2000-02-01T23:59:59.000Z

225

Carbon Enhanced Metal-Poor Stars. I. Chemical Compositions of 26 Stars  

E-Print Network [OSTI]

The chemical compositions of 26 metal-poor stars that exhibit strong CH and/or C2 molecular bands are determined based on high-resolution spectroscopy. We define carbon-enhanced stars taking account of the carbon abundance ratio ([C/Fe]) and the evolutionary status. Twenty two stars in our sample satisfy our modified definition for Carbon-Enhanced Metal-Poor (CEMP) stars. In addition, we measure Na abundances for nine other carbon-enhanced stars for which abundances of other elements have been previously reported. Combining our new sample with the results of previous work, we investigate the abundance and evolutionary status of a total of 64 CEMP stars. In this paper, we separate the carbon-enhanced objects into Ba-rich and Ba-normal objects, and discuss on (1) the metallicity distributions, (2) the correlation between Ba and C (and C+N) abundances, (3) C abundance distributions, (3) the distributions of evolutionary status, and (5) Na abundances. The implications of these results on the origins of carbon in CEMP stars are discussed.

Wako Aoki; Timothy C. Beers; Norbert Christlieb; John E. Norris; Sean G. Ryan; Stelios Tsangarides

2006-09-26T23:59:59.000Z

226

A new method to derive star formation histories of galaxies from their star cluster distributions  

E-Print Network [OSTI]

Star formation happens in a clustered way which is why the star cluster population of a particular galaxy is closely related to the star formation history of this galaxy. From the probabilistic nature of a mass function follows that the mass of the most-massive cluster of a complete population, M_max, has a distribution with the total mass of the population as a parameter. The total mass of the population is connected to the star formation rate (SFR) by the length of a formation epoch. Since due to evolutionary effects only massive star clusters are observable up to high ages it is convenient to use this M_max(SFR) relation for the reconstruction of a star formation history. The age-distribution of the most-massive clusters can therefore be used to constrain the star formation history of a galaxy. The method, including an assessment of the inherent uncertainties, is introduced with this contribution, while following papers will apply this method to a number of galaxies.

Thomas Maschberger; Pavel Kroupa

2007-05-07T23:59:59.000Z

227

PRECISE DOPPLER MONITORING OF BARNARD'S STAR  

SciTech Connect (OSTI)

We present 248 precise Doppler measurements of Barnard's Star (Gl 699), the second nearest star system to Earth, obtained from Lick and Keck Observatories during the 25 years between 1987 and 2012. The early precision was 20 m s{sup -1} but was 2 m s{sup -1} during the last 8 years, constituting the most extensive and sensitive search for Doppler signatures of planets around this stellar neighbor. We carefully analyze the 136 Keck radial velocities spanning 8 years by first applying a periodogram analysis to search for nearly circular orbits. We find no significant periodic Doppler signals with amplitudes above {approx}2 m s{sup -1}, setting firm upper limits on the minimum mass (Msin i) of any planets with orbital periods from 0.1 to 1000 days. Using a Monte Carlo analysis for circular orbits, we determine that planetary companions to Barnard's Star with masses above 2 M {sub Circled-Plus} and periods below 10 days would have been detected. Planets with periods up to 2 years and masses above 10 M {sub Circled-Plus} (0.03 M {sub Jup}) are also ruled out. A similar analysis allowing for eccentric orbits yields comparable mass limits. The habitable zone of Barnard's Star appears to be devoid of roughly Earth-mass planets or larger, save for face-on orbits. Previous claims of planets around the star by van de Kamp are strongly refuted. The radial velocity of Barnard's Star increases with time at 4.515 {+-} 0.002 m s{sup -1} yr{sup -1}, consistent with the predicted geometrical effect, secular acceleration, that exchanges transverse for radial components of velocity.

Choi, Jieun; Marcy, Geoffrey W.; Howard, Andrew W.; Isaacson, Howard [Department of Astronomy, University of California, Berkeley, CA 94720 (United States)] [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); McCarthy, Chris [Department of Physics and Astronomy, San Francisco State University, San Francisco, CA 94132 (United States)] [Department of Physics and Astronomy, San Francisco State University, San Francisco, CA 94132 (United States); Fischer, Debra A. [Department of Astronomy, Yale University, New Haven, CT 06520-8101 (United States)] [Department of Astronomy, Yale University, New Haven, CT 06520-8101 (United States); Johnson, John A. [Department of Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States)] [Department of Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States); Wright, Jason T., E-mail: jieun_eb@berkeley.edu [Department of Astronomy, The Pennsylvania State University, University Park, PA 16802 (United States)

2013-02-20T23:59:59.000Z

228

Effective No-Hair Relations for Neutron Stars and Quark Stars: Relativistic Results  

E-Print Network [OSTI]

Astrophysical charge-free black holes are known to satisfy no-hair relations through which all multipole moments can be specified in terms of just their mass and spin angular momentum. We here investigate the possible existence of no-hair-like relations among multipole moments for neutron stars and quark stars that are independent of their equation of state. We calculate the multipole moments of these stars up to hexadecapole order by constructing uniformly-rotating and unmagnetized stellar solutions to the Einstein equations. For slowly-rotating stars, we construct stellar solutions to quartic order in spin in a slow-rotation expansion, while for rapidly-rotating stars, we solve the Einstein equations numerically with the LORENE and RNS codes. We find that the multipole moments extracted from these numerical solutions are consistent with each other. We confirm that the current-dipole is related to the mass-quadrupole in an approximately equation of state independent fashion, which does not break for rapidly rotating neutron stars or quark stars. We further find that the current-octupole and the mass-hexadecapole moments are related to the mass-quadrupole in an approximately equation of state independent way to $\\sim 10%$, worsening in the hexadecapole case. All of our findings are in good agreement with previous work that considered stellar solutions to leading-order in a weak-field expansion. The quartic in spin, slowly-rotating solutions found here allow us to estimate the systematic errors in the measurement of the neutron star's mass and radius with future X-ray observations, such as NICER and LOFT. We find that the effect of these quartic-in-spin terms on the quadrupole and hexadecapole moments and stellar eccentricity may dominate the error budget for very rapidly-rotating neutron stars. The new universal relations found here should help to reduce such systematic errors.

Kent Yagi; Koutarou Kyutoku; George Pappas; Nicolas Yunes; Theocharis A. Apostolatos

2014-09-08T23:59:59.000Z

229

Pulsations of the R Coronae Borealis stars  

SciTech Connect (OSTI)

The radial pulsations of very luminous, low-mass models (L/M approx. 10/sup 4/, solar units), which are possible representatives of the R CrB stars, have been examined. These pulsations are extremely nonadiabatic. There are in some cases at least one extra (strange) mode which makes interpretation difficult. The blue instability edges are also peculiar, in that there is an abrupt excursion of the blue edge to the blue for L/M sufficiently large. The range of periods of the model encompasses observed periods of the Cepheid-like pulsations of actual R CrB stars.

Cox, J.P.; King, D.S.; Cox, A.N.; Wheeler, J.C.; Hansen, C.J.; Hodson, S.W.

1980-01-01T23:59:59.000Z

230

Heavy flavor production in the STAR experiment  

E-Print Network [OSTI]

In this paper, recent STAR heavy flavor measurements in proton-proton and heavy-ion collisions are highlighted. We report studies of open charm mesons, reconstructed directly from hadronic decay products, and studies of electrons from semi-leptonic decays of heavy flavor hadrons. We also present J/$\\psi$ measurements via the di-electron decay channel at various collision systems and energies. In Au+Au collisions the energy dependence of J/$\\psi$ production measured at $\\sqrt{s_{NN}}$ = 39, 62.4 and 200 GeV is shown. Finally, prospects of heavy flavor measurements with the STAR detector upgrades are discussed.

Barbara Trzeciak; for the STAR Collaboration

2014-09-11T23:59:59.000Z

231

Multiwavelength Phenomenology of Isolated Neutron Stars  

E-Print Network [OSTI]

After reviewing the multifrequency behaviour of the Isolated Neutron Stars detected so far, we analyze for each object the efficiency of conversion of the star's rotational energy loss into optical, X and gamma radiation. Although the number of pulsars detected at different wavelengths is rather limited, a pattern is seen to emerge from our analysis pointing towards the period derivative as the leading parameter to describe the multifrequency emission of INS. One object in particular, PSR 1509-58, stands out as archetypal for the Pdot-dependence of its luminosity at different wavelengths.

P. Goldoni; C. Musso; P. A. Caraveo; G. F. Bignami

1995-02-07T23:59:59.000Z

232

On the First Generation of Stars  

E-Print Network [OSTI]

We argue that the first stars may have spanned the conventional mass range rather than be identified with the Very Massive Objects (100-1000 solar masses) favoured by numerical simulations. Specifically, we find that magnetic field generation processes acting in the first protostellar systems suffice to produce fields that exceed the threshold for MRI instability to operate and thereby allow the MRI dynamo to generate equipartition-amplitude magnetic fields on protostellar mass scales below 50 solar masses. Such fields allow primordial star formation to occur at essentially any metallicity by regulating angular momentum transfer, fragmentation, accretion and feedback in much the same way as occurs in conventional molecular clouds.

Joseph Silk; Mathieu Langer

2006-06-12T23:59:59.000Z

233

Mathematical Modelling of Tyndall Star Initiation  

E-Print Network [OSTI]

The superheating that usually occurs when a solid is melted by volumetric heating can produce irregular solid/liquid interfaces. Such interfaces can be visualised in ice, where they are sometimes known as Tyndall stars. This paper describes some of the experimental observations of Tyndall stars and a mathematical model for the early stages of their evolution. The modelling is complicated by the strong crystalline anisotropy, which results in an anisotropic kinetic undercooling at the interface, and it leads to an interesting class of codimension-2 free boundary problems.

Harvey, Peter; Katz, Richard F; Lacey, Andrew A

2015-01-01T23:59:59.000Z

234

Star Power | Princeton Plasma Physics Lab  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr MayAtmosphericNuclear Security Administrationcontroller systemsBiSiteNeutron Scattering4 ByWatching IonsStar Power Star Power The

235

Conversion of neutron stars to strange stars as the central engine of gamma-ray bursts  

E-Print Network [OSTI]

We study the conversion of a neutron star to a strange star as a possible energy source for gamma-ray bursts. We use different recent models for the equation of state of neutron star matter and strange quark matter. We show that the total amount of energy liberated in the conversion is in the range of (1-4) 10^{53} ergs (one order of magnitude larger than previous estimates) and is in agreement with the energy required to power gamma-ray burst sources at cosmological distances.

Ignazio Bombaci; Bhaskar Datta

2000-01-27T23:59:59.000Z

236

Gamma-Ray Bursts and Afterglows from Rotating Strange Stars and Neutron Stars  

E-Print Network [OSTI]

We here discuss a new model of $\\gamma$-ray bursts (GRBs) based on differentially rotating strange stars. Strange stars in this model and differentially rotating neutron stars in the Klu\\'zniak-Ruderman model can produce extremely relativistic, variable fireballs required by GRBs and then become millisecond pulsars. The effect of such pulsars on expansion of the postburst fireballs through magnetic dipole radiation is studied. We show that these two models can explain naturally not only various features of GRBs but also light curves of afterglows.

Z. G. Dai; T. Lu

1998-10-21T23:59:59.000Z

237

Perlick: ENERGY STAR Referral (HP48RO-S)  

Broader source: Energy.gov [DOE]

DOE referred Perlick refrigerator HP48RO-S to EPA, brand manager of the ENERGY STAR program, for appropriate action after DOE testing revealed that the model does not meet ENERGY STAR requirements.

238

CORONAL ABUNDANCES IN ORION NEBULA CLUSTER STARS A. Maggio,1  

E-Print Network [OSTI]

pattern of abundances for all stars, although a weak dependence on flare loop size may be present. The abundance of calcium is the only one which appears to vary substantially between stars, but this quantity

Micela, Giusi

239

Probing young massive clusters with laser guide star adaptive optics  

E-Print Network [OSTI]

laser guide star adaptive optics Nate McCrady Received: 10laser guide star adaptive optics (LGS/AO) on the 10 m Keckof 4 Mpc. Our adaptive optics work is motivated by three

McCrady, Nate

2009-01-01T23:59:59.000Z

240

Hitting the Target: ENERGY STAR® SSL Outdoor Area Lighting Webcast  

Broader source: Energy.gov [DOE]

In this October 8, 2009 webcast, ENERGY STAR Program Manager Richard Karney gave an overview of ENERGY STAR criteria covering SSL-based outdoor area and roadway lighting, outdoor wall packs,...

Note: This page contains sample records for the topic "waha lone star" 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

Haier: ENERGY STAR Referral (ESA408J) | Department of Energy  

Broader source: Energy.gov (indexed) [DOE]

ESA408J) Haier: ENERGY STAR Referral (ESA408J) March 4, 2011 DOE referred Haier room air conditioner model ESA408J to EPA, brand manager of the ENERGY STAR program, for appropriate...

242

Grant County PUD- EnergyStar New Home Certification Program  

Broader source: Energy.gov [DOE]

Grant County PUD offers incentives to qualifying customers through the Energy Star Home Certification Program. The Energy Star certification is available for both new site-built homes and new...

243

ENERGY STAR Jeopardy History Facts Universities Products Other  

E-Print Network [OSTI]

ENERGY STAR Jeopardy History Facts Universities Products Other 10 10 10 10 10 20 20 20 20 20 30 30 30 30 30 40 40 40 40 40 50 50 50 50 50 #12;In what year did ENERGY STAR start? A)2002 B)2008 C)1992 D)1999 #12;Answer: C) 1992! In 1992 the US Environmental Protection Agency (EPA) introduced ENERGY STAR

Brownstone, Rob

244

Planet-Star Plasma Interactions and Possible Radio Emission  

E-Print Network [OSTI]

? · Planetary radio emissions properties & energy source in Planet-Star plasma interactions · Scaling laws contraints on scaling laws & internal structure models Comparative magnetospheric physics (star-planet properties & energy source in Planet-Star plasma interactions · Scaling laws and Extrapolation to hot

Demoulin, Pascal

245

Creating an intelligent agent for StarCraft: Brood War  

E-Print Network [OSTI]

Creating an intelligent agent for StarCraft: Brood War University of Liège Faculty of Applied artificialintelligence (AI)? Video games Why real-time strategy (RTS) games? Introduction #12;StarCraft: Brood War a patrol unit #12;Implementation Chapter III #12;StarCraft is not open source! The Brood War Application

Ernst, Damien

246

STAR-FREE GEODESIC LANGUAGES FOR GROUPS SUSAN HERMILLER1  

E-Print Network [OSTI]

STAR-FREE GEODESIC LANGUAGES FOR GROUPS SUSAN HERMILLER1 , DEREK F. HOLT, AND SARAH REES Abstract cancellation con- ditions C (1/6) and C (1/4) - T (4) has the property that the set of all geodesics (over the same generating set) is a star-free regular language. Star-free regularity of the geodesic set is shown

Logan, David

247

THE Be STAR SPECTRA (BeSS) DATABASE  

SciTech Connect (OSTI)

Be stars vary on many timescales, from hours to decades. A long time base of observations to analyze certain phenomena in these stars is therefore necessary. Collecting all existing and future Be star spectra into one database has thus emerged as an important tool for the Be star community. Moreover, for statistical studies, it is useful to have centralized information on all known Be stars via an up-to-date catalog. These two goals are what the Be Star Spectra (BeSS, http://basebe.obspm.fr) database proposes to achieve. The database contains an as-complete-as-possible catalog of known Be stars with stellar parameters, as well as spectra of Be stars from all origins (any wavelength, any epoch, any resolution, etc.). It currently contains over 54,000 spectra of more than 600 different Be stars among the {approx}2000 Be stars in the catalog. A user can access and query this database to retrieve information on Be stars or spectra. Registered members can also upload spectra to enrich the database. Spectra obtained by professional as well as amateur astronomers are individually validated in terms of format and science before being included in BeSS. In this paper, we present the database itself as well as examples of the use of BeSS data in terms of statistics and the study of individual stars.

Neiner, C.; De Batz, B. [LESIA, UMR 8109 du CNRS, Observatoire de Paris, UPMC, Univ. Paris Diderot, 92195 Meudon Cedex (France); Cochard, F. [Shelyak Instruments, Les Roussets, 38420 Revel (France); Floquet, M.; Mekkas, A. [GEPI, UMR 8111 du CNRS, Observatoire de Paris, Univ. Paris Diderot, 92195 Meudon Cedex (France); Desnoux, V., E-mail: coralie.neiner@obspm.fr [ARAS, Astronomical Ring for Access to Spectroscopy (Country Unknown)

2011-11-15T23:59:59.000Z

248

Hot neutron star in generalized thermo-statistics  

E-Print Network [OSTI]

Hot neutron star in generalized thermo-statistics K. Miyazaki E-mail: miyazakiro@rio.odn.ne.jp Abstract The hot neutron star (NS) is investigated for the ...rst time in the generalized thermo-statistics. The study of neutron star (NS) is an important subject in nuclear physics and astro- physics. The equation

249

Energy star compliant voice over internet protocol (VoIP) telecommunications network including energy star compliant VoIP devices  

DOE Patents [OSTI]

A Voice over Internet Protocol (VoIP) communications system, a method of managing a communications network in such a system and a program product therefore. The system/network includes an ENERGY STAR (E-star) aware softswitch and E-star compliant communications devices at system endpoints. The E-star aware softswitch allows E-star compliant communications devices to enter and remain in power saving mode. The E-star aware softswitch spools messages and forwards only selected messages (e.g., calls) to the devices in power saving mode. When the E-star compliant communications devices exit power saving mode, the E-star aware softswitch forwards spooled messages.

Kouchri, Farrokh Mohammadzadeh

2012-11-06T23:59:59.000Z

250

EPA ENERGY STAR Webinar: The Federal Guiding Principles Checklist in ENERGY STAR Portfolio  

Broader source: Energy.gov [DOE]

Hosted by the EPA, this webinar will focus on how to use the ENERGY STAR measurement and tracking tool, Portfolio Manager, to help ensure compliance with the Guiding Principles for High Performance Sustainable Buildings.

251

The Texas LoanSTAR Program: Acquiring and Archiving LoanSTAR Data  

E-Print Network [OSTI]

This paper discusses the acquisition and archiving of data for the Texas LoanSTAR monitoring program, an eight year, $98 million revolving loan program for energy conservation retrofits in Texas state, local government and school buildings funded...

Haberl, J. S.; Katipamula, S.; Willis, D.; Weber, K.; Matson, J.; Rayaprolu, M.; Subramanian, U.

1990-01-01T23:59:59.000Z

252

Model study of a quark star  

SciTech Connect (OSTI)

In this paper we apply the equation of state (EOS) of QCD at finite chemical potential and zero temperature proposed in H. S. Zong and W. M. Sun [Int. J. Mod. Phys. A 23, 3591 (2008)] to the study of properties of quark star. This EOS contains only one adjustable parameter m{sub D} which sets the scale of chiral symmetry breaking (in our calculation we have chosen two values of m{sub D}: m{sub D}=244 MeV and m{sub D}=239 MeV, which is fitted from the value of f{sub {pi}} and determined by e{sup +}e{sup -} annihilation experiment, respectively). From this EOS a model of quark star is established by applying the Tolman-Oppenheimer-Volkoff equation under two conditions: with the P({mu}=0) term and without the P({mu}=0) term. Our results show clearly that the P({mu}=0) term is an important quantity in the study of quark star. A comparison between our model and other models of quark star is made. In particular, we have compared our results with the most recent observational data measured using Shapiro delay reported in P. B. Demorest et al.[Nature (London) 467, 1081 (2010)].

Li Hua; Jiang Yu [Department of Physics, Nanjing University, Nanjing 210093 (China); Luo Xinlian [Department of Astronomy, Nanjing University, Nanjing 210093 (China); Zong Hongshi [Department of Physics, Nanjing University, Nanjing 210093 (China); Joint Center for Particle, Nuclear Physics and Cosmology, Nanjing 210093 (China)

2011-01-15T23:59:59.000Z

253

Hypersonic Molecular Shocks in Star Forming Regions  

E-Print Network [OSTI]

Much emission from star forming regions is from shock-excited gas. Shocks in molecular clouds are still not fully understood, as magnetic fields, dust and chemistry all play significant roles. I review the history, physics and current work in understanding these shocks, and in their possible use as diagnostics of local conditions.

Brand, P W J L

2006-01-01T23:59:59.000Z

254

Hypersonic Molecular Shocks in Star Forming Regions  

E-Print Network [OSTI]

Much emission from star forming regions is from shock-excited gas. Shocks in molecular clouds are still not fully understood, as magnetic fields, dust and chemistry all play significant roles. I review the history, physics and current work in understanding these shocks, and in their possible use as diagnostics of local conditions.

Peter W. J. L. Brand

2006-09-08T23:59:59.000Z

255

Boson stars from a gauge condensate  

E-Print Network [OSTI]

The boson star filled with two interacting scalar fields is investigated. The scalar fields can be considered as a gauge condensate formed by SU(3) gauge field quantized in a non-perturbative manner. The corresponding solution is regular everywhere, has a finite energy and can be considered as a quantum SU(3) version of the Bartnik - McKinnon particle-like solution.

V. Dzhunushaliev; K. Myrzakulov; R. Myrzakulov

2006-12-28T23:59:59.000Z

256

Massive stars in their death-throes  

E-Print Network [OSTI]

The study of the stars that explode as supernovae used to be a forensic study, working backwards from the remnants of the star. This changed in 1987 when the first progenitor star was identified in pre-explosion images. Currently there are 8 detected progenitors with another 21 non-detections, for which only a limit on the pre-explosion luminosity can be placed. This new avenue of supernova research has led to many interesting conclusions, most importantly that the progenitors of the most common supernovae, type IIP, are red supergiants as theory has long predicted. However no progenitors have been detected thus far for the hydrogen-free type Ib/c supernovae which, given the expected progenitors, is an unlikely result. Also observations have begun to show evidence that luminous blue variables, which are among the most massive stars, may directly explode as supernovae. These results contradict current stellar evolution theory. This suggests that we may need to update our understanding.

J. J. Eldridge

2008-09-11T23:59:59.000Z

257

ANALYTICAL STAR FORMATION RATE FROM GRAVOTURBULENT FRAGMENTATION  

SciTech Connect (OSTI)

We present an analytical determination of the star formation rate (SFR) in molecular clouds, based on a time-dependent extension of our analytical theory of the stellar initial mass function. The theory yields SFRs in good agreement with observations, suggesting that turbulence is the dominant, initial process responsible for star formation. In contrast to previous SFR theories, the present one does not invoke an ad hoc density threshold for star formation; instead, the SFR continuously increases with gas density, naturally yielding two different characteristic regimes, thus two different slopes in the SFR versus gas density relationship, in agreement with observational determinations. Besides the complete SFR derivation, we also provide a simplified expression, which reproduces the complete calculations reasonably well and can easily be used for quick determinations of SFRs in cloud environments. A key property at the heart of both our complete and simplified theory is that the SFR involves a density-dependent dynamical time, characteristic of each collapsing (prestellar) overdense region in the cloud, instead of one single mean or critical freefall timescale. Unfortunately, the SFR also depends on some ill-determined parameters, such as the core-to-star mass conversion efficiency and the crossing timescale. Although we provide estimates for these parameters, their uncertainty hampers a precise quantitative determination of the SFR, within less than a factor of a few.

Hennebelle, Patrick [Laboratoire de Radioastronomie, UMR CNRS 8112, Ecole Normale Superieure et Observatoire de Paris, 24 rue Lhomond, 75231 Paris Cedex 05 (France); Chabrier, Gilles [Ecole Normale Superieure de Lyon, CRAL, UMR CNRS 5574, 69364 Lyon Cedex 07 (France)

2011-12-20T23:59:59.000Z

258

"The Stars Tonight" LIVE Planetarium Show  

E-Print Network [OSTI]

wasn't turning around us, rather the Earth is turning on its axis. S B5: Conservation of Energy and city lights. Many NASM visitors have never had the chance to see a dark sky, with the stars on display of technology to enhance gathering and manipulation of data, the accuracy/precision of data gathering

Mathis, Wayne N.

259

EPA Natural Gas STAR Program Accomplishments  

E-Print Network [OSTI]

Established in 1993, the Natural Gas STAR program is a partnership between the U.S. EPA and the oil and natural gas industry designed to cost-effectively reduce methane emissions from voluntary activities undertaken at oil and natural gas operations both

unknown authors

260

Singularity-free dark energy star  

E-Print Network [OSTI]

We propose a model for an anisotropic dark energy star where we assume that the radial pressure exerted on the system due to the presence of dark energy is proportional to the isotropic perfect fluid matter density. We discuss various physical features of our model and show that the model satisfies all the regularity conditions and stable as well as singularity-free.

Farook Rahaman; Anil Kumar Yadav; Saibal Ray; Raju Maulick; Ranjan Sharma

2011-08-25T23:59:59.000Z

Note: This page contains sample records for the topic "waha lone star" 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

Life Extinction Due To Neutron Star Mergers  

E-Print Network [OSTI]

Cosmic ray bursts (CRBs) from mergers or accretion induced collapse of neutron stars that hit an Earth-like planet closer than $\\sim 1 kpc$ from the explosion produce lethal fluxes of atmospheric muons at ground level, underground and underwater. These CRBs also destroy the ozone layer and radioactivate the environment. The mean rate of such life devastating CRBs is one in 100 million years (Myr), consistent with the observed 5 ``great'' extinctions in the past 600 Myr. Unlike the previously suggested extraterrestrial extinction mechanisms the CRBs explain massive life extinction on the ground, underground and underwater and the higher survival levels of radiation resistant species and of terrain sheltered species. More distant mergers can cause smaller extinctions. Biological mutations caused by ionizing radiation produced by the CRB may explain a fast appearance of new species after mass extinctions. The CRB extinction predicts detectable enrichment of rock layers which formed during the extinction periods with cosmogenically produced radioactive nucleides such as $^{129}$I, $^{146}$Sm, $^{205}$Pb with and $^{244}$Pu. Tracks of high energy particles in rock layers on Earth and on the moon may also contain records of intense CRBs. An early warning of future extinctions due to neutron star mergers can be obtained by identifying, mapping and timing all the nearby binary neutron stars systems. A final warning of an approaching CRB from a nearby neutron stars merger will be provided by a gamma ray burst a few days before the arrival of the CRB.

Arnon Dar; Ari Laor; Nir J. Shaviv

1996-11-24T23:59:59.000Z

262

Solid Waste Diversion Plan Fallen Star, 2012  

E-Print Network [OSTI]

Solid Waste Diversion Plan DO HO DUH Fallen Star, 2012 Stuart Collection UC San Diego Updated July 2012 Prepared by: Facilities Management #12;UC San Diego Solid Waste Diversion Plan Table of Contents Overview Location and Areas Covered Recycling and Solid Waste Management Contact Campus/Medical Center

Aluwihare, Lihini

263

Neutron star interiors and topology change  

E-Print Network [OSTI]

Quark matter is believed to exist in the center of neutron stars. A combined model consisting of quark matter and ordinary matter is used to show that the extreme conditions existing in the center could result in a topology change, that is, in the formation of wormholes.

Peter K. F. Kuhfittig

2012-07-27T23:59:59.000Z

264

A CATALOG OF GALACTIC INFRARED CARBON STARS  

SciTech Connect (OSTI)

We collected almost all of the Galactic infrared carbon stars (IRCSs) from literature published up to the present to organize a catalog of 974 Galactic IRCSs in this paper. Some of their photometric properties in the near-, mid-, and far-infrared are discussed.

Chen, P. S. [National Astronomical Observatories/Yunnan Observatory and Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, Kunming 650011 (China); Yang, X. H., E-mail: iraspsc@yahoo.com.cn, E-mail: yangxh@cqu.edu.cn [Department of Physics, Chongqing University, Chongqing 400044 (China)

2012-02-15T23:59:59.000Z

265

Constraints in the coupling Star-Life  

E-Print Network [OSTI]

If life is sustained by a process of photosynthesis, not necessarily the same existing on Earth, the surface temperature of the star and the orbit of the host planet cannot be whatsoever. In fact the global life cycle, no matter how complicated, must contain in general an upper photochemical branch and a lower dark branch, characterized by a higher and a lower temperature. These two temperatures are star-orbit related. The velocity along the cycle or, in other words, the power of the life machine, depends in general on several other parameters. First of all the Gibbs photon availability, which is a star-orbit parameter and is the input for the upper branch. Then follows the energy cascade that develops along the organic web with a large number of interactions and typical times that must match the typical times generated by the combination of spin value and orientation, eccentricity and precession. Finally, the capacity of the web to keep the global life cycle running along the life span of the star, comes from some inner form of self-endurance and self-balance. The property of not being transient could be the right way of introducing the concept of intelligent life.

L. Sertorio; G. Tinetti

2001-10-01T23:59:59.000Z

266

Galactic structure studies with BATC star counts  

E-Print Network [OSTI]

We report the first results of star counts carried out with the National Astronomical Observatories (NAOC) 60/90 cm Schmidt Telescope in 15 intermediate-band filters from 3000 to 10000 {\\AA} in the BATC survey. We analyze a sample of over 1400 main sequence stars ($14\\le$V$\\le21$), which lie in the field with central coordinates R.A.=$09^h53^m13^s.30$ and DEC=47$^\\circ49^{\\prime}00^{\\prime\\prime}.0$ (J2000). The field of view is 0.95 deg$^{2}$, and the spatial scale was $1\\arcsec.67$. In our model, the distribution of stars perpendicular to the plane of the Galaxy is given by two exponential disks (thin disk plus thick disk) and a de Vaucouleurs halo. Based on star counts, we derive the scale heights of the thin disk to be $320^{+14}_{-15}$ pc and of the thick disk to be $640^{+30}_{-32}$ pc, respectively, with a local density of $7.0\\pm1%$ of the thin disk. We find that the observed counts support an axial ratio of $c/a\\le0.6$ for a de Vaucouleurs $r^{1/4}$ law, implying a more flattened halo. We also derive...

Du, C; Ma, J; Chen, A B C; Yang, Y; Li, J; Wu, H; Jiang, Z; Chen, J; Du, Cuihua; Zhou, Xu; Ma, Jun; Chen, Alfred B-C; Yang, Yanbin; Li, Jiuli; Wu, Hong; Jiang, Zhaoji; Chen, Jiansheng

2003-01-01T23:59:59.000Z

267

Stellar Content and Star Formation Histories  

E-Print Network [OSTI]

The evolution of irregular galaxies is examined from two points of view: on the one hand, models of galactic chemical evolution have been computed and their predictions compared with the corresponding observational data on the element abundances, and on the other hand, the results of a new method to derive the star formation history in the last 1 Gyr in nearby irregulars are presented.

M. Tosi

1993-12-14T23:59:59.000Z

268

Flux Expulsion - Field Evolution in Neutron Stars  

E-Print Network [OSTI]

Models for the evolution of magnetic fields of neutron stars are constructed, assuming the field is embedded in the proton superconducting core of the star. The rate of expulsion of the magnetic flux out of the core, or equivalently the velocity of outward motion of flux-carrying proton-vortices is determined from a solution of the Magnus equation of motion for these vortices. A force due to the pinning interaction between the proton-vortices and the neutron-superfluid vortices is also taken into account in addition to the other more conventional forces acting on the proton-vortices. Alternative models for the field evolution are considered based on the different possibilities discussed for the effective values of the various forces. The coupled spin and magnetic evolution of single pulsars as well as those processed in low-mass binary systems are computed, for each of the models. The predicted lifetimes of active pulsars, field strengths of the very old neutron stars, and distribution of the magnetic fields versus orbital periods in low-mass binary pulsars are used to test the adopted field decay models. Contrary to the earlier claims, the buoyancy is argued to be the dominant driving cause of the flux expulsion, for the single as well as the binary neutron stars. However, the pinning is also found to play a crucial role which is necessary to account for the observed low field binary and millisecond pulsars.

M. Jahan-Miri

1999-10-27T23:59:59.000Z

269

Gravitational lensing by stars with angular momentum  

E-Print Network [OSTI]

Gravitational lensing by spinning stars, approximated as homogeneous spheres, is discussed in the weak field limit. Dragging of inertial frames, induced by angular momentum of the deflector, breaks spherical symmetry. I examine how the gravito-magnetic field affects image positions, caustics and critical curves. Distortion in microlensing-induced light curves is also considered.

M. Sereno

2003-07-11T23:59:59.000Z

270

Gamma Ray Bursts from delayed collapse of neutron stars to quark matter stars  

E-Print Network [OSTI]

We propose a model to explain how a Gamma Rays Burst can take place days or years after a supernova explosion. Our model is based on the conversion of a pure hadronic star (neutron star) into a star made at least in part of deconfined quark matter. The conversion process can be delayed if the surface tension at the interface between hadronic and deconfined-quark-matter phases is taken into account. The nucleation time (i.e. the time to form a critical-size drop of quark matter) can be extremely long if the mass of the star is small. Via mass accretion the nucleation time can be dramaticaly reduced and the star is finally converted into the stable configuration. A huge amount of energy, of the order of 10$^{52}$--10$^{53}$ erg, is released during the conversion process and can produce a powerful Gamma Ray Burst. The delay between the supernova explosion generating the metastable neutron star and the new collapse can explain the delay proposed in GRB990705 and in GRB011211.

Berezhiani, Z G; Drago, A; Frontera, F; Lavagno, A

2003-01-01T23:59:59.000Z

271

Gamma Ray Bursts from delayed collapse of neutron stars to quark matter stars  

E-Print Network [OSTI]

We propose a model to explain how a Gamma Rays Burst can take place days or years after a supernova explosion. Our model is based on the conversion of a pure hadronic star (neutron star) into a star made at least in part of deconfined quark matter. The conversion process can be delayed if the surface tension at the interface between hadronic and deconfined-quark-matter phases is taken into account. The nucleation time (i.e. the time to form a critical-size drop of quark matter) can be extremely long if the mass of the star is small. Via mass accretion the nucleation time can be dramaticaly reduced and the star is finally converted into the stable configuration. A huge amount of energy, of the order of 10$^{52}$--10$^{53}$ erg, is released during the conversion process and can produce a powerful Gamma Ray Burst. The delay between the supernova explosion generating the metastable neutron star and the new collapse can explain the delay proposed in GRB990705 and in GRB011211.

Z. Berezhiani; I. Bombaci; A. Drago; F. Frontera; A. Lavagno

2003-02-13T23:59:59.000Z

272

LIMITING ACCRETION ONTO MASSIVE STARS BY FRAGMENTATION-INDUCED STARVATION  

SciTech Connect (OSTI)

Massive stars influence their surroundings through radiation, winds, and supernova explosions far out of proportion to their small numbers. However, the physical processes that initiate and govern the birth of massive stars remain poorly understood. Two widely discussed models are monolithic collapse of molecular cloud cores and competitive accretion. To learn more about massive star formation, we perform and analyze simulations of the collapse of rotating, massive, cloud cores including radiative heating by both non-ionizing and ionizing radiation using the FLASH adaptive-mesh refinement code. These simulations show fragmentation from gravitational instability in the enormously dense accretion flows required to build up massive stars. Secondary stars form rapidly in these flows and accrete mass that would have otherwise been consumed by the massive star in the center, in a process that we term fragmentation-induced starvation. This explains why massive stars are usually found as members of high-order stellar systems that themselves belong to large clusters containing stars of all masses. The radiative heating does not prevent fragmentation, but does lead to a higher Jeans mass, resulting in fewer and more massive stars than would form without the heating. This mechanism reproduces the observed relation between the total stellar mass in the cluster and the mass of the largest star. It predicts strong clumping and filamentary structure in the center of collapsing cores, as has recently been observed. We speculate that a similar mechanism will act during primordial star formation.

Peters, Thomas; Klessen, Ralf S.; Banerjee, Robi [Institut fuer Theoretische Astrophysik, Zentrum fuer Astronomie der Universitaet Heidelberg, Albert-Ueberle-Str. 2, D-69120 Heidelberg (Germany); Low, Mordecai-Mark Mac, E-mail: thomas.peters@ita.uni-heidelberg.d [Department of Astrophysics, American Museum of Natural History, 79th Street at Central Park West, New York, NY 10024-5192 (United States)

2010-12-10T23:59:59.000Z

273

Magnetic topologies of the Herbig Ae/Be stars  

E-Print Network [OSTI]

Our recent discoveries of magnetic fields in a small number of Herbig Ae/Be (HAeBe) stars, the evolutionary progenitors of main sequence A/B stars, raise new questions about the origin of magnetic fields in the intermediate mass stars. The favoured fossil field hypothesis suggests that a few percent of magnetic pre-main sequence A/B stars should exhibit similar magnetic strengths and topologies to the magnetic Ap/Bp stars. In this talk I will present the methods that we have used to characterise the magnetic fields of the Herbig Ae/Be stars, as well as our first conclusions on the origin of magnetism in intermediate-mass stars.

Alecian, E; Catala, C; Bagnulo, S; Böhm, T; Bouret, J -C; Donati, J -F; Folsom, C; Grunhut, J; Landstreet, J D; Petit, P; Silvester, J

2008-01-01T23:59:59.000Z

274

Hypervelocity binary stars: smoking gun of massive binary black holes  

E-Print Network [OSTI]

The hypervelocity stars recently found in the Galactic halo are expelled from the Galactic center through interactions between binary stars and the central massive black hole or between single stars and a hypothetical massive binary black hole. In this paper, we demonstrate that binary stars can be ejected out of the Galactic center with velocities up to 10^3 km/s, while preserving their integrity, through interactions with a massive binary black hole. Binary stars are unlikely to attain such high velocities via scattering by a single massive black hole or through any other mechanisms. Based on the above theoretical prediction, we propose a search for binary systems among the hypervelocity stars. Discovery of hypervelocity binary stars, even one, is a definitive evidence of the existence of a massive binary black hole in the Galactic center.

Youjun Lu; Qingjuan Yu; D. N. C. Lin

2007-07-22T23:59:59.000Z

275

Laser Guide Star Adaptive Optics without Tip-tilt  

E-Print Network [OSTI]

Adaptive optics (AO) systems allow a telescope to reach its diffraction limit at near infrared wavelengths. But to achieve this, a bright natural guide star (NGS) is needed for the wavefront sensing, severely limiting the fraction of the sky over which AO can be used. To some extent this can be overcome with a laser guide star (LGS). While the laser can be pointed anywhere in the sky, one still needs to have a natural star, albeit fainter, reasonably close to correct the image motion (tip-tilt) to which laser guide stars are insensitive. There are in fact many astronomical targets without suitable tip-tilt stars, but for which the enhanced resolution obtained with the Laser Guide Star Facility (LGSF) would still be very beneficial. This article explores what adaptive optics performance one might expect if one dispenses with the tip-tilt star, and in what situations this mode of observing might be needed.

R. Davies; S. Rabien; C. Lidman; M. Le Louarn; M. Kasper; N. M. Forster Schreiber; V. Roccatagliata; N. Ageorges; P. Amico; C. Dumas; F. Mannucci

2008-01-24T23:59:59.000Z

276

The MACHO Project LMC Variable Star Inventory; 4, Multimode RR Lyrae Stars, Distance to the LMC and Age of the Oldest Stars  

E-Print Network [OSTI]

We report the discovery of 73 double-mode RR Lyrae (RRd) stars in fields near the bar of the LMC. The stars are detected among the MACHO database of short-period variables that currently contains about 7900 RR Lyrae stars. Fundamental periods (P_0) for these stars are found in the range 0.46-0.55 days and first overtone-to-fundamental period ratios are found to be in the range 0.742 FBE) of the instability strip. Comparison of the calibrated MACHO V and R_KC photometry with these derived absolute magnitudes yields an absorption-corrected distan...

Alcock, C B; Alves, D R; Axelrod, T S; Becker, A C; Bennett, D P; Cook, K H; Freeman, K C; Griest, K; Guern, J A; Lehner, M J; Marshall, S L; Minniti, D; Peterson, B A; Pratt, M R; Quinn, P J; Rodgers, A W; Sutherland, W; Welch, D L

1996-01-01T23:59:59.000Z

277

Constraining the neutron star equation of state with gravitational wave signals from coalescing binary neutron stars  

E-Print Network [OSTI]

Recently exploratory studies were performed on the possibility of constraining the neutron star equation of state (EOS) using signals from coalescing binary neutron stars, or neutron star-black hole systems, as they will be seen in upcoming advanced gravitational wave detectors such as Advanced LIGO and Advanced Virgo. In particular, it was estimated to what extent the combined information from multiple detections would enable one to distinguish between different equations of state through hypothesis ranking or parameter estimation. Under the assumption of zero neutron star spins both in signals and in template waveforms and considering tidal effects to 1PN order, it was found that O(20) sources would suffice to distinguish between a hard, moderate, and soft equation of state. Here we revisit these results, this time including neutron star tidal effects to the highest order currently known, termination of gravitational waveforms at the contact frequency, neutron star spins, and the resulting quadrupole-monopole interaction. We also take the masses of neutron stars in simulated sources to be distributed according to a relatively strongly peaked Gaussian, as hinted at by observations, but without assuming that the data analyst will necessarily have accurate knowledge of this distribution for use as a mass prior. We find that especially the effect of the latter is dramatic, necessitating many more detections to distinguish between different EOS and causing systematic biases in parameter estimation, on top of biases due to imperfect understanding of the signal model pointed out in earlier work. This would get mitigated if reliable prior information about the mass distribution could be folded into the analyses.

Michalis Agathos; Jeroen Meidam; Walter Del Pozzo; Tjonnie G. F. Li; Marco Tompitak; John Veitch; Salvatore Vitale; Chris Van Den Broeck

2015-03-18T23:59:59.000Z

278

Towards a metallurgy of neutron star crusts  

E-Print Network [OSTI]

In the standard picture of the crust of a neutron star, matter there is simple: a body-centered-cubic (bcc) lattice of nuclei immersed in an essentially uniform electron gas. We show that at densities above that for neutron drip ($\\sim4\\times10^11$) g cm$^{-3}$ or roughly one thousandth of nuclear matter density, the interstitial neutrons give rise to an attractive interaction between nuclei that renders the lattice unstable. We argue that the likely equilibrium structure is similar to that in displacive ferroelectric materials such as BaTiO$_3$. As a consequence, properties of matter in the inner crust are expected to be much richer than previously appreciated and we mention consequences for observable neutron star properties.

Kobyakov, D

2013-01-01T23:59:59.000Z

279

Towards a metallurgy of neutron star crusts  

E-Print Network [OSTI]

In the standard picture of the crust of a neutron star, matter there is simple: a body-centered-cubic (bcc) lattice of nuclei immersed in an essentially uniform electron gas. We show that at densities above that for neutron drip ($\\sim4\\times10^11$) g cm$^{-3}$ or roughly one thousandth of nuclear matter density, the interstitial neutrons give rise to an attractive interaction between nuclei that renders the lattice unstable. We argue that the likely equilibrium structure is similar to that in displacive ferroelectric materials such as BaTiO$_3$. As a consequence, properties of matter in the inner crust are expected to be much richer than previously appreciated and we mention consequences for observable neutron star properties.

D. Kobyakov; C. J. Pethick

2013-09-07T23:59:59.000Z

280

Forming equatorial rings around dying stars  

E-Print Network [OSTI]

We suggest that clumpy-dense outflowing equatorial rings around evolved giant stars, such as in supernova 1987A and the Necklace planetary nebula, are formed by bipolar jets that compress gas toward the equatorial plane. The jets are launched from an accretion disk around a stellar companion. Using the FLASH hydrodynamics numerical code we perform 3D numerical simulations, and show that bipolar jets expanding into a dense spherical shell can compress gas toward the equatorial plane and lead to the formation of an expanding equatorial ring. Rayleigh-Taylor instabilities in the interaction region break the ring to clumps. Under the assumption that the same ring-formation mechanism operates in massive stars and in planetary nebulae, we find this mechanism to be more promising for ring formation than mass loss through the second Lagrangian point. The jets account also for the presence of a bipolar nebula accompanying many of the rings.

Akashi, Muhammad; Yogev, Ohad; Soker, Noam

2015-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "waha lone star" 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

NLTE wind models for SMC stars  

E-Print Network [OSTI]

We study stellar wind properties of selected late O stars in the Small Magellanic Cloud (SMC). We calculate NLTE line-driven wind models for these stars and compare predicted wind parameters with observed values. We found satisfactory agreement between theoretical and observed terminal velocities. On the other hand, predicted and observed mass-loss rates are in a good agreement only for higher mass-loss rates. For mass-loss rates lower than approximately 10^{-7} M_sun / year we found large discrepancy between theoretical and observed values. We propose a new explanation of this effect based on dynamical decoupling of some atoms. Finally, we study the dependence of wind terminal velocities and mass-loss rates on metallicity.

Jiri Krticka

2005-09-15T23:59:59.000Z

282

Supergiant Pulses from Extragalactic Neutron Stars  

E-Print Network [OSTI]

We evaluate the hypothesis that extragalactic radio bursts originate from neutron stars. These could be active pulsars or dormant, slowly spinning objects, but the different population distances for these two classes require correspondingly different contributions to burst dispersion measures from any host or intervening galaxies combined with the intergalactic medium. The large, apparent burst rate $\\sim 10^4~$ sky$^{-1}~$ day$^{-1}$ is comparable to the core-collapse supernova rate in a Hubble volume and can be accommodated by a single burst per object in the resulting large reservoir of $\\sim 10^{17}~$ neutron stars. A smaller population distance requires more bursts per object but the likelihood of seeing repeated bursts from any single object is extremely low on human timescales. Gravitational microlensing could play a role for high redshift sources. Extrapolation of the Crab pulsar's giant pulses --- exemplars of coherent, high brightness temperature radiation --- to a rate of one per $10^3~$yr yields a...

Cordes, J M

2015-01-01T23:59:59.000Z

283

Reconstructing the Star Formation Histories of Galaxies  

E-Print Network [OSTI]

We present a methodological study to find out how far back and to what precision star formation histories of galaxies can be reconstructed from CMDs, from integrated spectra and Lick indices, and from integrated multi-band photometry. Our evolutionary synthesis models GALEV allow to describe the evolution of galaxies in terms of all three approaches and we have assumed typical observational uncertainties for each of them and then investigated to what extent and accuracy different star formation histories can be discriminated. For a field in the LMC bar region with both a deep CMD from HST observations and a trailing slit spectrum across exactly the same field of view we could test our modelling results against real data.

Uta Fritze; Thomas Lilly

2007-01-15T23:59:59.000Z

284

COALESCING NEUTRON STARS AS GAMMA RAY BURSTERS ?  

E-Print Network [OSTI]

We investigate the dynamics and evolution of coalescing neutron stars. The three-dimensional Newtonian equations of hydrodynamics are integrated by the `Piecewise Parabolic Method' However, we do include the effects of the emission of gravitational waves on the hydrodynamics. The properties of neutron star matter are described by the equation of state of Lattimer & Swesty. In addition to the fundamental hydrodynamic quantities, density, momentum, and energy, we follow the time evolution of the electron density in the stellar gas. Energy losses and changes of the electron abundance due to the emission of neutrinos are taken into account by an elaborate ``neutrino leakage scheme'', which employs a careful calculation of the lepton number and energy source terms of all neutrino types. The grid is Cartesian and equidistant with a resolution of 64**3 or 128**3, which allows us to calculate the self-gravity via fast Fourier transforms.

M. Ruffert; H. -Th. Janka; W. Keil; G. Schaefer

1995-03-06T23:59:59.000Z

285

Energy Star Concepts for Highway Vehicles  

SciTech Connect (OSTI)

The authors of this report, under the sponsorship of the U.S. Department of Energy (DOE) Office of Energy Efficiency and Renewable Energy (EERE) Weatherization and Intergovernmental Program, have investigated the possible application of Energy Star ratings to passenger cars and light trucks. This study establishes a framework for formulating and evaluating Energy Star rating methods that is comprised of energy- and environmental-based metrics, potential vehicle classification systems, vehicle technology factors, and vehicle selection criteria. The study tests several concepts and Energy Star rating methods using model-year 2000 vehicle data--a spreadsheet model has been developed to facilitate these analyses. This study tests two primary types of rating systems: (1) an outcome-based system that rates vehicles based on fuel economy, GHG emissions, and oil use and (2) a technology-based system that rates vehicles based on the energy-saving technologies they use. Rating methods were evaluated based on their ability to select vehicles with high fuel economy, low GHG emissions, and low oil use while preserving a full range of service (size and acceleration) and body style choice. This study concludes that an Energy Star rating for passenger cars and light trucks is feasible and that several methods could be used to achieve reasonable tradeoffs between low energy use and emissions and diversity in size, performance, and body type. It also shows that methods that consider only fuel economy, GHG emissions, or oil use will not select a diverse mix of vehicles. Finally, analyses suggest that methods that encourage the use of technology only, may result in increases in acceleration power and weight rather than reductions in oil use and GHG emissions and improvements in fuel economy.

Greene, D.L.

2003-06-24T23:59:59.000Z

286

Some simple models for quark stars  

E-Print Network [OSTI]

We find two new classes of exact solutions for the Einstein-Maxwell equations. The solutions are obtained by considering charged anisotropic matter with a linear equation of state consistent with quark stars. The field equations are integrated by specifying forms for the measure of anisotropy and a gravitational potential which are physically reasonable. The solutions found generalize the Mark-Harko model and the Komathiraj-Maharaj model. A graphical analysis indicates that the matter variables are well behaved.

S. D. Maharaj; J. M. Sunzu; S. Ray

2014-12-28T23:59:59.000Z

287

The Dark Energy Star and Stability analysis  

E-Print Network [OSTI]

We have proposed a new model of dark energy star consisting of five zones namely, solid core of constant energy density, the thin shell between core and interior, an inhomogeneous interior region with anisotropic pressures, thin shell and the exterior vacuum region. We have discussed various physical properties. The model satisfies all the physical requirements. The stability condition under small linear perturbation has also been discussed.

Piyali Bhar; Farook Rahaman

2015-01-12T23:59:59.000Z

288

Green Star Alternative Energy | Open Energy Information  

Open Energy Info (EERE)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data CenterFranconia, Virginia: Energy Resources Jump to: navigation,Ohio: EnergyGrasslands RenewableGreatwood,GreenFalls,Group LtdGreenStar

289

DayStar Technologies | Open Energy Information  

Open Energy Info (EERE)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on Office of Inspector GeneralDepartmentAUDIT REPORT Americium/CuriumSunwaysDatang Chifeng Saihanba Wind PowerDayStar

290

Eruptive Mass Loss in Very Massive Stars and Population III Stars  

E-Print Network [OSTI]

I discuss the role played by short-duration eruptive mass loss in the evolution of very massive stars. Giant eruptions of Luminous Blue Variables (LBVs) like the 19th century event of eta Carinae can remove large quantities of mass almost instantaneously, making them significant in stellar evolution. They can potentially remove much more mass from the star than line-driven winds, especially if stellar winds are highly clumped such that previous estimates of O star mass-loss rates need to be revised downward. When seen in other galaxies as ``supernova impostors'', these LBV eruptions typically last for less than a decade, and they can remove of order 10 Msun as indicated by massive nebulae around LBVs. Such extreme mass-loss rates cannot be driven by radiation pressure on spectral lines, because the lines will completely saturate during the events. Instead, these outbursts must either be continuum-driven super-Eddington winds or outright hydrodynamic explosions, both of which are insensitive to metallicity. As such, this eruptive mode of mass loss could also play a pivotal role in the evolution and ultimate fate of massive metal-poor stars in the early universe. If they occur in these Population III stars, such eruptions would also profoundly affect the chemical yield and types of remnants from early supernovae and hypernovae thought to be the origin of long gamma ray bursts.

Nathan Smith

2006-07-24T23:59:59.000Z

291

EXTENDED STAR FORMATION IN THE INTERMEDIATE-AGE LARGE MAGELLANIC CLOUD STAR CLUSTER NGC 2209  

SciTech Connect (OSTI)

We present observations of the 1 Gyr old star cluster NGC 2209 in the Large Magellanic Cloud made with the GMOS imager on the Gemini South Telescope. These observations show that the cluster exhibits a main-sequence turnoff that spans a broader range in luminosity than can be explained by a single-aged stellar population. This places NGC 2209 amongst a growing list of intermediate-age (1-3 Gyr) clusters that show evidence for extended or multiple epochs of star formation of between 50 and 460 Myr in extent. The extended main-sequence turnoff observed in NGC 2209 is a confirmation of the prediction in Keller et al. made on the basis of the cluster's large core radius. We propose that secondary star formation is a defining feature of the evolution of massive star clusters. Dissolution of lower mass clusters through evaporation results in only clusters that have experienced secondary star formation surviving for a Hubble time, thus providing a natural connection between the extended main-sequence turnoff phenomenon and the ubiquitous light-element abundance ranges seen in the ancient Galactic globular clusters.

Keller, Stefan C.; Mackey, A. Dougal; Da Costa, Gary S. [Research School of Astronomy and Astrophysics, Australian National University, Canberra (Australia)

2012-12-10T23:59:59.000Z

292

No-Hair Relations for Neutron Stars and Quark Stars: Relativistic Results  

E-Print Network [OSTI]

Astrophysical charge-free black holes are known to satisfy no-hair relations through which all multipole moments can be specified in terms of just their mass and spin angular momentum. We here investigate the possible existence of no-hair-like relations among multipole moments for neutron stars and quark stars that are independent of their equation of state. We calculate the multipole moments of these stars up to hexadecapole order by constructing uniformly-rotating and unmagnetized stellar solutions to the Einstein equations. For slowly-rotating stars, we construct stellar solutions to quartic order in spin in a slow-rotation expansion, while for rapidly-rotating stars, we solve the Einstein equations numerically with the LORENE and RNS codes. We find that the multipole moments extracted from these numerical solutions are consistent with each other. We confirm that the current-dipole is related to the mass-quadrupole in an approximately equation of state independent fashion, which does not break for rapidly ...

Yagi, Kent; Pappas, George; Yunes, Nicolas; Apostolatos, Theocharis A

2014-01-01T23:59:59.000Z

293

Radiation Pressure in Massive Star Formation  

E-Print Network [OSTI]

Stars with masses of >~ 20 solar masses have short Kelvin times that enable them to reach the main sequence while still accreting from their natal clouds. The resulting nuclear burning produces a huge luminosity and a correspondingly large radiation pressure force on dust grains in the accreting gas. This effect may limit the upper mass of stars that can form by accretion. Indeed, simulations and analytic calculations to date have been unable to resolve the mystery of how stars of 50 solar masses and up form. We present two new ideas to solve the radiation pressure problem. First, we use three-dimensional radiation hydrodynamic adaptive mesh refinement simulations to study the collapse of massive cores. We find that in three dimensions a configuration in which radiation holds up an infalling envelope is Rayleigh-Taylor unstable, leading radiation driven bubbles to collapse and accretion to continue. We also present Monte Carlo radiative transfer calculations showing that the cavities created by protostellar winds provides a valve that allow radiation to escape the accreting envelope, further reducing the ability of radiation pressure to inhibit accretion.

Mark R. Krumholz; Richard I. Klein; Christopher F. McKee

2005-10-14T23:59:59.000Z

294

Gravitational microlensing of stars with transiting planets  

E-Print Network [OSTI]

If planetary systems are ubiquitous then a fraction of stars should possess a transiting planet when being microlensed. This paper presents a study of the influence of such planets on microlensing light curves. For the giant planets recently identified, the deviations in the light curve can be substantial, although the specifics of the perturbations are dependent upon the radius of the planet relative to that of the star, the location of the planet over the stellar surface and the orientation of the sweeping caustic. Given that the instantaneous probability of transiting hot-Jupiter like planets is small, less than a percent, and only a proportion of microlensing events exhibit caustic crossing events, the probability of detecting a transiting planet during a microlensing event is small, $\\sim10^{-6}$. However, a number of factors influencing this probability, such as the number of solar type star that possess planets, are uncertain, and the prospect of detecting transiting planets in future large catalogues of microlensing light curves may be viable. The results of this study also have bearing on the gravitational microlensing of spots on the stellar surface.

Geraint F. Lewis

2001-10-17T23:59:59.000Z

295

Habitable planets around the star Gl 581?  

E-Print Network [OSTI]

Radial velocity surveys are now able to detect terrestrial planets at habitable distance from M-type stars. Recently, two planets with minimum masses below 10 Earth masses were reported in a triple system around the M-type star Gliese 581. Using results from atmospheric models and constraints from the evolution of Venus and Mars, we assess the habitability of planets Gl 581c and Gl 581d and we discuss the uncertainties affecting the habitable zone (HZ) boundaries determination. We provide simplified formulae to estimate the HZ limits that may be used to evaluate the astrobiological potential of terrestrial exoplanets that will hopefully be discovered in the near future. Planets Gl 581c and 'd' are near, but outside, what can be considered as the conservative HZ. Planet 'c' receives 30% more energy from its star than Venus from the Sun, with an increased radiative forcing caused by the spectral energy distribution of Gl 581. Its habitability cannot however be positively ruled out by theoretical models due to uncertainties affecting cloud properties. Irradiation conditions of planet 'd' are comparable with those of early Mars. Thanks to the warming effect of CO2-ice clouds planet 'd' might be a better candidate for the first exoplanet known to be potentially habitable. A mixture of various greenhouse gases could also maintain habitable conditions on this planet.

Franck Selsis; J. F. Kasting; B. Levrard; J. Paillet; I. Ribas; X. Delfosse

2007-11-21T23:59:59.000Z

296

Habitable planets around the star Gl 581?  

E-Print Network [OSTI]

Radial velocity surveys are now able to detect terrestrial planets at habitable distance from M-type stars. Recently, two planets with minimum masses below 10 Earth masses were reported in a triple system around the M-type star Gliese 581. Using results from atmospheric models and constraints from the evolution of Venus and Mars, we assess the habitability of planets Gl 581c and Gl 581d and we discuss the uncertainties affecting the habitable zone (HZ) boundaries determination. We provide simplified formulae to estimate the HZ limits that may be used to evaluate the astrobiological potential of terrestrial exoplanets that will hopefully be discovered in the near future. Planets Gl 581c and 'd' are near, but outside, what can be considered as the conservative HZ. Planet 'c' receives 30% more energy from its star than Venus from the Sun, with an increased radiative forcing caused by the spectral energy distribution of Gl 581. Its habitability cannot however be positively ruled out by theoretical models due to u...

Selsis, Franck; Levrard, B; Paillet, J; Ribas, I; Delfosse, X

2007-01-01T23:59:59.000Z

297

Gravitational waves from rapidly rotating neutron stars  

E-Print Network [OSTI]

Rapidly rotating neutron stars in Low Mass X-ray Binaries have been proposed as an interesting source of gravitational waves. In this chapter we present estimates of the gravitational wave emission for various scenarios, given the (electromagnetically) observed characteristics of these systems. First of all we focus on the r-mode instability and show that a 'minimal' neutron star model (which does not incorporate exotica in the core, dynamically important magnetic fields or superfluid degrees of freedom), is not consistent with observations. We then present estimates of both thermally induced and magnetically sustained mountains in the crust. In general magnetic mountains are likely to be detectable only if the buried magnetic field of the star is of the order of $B\\approx 10^{12}$ G. In the thermal mountain case we find that gravitational wave emission from persistent systems may be detected by ground based interferometers. Finally we re-asses the idea that gravitational wave emission may be balancing the accretion torque in these systems, and show that in most cases the disc/magnetosphere interaction can account for the observed spin periods.

Brynmor Haskell; Nils Andersson; Caroline D`Angelo; Nathalie Degenaar; Kostas Glampedakis; Wynn C. G. Ho; Paul D. Lasky; Andrew Melatos; Manuel Oppenoorth; Alessandro Patruno; Maxim Priymak

2014-07-31T23:59:59.000Z

298

Neutron Star Superfluidity, Dynamics and Precession  

E-Print Network [OSTI]

Basic rotational and magnetic properties of neutron superfluids and proton superconductors in neutron stars are reviewed. The modes of precession of the neutron superfluid are discussed in detail. We emphasize that at finite temperature, pinning of superfluid vortices does not offer any constraint on the precession. Any pinning energies can be surmounted by thermal activation and there exists a dynamical steady state in which the superfluid follows the precession of the crust at a small lag angle between the crust and superfluid rotation velocity vectors. At this small lag the system is far from the critical conditions for unpinning, even if the observed precession of the crust may entail a large angle between the figure axis and the crust's rotation velocity vector. We conclude that if long period modulations of pulse arrival times and pulse shapes observed in a pulsar like the PSR B1828-11 are due to the precession of the neutron star, this does not have any binding implications about the existence of pinning by flux lines or the existence of Type II superconductivity in the neutron star.

M. Ali Alpar

2005-05-04T23:59:59.000Z

299

Star Formation Histories in the Local Group  

E-Print Network [OSTI]

Deep color magnitude diagrams extending to the main sequence provide the most direct measure of the detailed star formation history in a stellar population. With large investments of observing time, HST can obtain such data for populations out to 1 Mpc, but its field of view is extremely small in comparison to the size of Local Group galaxies. This limitation severely constrains our understanding of galaxy formation. For example, the largest galaxy in the Local Group, Andromeda, offers an ideal laboratory for studying the formation of large spiral galaxies, but the galaxy shows substructure on a variety of scales, presumably due to its violent merger history. Within its remaining lifetime, HST can only sample a few sight-lines through this complex galaxy. In contrast, a wide field imager could provide a map of Andromeda's halo, outer disk, and tidal streams, revealing the spatially-dependent star formation history in each structure. The same data would enable many secondary studies, such as the age variation in Andromeda's globular cluster system, gigantic samples of variable stars, and microlensing tracers of the galaxy's dark matter distribution.

Thomas M. Brown

2004-07-09T23:59:59.000Z

300

Statistical theory of thermal evolution of neutron stars  

E-Print Network [OSTI]

Thermal evolution of neutron stars is known to depend on the properties of superdense matter in neutron star cores. We suggest a statistical analysis of isolated cooling middle-aged neutron stars and old transiently accreting quasi-stationary neutron stars warmed up by deep crustal heating in low-mass X-ray binaries. The method is based on simulations of the evolution of stars of different masses and on averaging the results over respective mass distributions. This gives theoretical distributions of isolated neutron stars in the surface temperature--age plane and of accreting stars in the photon thermal luminosity--mean mass accretion rate plane to be compared with observations. This approach permits to explore not only superdense matter but also the mass distributions of isolated and accreting neutron stars. We show that the observations of these stars can be reasonably well explained by assuming the presence of the powerful direct Urca process of neutrino emission in the inner cores of massive stars, introd...

Beznogov, M V

2014-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "waha lone star" 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

Explosive Combustion of a Neutron Star into a Quark Star: the non-premixed scenario  

E-Print Network [OSTI]

We review aspects of the hydrodynamical combustion of nuclear matter to strange quark matter in a neutron star. Numerical studies on non-premixed combustion that consistently include hydrodynamical flows in a reactive-diffusive setup show that in 1D, the conversion (burning) front moves at sub-sonic speeds and stops short of converting the entire star to SQM, essentially due to advective forces. However, in the process, we also find that neutrino cooling of the interface causes it to wrinkle, laying a platform for a deflagrative-to-detonative transition (DDT). We outline progress on improvements in the burning code (Burn-UD: http://quarknova.ucalgary.ca/software/Burn-UD/) that will ultimately reveal the mechanism that can explode the outermost layers of even a dense compact object like a neutron star.

Ouyed, Rachid; Jaikumar, Prashanth

2013-01-01T23:59:59.000Z

302

Rotational and magnetic field instabilities in neutron stars  

SciTech Connect (OSTI)

In this short review we present recent results on the dynamics of neutron stars and their magnetic fields. We discuss the progress that has been made, during the last 5 years, in understanding the rotational instabilities with emphasis to the one due to the f-mode, the possibility of using gravitational wave detection in constraining the parameters of neutron stars and revealing the equation of state as well as the detectability of gravitational waves produced during the unstable phase of a neutron star’s life. In addition we discuss the dynamics of extremely strong magnetic fields observed in a class of neutron stars (magnetars). Magnetic fields of that strength are responsible for highly energetic phenomena (giant flares) and we demonstrate that the analysis of the emitted electromagnetic radiation can lead in constraining the parameters of neutron stars. Furthermore, we present our results from the study of such violent phenomena in association with the emission of gravitational radiation.

Kokkotas, Kostas D. [Theoretical Astrophysics, IAAT, Eberhard Karls University of Tübingen, Tübingen 72076 (Germany)

2014-01-14T23:59:59.000Z

303

X-ray aurora in neutron star magnetospheres  

E-Print Network [OSTI]

In this study we propose a new generic model for QPOs based on oscillation modes of neutron star magnetospheres. We argue that the interaction of the accretion disk with the magnetosphere can excite resonant shear Alfven waves in a region of enhanced density gradients. We demonstrate that depending on the distance of this enhanced density region from the star and the magnetic field strength, the frequency of the field line resonance can range from several Hz (weaker field, farther from star), to approximately kHz frequencies (stronger field, ~ 2-10 star radii from the star). We show that such oscillations are able to significantly modulate inflow of matter from the high density region toward the star surface, and possibly produce the observed X-ray spectrum. In addition, we show that the observed 2:3 frequency ratio of QPOs is a natural result of our model.

Vahid Rezania; John C. Samson; Peter Dobias

2004-03-27T23:59:59.000Z

304

The Cosmic Near Infrared Background: Remnant Light from Early Stars  

E-Print Network [OSTI]

The redshifted ultraviolet light from early stars at z ~ 10 contributes to the cosmic near infrared background. We present detailed calculations of its spectrum with various assumptions about metallicity and mass spectrum of early stars. We show that if the near infrared background has a stellar origin, metal-free stars are not the only explanation of the excess near infrared background; stars with metals (e.g. Z=1/50 Z_sun) can produce the same amount of background intensity as the metal-free stars. We quantitatively show that the predicted average intensity at 1-2 microns is essentially determined by the efficiency of nuclear burning in stars, which is not very sensitive to metallicity. We predict \

Elizabeth Fernandez; Eiichiro Komatsu

2005-08-08T23:59:59.000Z

305

The helium abundances in HgMn and normal stars  

E-Print Network [OSTI]

The parameter-free model of diffusion in the atmospheres of HgMn stars (Michaud 1986; Michaud et al 1979) predicts that helium should sink below the He II ionization zone in order that diffusion of other elements may take place, and that all HgMn stars should have deficits of helium in their photospheres, with a minimum deficit of 0.3 dex. In this study, the Smith & Dworetsky (1993) sample of HgMn stars and normal comparison stars is examined, and the helium abundances determined by spectrum synthesis using echelle spectra taken at Lick Observatory and the AAT. The prediction is confirmed; all HgMn stars are deficient in He by as much as 1.5 dex. Also, two HgMn stars, HR7361 and HR7664, show clear evidence of helium stratification.

M. M. Dworetsky

2004-07-26T23:59:59.000Z

306

Continuous-time quantum walks on star graphs  

SciTech Connect (OSTI)

In this paper, we investigate continuous-time quantum walk on star graphs. It is shown that quantum central limit theorem for a continuous-time quantum walk on star graphs for N-fold star power graph, which are invariant under the quantum component of adjacency matrix, converges to continuous-time quantum walk on K{sub 2} graphs (complete graph with two vertices) and the probability of observing walk tends to the uniform distribution.

Salimi, S. [Department of Physics, University of Kurdistan, P.O. Box 66177-15175, Sanandaj (Iran, Islamic Republic of)], E-mail: shsalimi@uok.ac.ir

2009-06-15T23:59:59.000Z

307

THE SUN AS AN XRAY STAR: OVERVIEW OF THE METHOD  

E-Print Network [OSTI]

THE SUN AS AN X­RAY STAR: OVERVIEW OF THE METHOD G. PERES, S. ORLANDO AND F. REALE Istituto ed.e., the close similarity of the physical phenomena occurring on the Sun and on late­type active stars, by taking­ray instruments aimed at stars other than the Sun. Here we illustrate the application of this method to ROSAT

308

Negative feedback effects on star formation history and cosmic reionization  

E-Print Network [OSTI]

After considering the effects of negative feedback on the process of star formation, we explore the relationship between star formation process and the associated feedback, by investigating how the mechanical feedback from supernovae(SNe) and radiative feedback from luminous objects regulate the star formation rate and therefore affect the cosmic reionization.Based on our present knowledge of the negative feedback theory and some numerical simulations, we construct an analytic model in the framework of the Lambda cold dark matter model. In certain parameter regions, our model can explain some observational results properly. In large halos(T_vir>10000 K), both mechanical and radiative feedback have a similar behavior: the relative strength of negative feedback reduces as the redshift decreases. In contrast, in small halos (T_virfeedback gets stronger when the redshift decreases. And the star formation rate in these small halos depends very weakly on the star-formation efficiency. Our results show that the radiative feedback is important for the early generation stars. It can suppress the star formation rate considerably. But the mechanical feedback from the SNe explosions is not able to affect the early star formation significantly. The early star formation in small-halo objects is likely to be self-regulated. The radiative and mechanical feedback dominates the star formation rate of the PopII/I stars all along. The feedback from first generation stars is very strong and should not be neglected. However, their effects on the cosmic reionization are not significant, which results in a small contribution to the optical depth of Thomson scattering.

Lei Wang; Jirong Mao; Shouping Xiang; Ye-Fei Yuan

2008-12-22T23:59:59.000Z

309

A search for rapid pulsations among 9 luminous Ap stars  

E-Print Network [OSTI]

The rapidly oscillating Ap stars are of importance for studying the atmospheric structure of stars where the process of chemical element diffusion is significant. We have performed a survey for rapid oscillations in a sample of 9 luminous Ap stars, selected from their location in the colour-magnitude diagram as more evolved main-sequence Ap stars that are inside the instability strip for rapidly oscillating Ap (roAp) stars. Until recently this region was devoid of stars with observed rapid pulsations. We used the VLT UV-Visual Echelle Spectrograph (UVES) to obtain high time resolution spectroscopy to make the first systematic spectroscopic search for rapid oscillations in this region of the roAp instability strip. We report 9 null-detections with upper limits for radial-velocity amplitudes of 20 - 65 m/s and precisions of 7 - 20 m/s for combinations of Nd and Pr lines. Cross-correlations confirm these null-results. At least six stars are magnetic and we provide magnetic field measurements for four of them, of which three are newly discovered magnetic stars. It is found that four stars have magnetic fields smaller than ~ 2 kG, which according to theoretical predictions might be insufficient for suppressing envelope convection around the magnetic poles for more evolved Ap stars. Suppression of convection is expected to be essential for the opacity mechanism acting in the hydrogen ionisation zone to drive the high-overtone roAp pulsations efficiently. Our null-results suggest that the more evolved roAp stars may require particularly strong magnetic fields to pulsate. Three of the studied stars do, however, have magnetic fields stronger than 5 kG.

L. M. Freyhammer; D. W. Kurtz; M. S. Cunha; G. Mathys; V. G. Elkin; J. D. Riley

2008-01-03T23:59:59.000Z

310

Stability of thin-shell interfaces inside compact stars  

E-Print Network [OSTI]

We use the thin-shell Darmois-Israel formalism to model and assess the stability of the interfaces separating phases, e.g. the core and the crust, within compact stars. We exemplify the relevance and non-triviality of this treatment in the simplest case of an incompressible star, in constant pressure phase transitions, and in the case of strange quark stars with crust.

Jonas P. Pereira; Jaziel G. Coelho; Jorge A. Rueda

2015-01-05T23:59:59.000Z

311

On the ultimate fate of AM Her stars  

E-Print Network [OSTI]

We suggest, that the magnetic field of the white dwarf in AM Her systems loses coupling to the secondary star when the latter becomes non-magnetic at the transition from a late main sequence star to a cool degenerate brown dwarf. This leads to spin-up of the primary white dwarf. After synchronous rotation is lost the systems do not appear as AM Her stars anymore. We discuss the further evolution of such systems.

F. Meyer; E. Meyer-Hofmeister

1999-05-06T23:59:59.000Z

312

Neutron stars in f(R) gravity with perturbative constraints  

SciTech Connect (OSTI)

We study the structure of neutron stars in f(R) gravity theories with perturbative constraints. We derive the modified Tolman-Oppenheimer-Volkov equations and solve them for a polytropic equation of state. We investigate the resulting modifications to the masses and radii of neutron stars and show that observations of surface phenomena alone cannot break the degeneracy between altering the theory of gravity versus choosing a different equation of state of neutron-star matter. On the other hand, observations of neutron-star cooling, which depends on the density of matter at the stellar interior, can place significant constraints on the parameters of the theory.

Cooney, Alan; DeDeo, Simon; Psaltis, Dimitrios [Department of Physics, University of Arizona, Tucson, Arizona 85721 (United States); Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, New Mexico 87501 (United States); Departments of Astronomy and Physics, University of Arizona, Tucson, Arizona 85721 (United States)

2010-09-15T23:59:59.000Z

313

Calendar Year 2007 Program Benefits for ENERGY STAR Labeled Products  

E-Print Network [OSTI]

increasing market penetration of ENERGY STAR HVAC and anyHVAC is expressed in million square feet 7) Roofing is expressed in billion square feet 8) PC market

Sanchez, Marla Christine

2008-01-01T23:59:59.000Z

314

Calendar Year 2008 Program Benefits for ENERGY STAR Labeled Products  

E-Print Network [OSTI]

increasing market penetration of ENERGY STAR HVAC and anyHVAC is expressed in million square feet 7) Roofing is expressed in billion square feet 8) PC market

Homan, GregoryK

2010-01-01T23:59:59.000Z

315

Delmarva Power- Home Performance with Energy Star Incentive Program  

Broader source: Energy.gov [DOE]

Delmarva Power and Light Company offers the Home Performance with Energy Star Program, which provides incentives for residential customers who have audits performed by participating contractors....

316

PEPCO- Home Performance with Energy Star Incentive Program  

Broader source: Energy.gov [DOE]

The Potomac Electric Power Company (PEPCO) offers the Home Performance with Energy Star Program which provides incentives for residential customers who have audits performed by participating...

317

astrophysics connecting stars: Topics by E-print Network  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

the structure and evolution of single and multiple stars, compact objects, SNe, gamma-ray bursts, solar neutrinos, and extreme physics on stellar scales. Central to the progress...

318

Carbon and Strontium Abundances of Metal-Poor Stars  

E-Print Network [OSTI]

We present carbon and strontium abundances for 100 metal-poor stars measured from R$\\sim $7000 spectra obtained with the Echellette Spectrograph and Imager at the Keck Observatory. Using spectral synthesis of the G-band region, we have derived carbon abundances for stars ranging from [Fe/H]$=-1.3$ to [Fe/H]$=-3.8$. The formal errors are $\\sim 0.2$ dex in [C/Fe]. The strontium abundance in these stars was measured using spectral synthesis of the resonance line at 4215 {\\AA}. Using these two abundance measurments along with the barium abundances from our previous study of these stars, we show it is possible to identify neutron-capture-rich stars with our spectra. We find, as in other studies, a large scatter in [C/Fe] below [Fe/H]$ = -2$. Of the stars with [Fe/H]$<-2$, 9$\\pm$4% can be classified as carbon-rich metal-poor stars. The Sr and Ba abundances show that three of the carbon-rich stars are neutron-capture-rich, while two have normal Ba and Sr. This fraction of carbon enhanced stars is consistent with other studies that include this metallicity range.

David K. Lai; Jennifer A. Johnson; Michael Bolte; Sara Lucatello

2007-06-20T23:59:59.000Z

319

Coordinate Data and Stars Identification in Astrophysical Catalogs  

E-Print Network [OSTI]

The aim of our paper is to make high-precision positional stellar catalogs by compiling large astrophysical data bulk and large astrometrical surveys. The data reliability and uniqueness is the primary request. The common precision of 1 arc sec in coordinates is insufficient now to guarantee the simple identification of stars. Therefore the technique of catalogs verification become relevant. The paper presents the outcome of stars identification in The Henry Draper Extension Charts catalog and Variable stars catalog using proper method. Examples of conflicts permission concerning doubles and multiples stars in astrophysical catalogs are discussed.

Ashimbaeva, Nuriya T

2008-01-01T23:59:59.000Z

320

Coordinate Data and Stars Identification in Astrophysical Catalogs  

E-Print Network [OSTI]

The aim of our paper is to make high-precision positional stellar catalogs by compiling large astrophysical data bulk and large astrometrical surveys. The data reliability and uniqueness is the primary request. The common precision of 1 arc sec in coordinates is insufficient now to guarantee the simple identification of stars. Therefore the technique of catalogs verification become relevant. The paper presents the outcome of stars identification in The Henry Draper Extension Charts catalog and Variable stars catalog using proper method. Examples of conflicts permission concerning doubles and multiples stars in astrophysical catalogs are discussed.

Nuriya T. Ashimbaeva

2008-10-01T23:59:59.000Z

Note: This page contains sample records for the topic "waha lone star" 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

Magic Valley Electric Cooperative- ENERGY STAR Builders Program (Texas)  

Broader source: Energy.gov [DOE]

Magic Valley Electric Cooperative's (MVEC) ENERGY STAR Builders Program offers a variety of incentives to builders of energy efficiency homes within MVEC service territory. Incentives are provided...

322

A Random Walk through Star and Planet Formation  

E-Print Network [OSTI]

and its Neptune-Mass Planet 3.1 Introduction . . . . . . .of Low Mass Star Formation . . . . . 1.3 Planet FormationConstraining Theories of Planet Formation and Evolution .

Maness, Holly

2010-01-01T23:59:59.000Z

323

The winds of the hot massive first stars  

E-Print Network [OSTI]

We study dynamical aspects of circumstellar environment around massive zero-metallicity first stars. For this purpose we apply our NLTE wind models. We show that the hydrogen-helium stellar wind from stationary massive first generation (Population III) stars (driven either by the line (bound-bound) or continuum (bound-free and free-free) transitions) is unlikely. The possibility of expulsion of chemically homogeneous wind and the role of minor isotopes are also discussed. Finally, we estimate the importance of hydrogen and helium lines for shutting off the initial accretion onto first stars and its influence on initial mass function of first stars.

J. Krticka; J. Kubat

2005-09-07T23:59:59.000Z

324

The Massive Star Population of Cygnus OB2  

E-Print Network [OSTI]

We have compiled a significantly updated and comprehensive census of massive stars in the nearby Cygnus OB2 association by gathering and homogenising data from across the literature. The census contains 169 primary OB stars, including 52 O-type stars and 3 Wolf-Rayet stars. Spectral types and photometry are used to place the stars in a Hertzprung-Russell diagram, which is compared to both non-rotating and rotating stellar evolution models, from which stellar masses and ages are calculated. The star formation history and mass function of the association are assessed, and both are found to be heavily influenced by the evolution of the most massive stars to their end states. We find that the mass function of the most massive stars is consistent with a `universal' power-law slope of Gamma = 1.3. The age distribution inferred from stellar evolutionary models with rotation and the mass function suggest the majority of star formation occurred more or less continuously between 1 and 7 Myr ago, in agreement with studi...

Wright, Nicholas J; Mohr-Smith, Michael

2015-01-01T23:59:59.000Z

325

Calendar Year 2009 Program Benefits for ENERGY STAR Labeled Products  

E-Print Network [OSTI]

Administration, Office of Energy Markets and End Use.Administration, Office of Energy Markets and End Use.ICF Consulting. 2003. Energy Star Market Penetration Report

Homan, Gregory K

2011-01-01T23:59:59.000Z

326

Calendar Year 2008 Program Benefits for ENERGY STAR Labeled Products  

E-Print Network [OSTI]

Administration, Office of Energy Markets and End Use.Administration, Office of Energy Markets and End Use.Protection Agency: ENERGY STAR Market Share of computers,

Homan, GregoryK

2010-01-01T23:59:59.000Z

327

accreting compact stars: Topics by E-print Network  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

of the millisecond brightness oscillations from low mass X-ray binaries during thermonuclear bursts can provide us with important information about compact star parameters....

328

NEW YOUNG STAR CANDIDATES IN CG4 AND Sa101  

SciTech Connect (OSTI)

The CG4 and Sa101 regions together cover a region of {approx}0.5 deg{sup 2} in the vicinity of a 'cometary globule' that is part of the Gum Nebula. There are seven previously identified young stars in this region; we have searched for new young stars using mid- and far-infrared data (3.6-70 {mu}m) from the Spitzer Space Telescope, combined with ground-based optical data and near-infrared data from the Two Micron All Sky Survey. We find infrared excesses in all six of the previously identified young stars in our maps and identify 16 more candidate young stars based on apparent infrared excesses. Most (73%) of the new young stars are Class II objects. There is a tighter grouping of young stars and young star candidates in the Sa101 region, in contrast to the CG4 region, where there are fewer young stars and young star candidates, and they are more dispersed. Few likely young objects are found in the 'fingers' of the dust being disturbed by the ionization front from the heart of the Gum Nebula.

Rebull, L. M.; Laine, S.; Laher, R.; Legassie, M. [Spitzer Science Center/Caltech, M/S 220-6, 1200 E. California Blvd., Pasadena, CA 91125 (United States); Johnson, C. H. [Breck School Science Department, 123 Ottawa Ave., N., Golden Valley, MN 55422 (United States); Hoette, V. [The University of Chicago Department of Astronomy and Astrophysics, Yerkes Observatory Education and Outreach, 373 W. Geneva St., Williams Bay, WI 53191 (United States); Kim, J. S.; Foster, M. [Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721 (United States); Mallory, C. R. [Department of Astronomy, Pierce College, 6201 Winnetka Ave., Woodland Hills, CA 91371 (United States); McCarron, K. [Science Division, Oak Park and River Forest High School, 201 N. Scoville Ave., Oak Park, IL 60302 (United States); Sherry, W. H., E-mail: luisa.rebull@jpl.nasa.gov [NOAO/NSO, 950 N. Cherry Ave., Tucson, AZ 85719 (United States)

2011-07-15T23:59:59.000Z

329

The Federal Guiding Principles Checklist in ENERGY STAR Portfolio  

Broader source: Energy.gov [DOE]

This webcast will teach Federal energy and sustainability professionals how to use the ENERGY STAR measurement and tracking tool, Portfolio Manager, to help ensure compliance with the Guiding...

330

STAR Images: Image gallery from the Solenoidal Tracker at RHIC  

DOE Data Explorer [Office of Scientific and Technical Information (OSTI)]

The primary physics task of STAR is to study the formation and characteristics of the quark-gluon plasma (QGP), a state of matter believed to exist at sufficiently high energy densities. STAR consists of several types of detectors, each specializing in detecting certain types of particles or characterizing their motion. These detectors allow final statements to be made about the collision. The gallery of STAR images makes available a small collection of event-generated images from Gold-Beam experiments, a simulation of TCP Drift, and a library of STAR instrument and construction photos. [See also DDE00093

331

EPA ENERGY STAR Webcast: Benchmarking Water/Wastewater Treatment...  

Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

Benchmarking WaterWastewater Treatment Facilities in Portfolio Manager EPA ENERGY STAR Webcast: Benchmarking WaterWastewater Treatment Facilities in Portfolio Manager November...

332

Feedback Processes [in Massive Star Formation]: A Theoretical Perspective  

E-Print Network [OSTI]

I review the evidence for the importance of feedback from massive stars at small and large scales. The feedback mechanisms include accretion luminosity, ionizing radiation, collimated outflows, and stellar winds. The good news is that feedback doesn't entirely prevent the formation of massive stars, while the bad news is that we don't know what does limit their masses. Feedback from massive stars also influences their surroundings. I argue that this does not produce a triggering efficiency above unity, nor does it prevent lots of prompt star formation in GMCs, though it may preserve massive remnants of the clouds for many dynamical times.

Mordecai-Mark Mac Low

2007-11-26T23:59:59.000Z

333

Department of Energy Honors 50 ENERGY STAR® Partners that Saved...  

Energy Savers [EERE]

security." ENERGY STAR began in 1992 as a voluntary, market-based partnership to reduce air pollution through increased energy efficiency. Today, DOE, in partnership with EPA,...

334

EPA ENERGY STAR Webcast - Successes in Sustainability: Tenants...  

Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

Successes in Sustainability: Tenants and Landlords Team Up on Energy EPA ENERGY STAR Webcast - Successes in Sustainability: Tenants and Landlords Team Up on Energy November 12,...

335

Home Performance with ENERGY STAR - Webinar Slides | Department...  

Energy Savers [EERE]

with ENERGY STAR - 2014 BTO Peer Review Better Buildings Neighborhood Program Home Accomplishments History Better Buildings Partners Stories Interviews Videos Contact Us...

336

Caby Photometry of the Hyades Comparisons to the Field Stars  

E-Print Network [OSTI]

Intermediate-band photometry of the Hyades cluster on the Caby system is presented for dwarf stars ranging from spectral type A through late K. A mean hk, b-y relation is constructed using only single stars without anomalous atmospheres and compared to the field stars of the solar neighborhood. For the F dwarfs, the Hyades relation defines an approximate LOWER bound in the two-color diagram, consistent with an [Fe/H] between +0.10 and +0.15. These index-color diagrams follow the common convention of presenting stars with highest abundance at the bottom of the plot although the index values for the metal-rich stars are numerically larger. For field F dwarfs in the range [Fe/H] between +0.4 and -1.0, [Fe/H] = -5.6 delta-hk + 0.125, with no evidence for a color dependence in the slope. For the G and K dwarfs, the Hyades mean relation crosses the field star distribution in the two-color diagram, defining an approximate UPPER bound for the local disk stars. Stars found above the Hyades stars fall in at least one o...

Anthony-Twarog, B J; Yu, J

2002-01-01T23:59:59.000Z

337

PROPERTIES OF OSCILLATION MODES IN SUBGIANT STARS OBSERVED BY KEPLER  

SciTech Connect (OSTI)

Mixed modes seen in evolved stars carry information on their deeper layers that can place stringent constraints on their physics and on their global properties (mass, age, etc.). In this study, we present a method to identify and measure all oscillatory mode characteristics (frequency, height, width). Analyzing four subgiant stars, we present the first measure of the effect of the degree of mixture on the l = 1 mixed mode characteristics. We also show that some stars have measurable l = 2 mixed modes and discuss the interest of their measure to constrain the deeper layers of stars.

Benomar, O.; Bedding, T. R.; Stello, D.; White, T. R.; Kuehn, C. A. [Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney, Sydney, NSW 2006 (Australia); Mosser, B.; Belkacem, K. [LESIA, Observatoire de Paris, CNRS UMR 8109, Universite Paris Diderot, 5 Place J. Janssen, F-92195 Meudon (France); Garcia, R. A. [Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot (France); IRFU/SAp, Centre de Saclay, F-91191 Gif-sur-Yvette Cedex (France); Deheuvels, S. [Institut de Recherche en Astrophysique et Planetologie, Universite de Toulouse, UPS-OMP, CNRS, 14 Avenue Edouard Belin, F-31400 Toulouse (France); Christensen-Dalsgaard, J. [Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C (Denmark)

2013-04-20T23:59:59.000Z

338

The Metallicity Distribution of Intracluster Stars in Virgo  

E-Print Network [OSTI]

We have used the Hubble Space Telescope's Advanced Camera for Surveys (ACS) to detect and measure ~5300 stars in a single intracluster field in the Virgo Cluster. By performing F606W and F814W photometry on these stars, we have determined their metallicity distribution function, and constrained the types of stars present in this portion of Virgo's intracluster space. Based on the small number of stars detected brighter than the red giant branch (RGB) tip, we suggest that in this region, Virgo's intracluster stars are mostly old (>~10 Gyr). Through analysis of the RGB stars themselves, we determine that the population contains the full range of metallicities probed (-2.3-0.5. The spatial distribution of the most metal-poor stars in the field shows significantly more structure than that of the metal-rich stars, indicating that the intracluster population is not well-mixed. We discuss the implications these observations have for the production of intracluster stars and the dynamical evolution of the Virgo Cluster.

Benjamin F. Williams; Robin Ciardullo; Patrick R. Durrell; Matt Vinciguerra; John J. Feldmeier; George H. Jacoby; Steinn Sigurdsson; Ted von Hippel; Henry C. Ferguson; Nial R. Tanvir; Magda Arnaboldi; Ortwin Gerhard; J. Alfonso L. Aguerri; Ken Freeman

2006-10-12T23:59:59.000Z

339

Compact Stars in low-mass X-ray binaries  

E-Print Network [OSTI]

We propose a model for compact stars in low-mass X-ray binaries(LMXBs) namely KS 1731-260, EXO 1745-248 and 4U 1608-52. Here we investigate the physical phenomena of a compact star in the LMXBs. Using our model, we have calculated central density, surface density, mass(M) and red-shift for the above mentioned compact stars, which is very much consistent with the reported data. We also obtain the possible equation of state(EOS) of the stars which is physically acceptable.

Sk. Monowar Hossein; Sajahan Molla; Md. Abdul Kayum Jafry; Mehedi Kalam

2014-08-13T23:59:59.000Z

340

Stars and gas in the Medusa merger  

E-Print Network [OSTI]

The Medusa (NGC 4194) is a well-studied nearby galaxy with the disturbed appearance of a merger and evidence for ongoing star formation. In order to test whether it could be the result of an interaction between a gas-rich disk-like galaxy and a larger elliptical, we have carried out optical and radio observations of the stars and the gas in the Medusa, and performed $N$-body numerical simulations of the evolution of such a system. We used the Nordic Optical Telescope to obtain a deep V-band image and the Westerbork Radio Synthesis Telescope to map the large-scale distribution and kinematics of atomic hydrogen. A single HI tail was found to the South of the Medusa with a projected length of 56 kpc (5') and a gas mass of 7* 10^8 M_sun, thus harbouring about one third of the total HI mass of the system. HI was also detected in absorption toward the continuum in the center. HI was detected in a small nearby galaxy to the North-West of the Medusa at a projected distance of 91 kpc. It is, however, unlikely that this galaxy has had a significant influence on the evolution of the Medusa. The simulations of the slightly prograde infall of a gas-rich disk galaxy on an larger, four time more massive elliptical (spherical) galaxy reproduce most of the observed features of the Medusa.Thus, the Medusa is an ideal object to study the merger-induced star formation contribution from the small galaxy of a minor merger.

E. Manthey; S. Huettemeister; S. Aalto; C. Horellou; P. Bjerkeli

2008-08-28T23:59:59.000Z

Note: This page contains sample records for the topic "waha lone star" 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.


341

A Heavy Flavor Tracker for STAR  

SciTech Connect (OSTI)

The STAR Collaboration proposes to construct a state-of-the-art microvertex detector,the Heavy Flavor Tracker (HFT), utilizing active pixel sensors and silicon strip technology. The HFT will significantly extend the physics reach of the STAR experiment for precision measurement of the yields and spectra of particles containing heavy quarks. This will be accomplished through topological identification of D mesons by reconstruction of their displaced decay vertices with a precision of approximately 50 mu m in p+p, d+A, and A+A collisions. The HFT consists of 4 layers of silicon detectors grouped into two sub-systems with different technologies, guaranteeing increasing resolution when tracking from the TPC and the Silicon Strip Detector (SSD) towards the vertex of the collision. The Intermediate Silicon Tracker (IST), consisting of two layers of single-sided strips, is located inside the SSD. Two layers of Silicon Pixel Detector (PIXEL) are inside the IST. The PIXEL detectors have the resolution necessary for a precision measurement of the displaced vertex. The PIXEL detector will use CMOS Active Pixel Sensors (APS), an innovative technology never used before in a collider experiment. The APSsensors are only 50 mu m thick and at a distance of only 2.5 cm from the interaction point. This opens up a new realm of possibilities for physics measurements. In particular, a thin detector (0.28percent radiation length per layer) in STAR makes it possible to do the direct topological reconstruction of open charm hadrons down to very low pT by the identification of the charged daughters of the hadronic decay.

Chasman, C.; Beavis, D.; Debbe, R.; Lee, J.H.; Levine, M.J.; Videbaek, F.; Xu, Z.; Kleinfelder, S.; Li, S.; Cendejas, R.; Huang, H.; Sakai, S.; Whitten, C.; Joseph, J.; Keane, D.; Margetis, S.; Rykov, V.; Zhang, W.M.; Bystersky, M.; Kapitan, J.; Kushpil, V.; Sumbera, M.; Baudot, J.; Hu-Guo, C.; Shabetai, A.; Szelezniak, M.; Winter, M.; Kelsey, J.; Milner, R.; Plesko, M.; Redwine, R.; Simon, F.; Surrow, B.; Van Nieuwenhuizen, G.; Anderssen, E.; Dong, X.; Greiner, L.; Matis, H.S.; Morgan, S.; Ritter, H.G.; Rose, A.; Sichtermann, E.; Singh, R.P.; Stezelberger, T.; Sun, X.; Thomas, J.H.; Tram, V.; Vu, C.; Wieman, H.H.; Xu, N.; Hirsch, A.; Srivastava, B.; Wang, F.; Xie, W.; Bichsel, H.

2008-02-25T23:59:59.000Z

342

Helium enhancements in globular cluster stars from Asymptotic Giant Branch star pollution  

E-Print Network [OSTI]

Using a chemical evolution model we investigate the intriguing suggestion that there are populations of stars in some globular clusters (e.g. NGC 2808, omega Centauri) with enhanced levels of helium (Y from about 0.28 to 0.40) compared to the majority of the population that presumably have a primordial helium abundance. We assume that a previous generation of massive low-metallicity Asymptotic Giant Branch (AGB) stars has polluted the cluster gas via a slow stellar wind. We use two independent sets of AGB yields computed from detailed models to follow the evolution of helium, carbon, nitrogen and oxygen in the cluster gas using a Salpeter initial mass function (IMF) and a number of top-heavy IMFs. In no case were we able to fit the observational constraints, Y > 0.30 and C+N+O approximately constant. Depending on the shape of the IMF and the yields, we either obtained Y approximately greater than 0.30 and large increases in C+N+O or Y < 0.30 and C+N+O approximately constant. These results suggest that either AGB stars alone are not responsible for the large helium enrichment or that any dredge-up from this generation of stars was less than predicted by standard models.

Amanda Karakas; Yeshe Fenner; Alison Sills; Simon Campbell; John Lattanzio

2006-05-21T23:59:59.000Z

343

Energy Star Appliances 1 Texas A&M AgriLife Extension Service ENERGY STAR Appliances  

E-Print Network [OSTI]

Energy Star® Appliances 1 Texas A&M AgriLife Extension Service ENERGY STAR® Appliances ENERGY STAR®-labeled appliances save you money by using less electricity and water than other appliances. Better appliance energy efficiency comes from quality materials and technologically advanced materials. Although energy efficient

344

Photon emission from bare quark stars  

E-Print Network [OSTI]

We investigate the photon emission from the electrosphere of a quark star. It is shown that at temperatures T\\sim 0.1-1 MeV the dominating mechanism is the bremsstrahlung due to bending of electron trajectories in the mean Coulomb field of the electrosphere. The radiated energy for this mechanism is much larger than that for the Bethe-Heitler bremsstrahlung. The energy flux from the mean field bremsstrahlung exceeds the one from the tunnel e^{+}e^{-} pair creation as well. We demonstrate that the LPM suppression of the photon emission is negligible.

B. G. Zakharov

2010-08-16T23:59:59.000Z

345

Gravitomagnetism in superconductors and compact stars  

E-Print Network [OSTI]

There are three experimentally observed effects in rotating superconductors that are so far unexplained. Some authors have tried to interpret such a phenomena as possible new gravitational properties of coherent quantum systems: in particular, they suggest that the gravitomagnetic field of that kind of matter may be many orders of magnitude stronger than the one expected in the standard theory. Here I show that this interpretation would be in conflict with the common belief that neutron stars have neutrons in superfluid state and protons in superconductive one.

Cosimo Bambi

2007-10-10T23:59:59.000Z

346

Star Formation in the Local Universe  

E-Print Network [OSTI]

We present preliminary results of a long-term study aimed at answering a number of open questions on the evolution of starbursts in local galaxies. The project employes mainly HST data from the ultraviolet to the red of the stellar continuum and of the nebular emission from the galaxies. Here we concentrate on NGC5253 and NGC5236 (M83), that form a dwarf--massive galaxy pair at about 4 Mpc distance. The recent star formation history of the centers of the two galaxies is investigated in order to identify similarities and differences in the evolution of their central starbursts.

Daniela Calzetti; Jason Harris

2001-11-28T23:59:59.000Z

347

Front end electronics for the STAR TPC  

SciTech Connect (OSTI)

The Solenoidal Tracker at RHIC (STAR) is a large acceptance detector now being built to study high energy heavy ion collisions. It detects charged particles with a large time projection chamber. The 136,600 TPC pads are instrumented with waveform digitizers, implemented in custom low noise preamplifier/shaper and switched capacitor array/ADCs ICs. The system is highly integrated with all analog functions mounted on small cards that plug into the TPC. Detector mounted readout boards multiplex data from 1,152 channels onto a 1.5 Gbit/sec fiber optic link to the data acquisition system.

Klein, S.R.; Barale, P.; Beuville, E. [and others

1995-10-01T23:59:59.000Z

348

Holographic cold nuclear matter and neutron star  

E-Print Network [OSTI]

We have previously found a new phase of cold nuclear matter based on a holographic gauge theory, where baryons are introduced as instanton gas in the probe D8/$\\overline{\\rm D8}$ branes. In our model, we could obtain the equation of state (EOS) of our nuclear matter by introducing fermi momentum. Then, here we apply this model to the neutron star and study its mass and radius by solving the Tolman-Oppenheimer-Volkoff (TOV) equations in terms of the EOS given here. We give some comments for our holographic model from a viewpoint of the other field theoretical approaches.

Kazuo Ghoroku; Kouki Kubo; Motoi Tachibana; Fumihiko Toyoda

2014-02-19T23:59:59.000Z

349

Statistical Models and STAR's Strange Data  

E-Print Network [OSTI]

The yields of strange hadrons have been measured as a function of centrality in Au+Au and in $p+p$ collisions at $\\sqrt{s_{NN}}=200$ GeV in STAR. The system size and energy dependence are studied and compared for $p+p$ and Au+Au collisions. Thermal models are fitted to the ratios of various strange particles to investigate the particle production and to determine the strangeness enhancement. The temperatures ($T$) and the strangeness enhancement factors ($\\gamma_{s}$) of the systems determined from the fits are presented.

Sevil Salur

2006-06-01T23:59:59.000Z

350

Sound velocity bound and neutron stars  

E-Print Network [OSTI]

It has been conjectured that the velocity of sound in any medium is smaller than the velocity of light in vacuum divided by $\\sqrt{3}$. Simple arguments support this bound in non-relativistic and/or weakly coupled theories. The bound has been demonstrated in several classes of strongly coupled theories with gravity duals and is saturated only in conformal theories. We point out that the existence of neutron stars with masses around two solar masses combined with the knowledge of the equation of state of hadronic matter at "low" densities is in strong tension with this bound.

Paulo F. Bedaque; Andrew W. Steiner

2015-01-25T23:59:59.000Z

351

DarkStar VI | Open Energy Information  

Open Energy Info (EERE)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home5b9fcbce19 NoPublic Utilities Address:011-DNA Jump to: navigation, searchIllinois: Energy Resources Jump to: navigation,DarkStar

352

Compact boson stars in K field theories  

E-Print Network [OSTI]

We study a scalar field theory with a non-standard kinetic term minimally coupled to gravity. We establish the existence of compact boson stars, that is, static solutions with compact support of the full system with self-gravitation taken into account. Concretely, there exist two types of solutions, namely compact balls on the one hand, and compact shells on the other hand. The compact balls have a naked singularity at the center. The inner boundary of the compact shells is singular, as well, but it is, at the same time, a Killing horizon. These singular, compact shells therefore resemble black holes.

C. Adam; N. Grandi; P. Klimas; J. Sanchez-Guillen; A. Wereszczynski

2009-09-16T23:59:59.000Z

353

Compact boson stars in K field theories  

E-Print Network [OSTI]

We study a scalar field theory with a non-standard kinetic term minimally coupled to gravity. We establish the existence of compact boson stars, that is, static solutions with compact support of the full system with self-gravitation taken into account. Concretely, there exist two types of solutions, namely compact balls on the one hand, and compact shells on the other hand. The compact balls have a naked singularity at the center. The inner boundary of the compact shells is singular, as well, but it is, at the same time, a Killing horizon. These singular, compact shells therefore resemble black holes.

Adam, C; Klimas, P; Sánchez-Guillén, J; Wereszczynski, A

2009-01-01T23:59:59.000Z

354

Blue Star Energy Services | Open Energy Information  

Open Energy Info (EERE)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home5b9fcbce19 NoPublic Utilities Address: 160Benin: Energy ResourcesJersey:formBlue Energy Address: BoxBlueStar) Jump to:

355

Wave Star Energy | Open Energy Information  

Open Energy Info (EERE)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home5b9fcbce19 NoPublic Utilities Address: 160 East 300 South Place: Salt LakeWashtenawInformationTechnology New ZealandListStar

356

Five Star Technologies | Open Energy Information  

Open Energy Info (EERE)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home5b9fcbce19 NoPublicIDAPowerPlantSitingConstruction.pdfNotify98.pdf Jump to:Siting.pdfFiskdale,Five Star Technologies Jump to:

357

Star Energy Systems | Open Energy Information  

Open Energy Info (EERE)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data CenterFranconia, Virginia:FAQ < RAPID Jump to:Seadov Pty Ltd JumpGTZHolland,0162112°,St.Stanly County, North Carolina:Star Energy

358

StarSolar Corporation | Open Energy Information  

Open Energy Info (EERE)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data CenterFranconia, Virginia:FAQ < RAPID Jump to:Seadov Pty Ltd JumpGTZHolland,0162112°,St.Stanly County, NorthStarSolar Corporation Jump

359

All-Star Nanocrystals | The Ames Laboratory  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr MayAtmospheric Optical Depth (AOD)ProductssondeadjustsondeadjustAbout theOFFICE OF RESEARCHThermal Solar ThermalAll-Star Nanocrystals

360

STAR FORMATION IN NUCLEAR RINGS OF BARRED GALAXIES  

SciTech Connect (OSTI)

Nuclear rings in barred galaxies are sites of active star formation. We use hydrodynamic simulations to study the temporal and spatial behavior of star formation occurring in nuclear rings of barred galaxies where radial gas inflows are triggered solely by a bar potential. The star formation recipes include a density threshold, an efficiency, conversion of gas to star particles, and delayed momentum feedback via supernova explosions. We find that the star formation rate (SFR) in a nuclear ring is roughly equal to the mass inflow rate to the ring, while it has a weak dependence on the total gas mass in the ring. The SFR typically exhibits a strong primary burst followed by weak secondary bursts before declining to very small values. The primary burst is associated with the rapid gas infall to the ring due to the bar growth, while the secondary bursts are caused by re-infall of the ejected gas from the primary burst. While star formation in observed rings persists episodically over a few Gyr, the duration of active star formation in our models lasts for only about half of the bar growth time, suggesting that the bar potential alone is unlikely to be responsible for gas supply to the rings. When the SFR is low, most star formation occurs at the contact points between the ring and the dust lanes, leading to an azimuthal age gradient of young star clusters. When the SFR is large, on the other hand, star formation is randomly distributed over the whole circumference of the ring, resulting in no apparent azimuthal age gradient. Since the ring shrinks in size with time, star clusters also exhibit a radial age gradient, with younger clusters found closer to the ring. The cluster mass function is well described by a power law, with a slope depending on the SFR. Giant gas clouds in the rings have supersonic internal velocity dispersions and are gravitationally bound.

Seo, Woo-Young; Kim, Woong-Tae, E-mail: seowy@astro.snu.ac.kr, E-mail: wkim@astro.snu.ac.kr [Center for the Exploration of the Origin of the Universe (CEOU), Astronomy Program, Department of Physics and Astronomy, Seoul National University, Seoul 151-742 (Korea, Republic of)

2013-06-01T23:59:59.000Z

Note: This page contains sample records for the topic "waha lone star" 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

E-Print Network 3.0 - agb star ik Sample Search Results  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

LMC: Dust-enshrouded AGB stars, post-AGB stars and PN P.R. Wood Research School of Astronomy... . Spectra have been taken for most of the post-AGB stars and a selection of the...

362

E-Print Network 3.0 - autonomous star tracker Sample Search Results  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

of Vienna Delta Scuti Star Newsletter, Vol. 16?, 2001 Summary: ;eld monitor and a star tracker. Recently, it has been proven beyond doubt, that solar-type stars... as part of...

363

E-Print Network 3.0 - ae star hd Sample Search Results  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

field measurements of the Herbig Ae stars HD 101412 (left panel) and HD 150193 (right panel) (FORS 2... cool stars and solar-like stars Instrumentation The most successful...

364

E-Print Network 3.0 - ae star hd101412 Sample Search Results  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

field measurements of the Herbig Ae stars HD 101412 (left panel) and HD 150193 (right panel) (FORS 2... cool stars and solar-like stars Instrumentation The most successful...

365

TOPICAL REVIEW: General relativistic boson stars  

E-Print Network [OSTI]

There is accumulating evidence that (fundamental) scalar fields may exist in Nature. The gravitational collapse of such a boson cloud would lead to a boson star (BS) as a new type of a compact object. Similarly as for white dwarfs and neutron stars, there exists a limiting mass, below which a BS is stable against complete gravitational collapse to a black hole. According to the form of the self-interaction of the basic constituents and the spacetime symmetry, we can distinguish mini-, axidilaton, soliton, charged, oscillating and rotating BSs. Their compactness prevents a Newtonian approximation, however, modifications of general relativity, as in the case of Jordan-Brans-Dicke theory as a low energy limit of strings, would provide them with gravitational memory. In general, a BS is a compact, completely regular configuration with structured layers due to the anisotropy of scalar matter, an exponentially decreasing 'halo', a critical mass inversely proportional to constituent mass, an effective radius, and a large particle number. Due to the Heisenberg principle, there exists a completely stable branch, and as a coherent state, it allows for rotating solutions with quantised angular momentum. In this review, we concentrate on the fascinating possibilities of detecting the various subtypes of (excited) BSs: Possible signals include gravitational redshift and (micro-)lensing, emission of gravitational waves, or, in the case of a giant BS, its dark matter contribution to the rotation curves of galactic halos.

Franz E. Schunck; Eckehard W. Mielke

2008-01-01T23:59:59.000Z

366

Mutual Friction in Superfluid Neutron Stars  

E-Print Network [OSTI]

We discuss vortex-mediated mutual friction in the two-fluid model for superfluid neutron star cores. Our discussion is based on the general formalism developed by Carter and collaborators, which makes due distinction between transport velocity and momentum for each fluid. This is essential for an implementation of the so-called entrainment effect, whereby the flow of one fluid imparts momentum in the other and vice versa. The mutual friction follows by balancing the Magnus force that acts on the quantised neutron vortices with a resistive force due to the scattering of electrons off of the magnetic field with which each vortex core is endowed. We derive the form of the macroscopic mutual friction force which is relevant for a model based on smooth-averaging over a collection of vortices. We discuss the coefficients that enter the expression for this force, and the timescale on which the two interpenetrating fluids in a neutron star core are coupled. This discussion confirms that our new formulation accords well with previous work in this area.

N. Andersson; T. Sidery; G. L. Comer

2005-10-03T23:59:59.000Z

367

Gravitational lensing in eclipsing binary stars  

E-Print Network [OSTI]

I consider the effect of the gravitational deflection of light upon the light curves of eclipsing binary stars, focussing mainly upon systems containing at least one white dwarf component. In absolute terms the effects are small, however they are strongest at the time of secondary eclipse when the white dwarf transits its companion, and act to reduce the depth of this feature. If not accounted for, this may lead to under-estimation of the radius of the white dwarf compared to that of its companion. I show that the effect is significant for plausible binary parameters, and that it leads to ~25% reduction in the transit depth in the system KPD 1930+2752. The reduction of eclipse depth is degenerate with the stellar radius ratio, and therefore cannot be used to establish the existence of lensing. A second order effect of the light bending is to steepen the ingress and egress features of the secondary eclipse relative to the primary eclipse, although it will be difficult to see this in practice. I consider also binaries containing neutron stars and black-holes. I conclude that, although relatively large effects are possible in such systems, a combination of rarity, faintness and intrinsic variability make it unlikely that lensing will be detectable in them.

T. R. Marsh

2000-12-18T23:59:59.000Z

368

A Successful Targeted Search for Hypervelocity Stars  

E-Print Network [OSTI]

Hypervelocity stars (HVSs) travel with velocities so extreme that dynamical ejection from a massive black hole is their only suggested origin. Following our discovery of the first HVS, we have undertaken a dedicated survey for more HVSs in the Galactic halo and present here the resulting discovery of two new HVSs: SDSS J091301.0+305120 and SDSS J091759.5+672238, traveling with Galactic rest-frame velocities at least +558+-12 and +638+-12 km/s, respectively. Assuming the HVSs are B8 main sequence stars, they are at distances ~75 and ~55 kpc, respectively, and have travel times from the Galactic Center consistent with their lifetimes. The existence of two B8 HVSs in our 1900 deg^2 survey, combined with the Yu & Tremaine HVS rate estimates, is consistent with HVSs drawn from a standard initial mass function but inconsistent with HVS drawn from a truncated mass function like the one in the top-heavy Arches cluster. The travel times of the five currently known HVSs provide no evidence for a burst of HVSs from a major in-fall event at the Galactic Center in the last \\~160 Myr.

Warren R. Brown; Margaret J. Geller; Scott J. Kenyon; Michael J. Kurtz

2006-01-25T23:59:59.000Z

369

Heartbeat Stars and the Ringing of Tidal Pulsations Kelly Hambleton  

E-Print Network [OSTI]

Heartbeat Stars and the Ringing of Tidal Pulsations Kelly Hambleton Andrej Prsa, Don Kurtz, Jim Fuller, Susan Thompson University of Central Lancashire kmhambleton@uclan.ac.uk March 27, 2014 Kelly 3 Summary Conclusions Future Work Kelly Hambleton (UCLan) Heartbeat Stars March 27, 2014 2 / 33 #12

Â?umer, Slobodan

370

NEUTRON STAR ENVELOPES AND THERMAL RADIATION FROM THE MAGNETIC SURFACE  

E-Print Network [OSTI]

NEUTRON STAR ENVELOPES AND THERMAL RADIATION FROM THE MAGNETIC SURFACE in: C. Kouveliotou, J. van.Petersburg, Russia Abstract. The thermal structure of neutron star envelopes is discussed with emphasis on analytic on the opacities and the thermal structure is further reviewed in view of the application to pulsar cooling

371

Star-Forming Structures in Perseus Advisor: Prof. Alyssa Goodman  

E-Print Network [OSTI]

is a spectral energy dis- tribution (SED) shifted deep into the infrared, relative to a main sequence starStar-Forming Structures in Perseus Tom Laakso Advisor: Prof. Alyssa Goodman May 15th 2006 Abstract This year, both the Spitzer c2d legacy project and the COMPLETE survey have released new infrared

Harvard-Smithsonian Center for Astrophysics,

372

AN INFRARED CENSUS OF STAR FORMATION IN THE HORSEHEAD NEBULA  

SciTech Connect (OSTI)

At {approx} 400 pc, the Horsehead Nebula (B33) is the closest radiatively sculpted pillar to the Sun, but the state and extent of star formation in this structure is not well understood. We present deep near-infrared (IRSF/SIRIUS JHK {sub S}) and mid-infrared (Spitzer/IRAC) observations of the Horsehead Nebula to characterize the star-forming properties of this region and to assess the likelihood of triggered star formation. Infrared color-color and color-magnitude diagrams are used to identify young stars based on infrared excess emission and positions to the right of the zero-age main sequence, respectively. Of the 45 sources detected at both near- and mid-infrared wavelengths, three bona fide and five candidate young stars are identified in this 7' x 7' region. Two bona fide young stars have flat infrared spectral energy distributions and are located at the western irradiated tip of the pillar. The spatial coincidence of the protostars at the leading edge of this elephant trunk is consistent with the radiation-driven implosion model of triggered star formation. There is no evidence, however, for sequential star formation within the immediate {approx} 1.'5 (0.17 pc) region from the cloud/H II region interface.

Bowler, Brendan P. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Waller, William H. [Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States); Megeath, S. Thomas [Department of Physics and Astronomy, University of Toledo, Toledo, OH 43606 (United States); Patten, Brian M. [National Science Foundation, 4201 Wilson Blvd. Arlington, VA 22230 (United States); Tamura, Motohide [National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo 181-8588 (Japan)], E-mail: bpbowler@ifa.hawaii.edu, E-mail: william.waller@tufts.edu, E-mail: megeath@physics.utoledo.edu, E-mail: bpatten@nsf.gov, E-mail: motohide.tamura@nao.ac.jp

2009-03-15T23:59:59.000Z

373

THE STAR FORMATION LAW AT LOW SURFACE DENSITY  

SciTech Connect (OSTI)

We investigate the nature of the star formation law at low gas surface densities using a sample of 19 low surface brightness (LSB) galaxies with existing H I maps in the literature, UV imaging from the Galaxy Evolution Explorer satellite, and optical images from the Sloan Digital Sky Survey. All of the LSB galaxies have (NUV - r) colors similar to those for higher surface brightness star-forming galaxies of similar luminosity indicating that their average star formation histories are not very different. Based upon four LSB galaxies with both UV and far-infrared (FIR) data, we find FIR/UV ratios significantly less than 1, implying low amounts of internal UV extinction in LSB galaxies. We use the UV images and H I maps to measure the star formation rate (SFR) and hydrogen gas surface density within the same region for all the galaxies. The LSB galaxy star formation rate surface densities lie below the extrapolation of the power law fit to the SFR surface density as a function of the total gas density for higher surface brightness galaxies. Although there is more scatter, the LSB galaxies also lie below a second version of the star formation law in which the SFR surface density is correlated with the gas density divided by the orbital time in the disk. The downturn seen in both star formation laws is consistent with theoretical models that predict lower star formation efficiencies in LSB galaxies due to the declining molecular fraction with decreasing density.

Wyder, Ted K.; Martin, D. Christopher; Barlow, Tom A.; Foster, Karl; Friedman, Peter G.; Morrissey, Patrick; Neill, James D. [California Institute of Technology, MC 278-17, 1200 E. California Blvd., Pasadena, CA 91125 (United States); Neff, Susan G. [Laboratory for Astronomy and Solar Physics, NASA Goddard Space Flight Center, Greenbelt, MD, 20771 (United States); Schiminovich, David [Department of Astronomy, Columbia University, New York, NY 10027 (United States); Seibert, Mark; Madore, Barry F. [Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Bianchi, Luciana [Center for Astrophysical Sciences, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218 (United States); Donas, Jose; Milliard, Bruno [Laboratoire d'Astrophysique de Marseille, BP 8, Traverse du Siphon, 13376 Marseille Cedex 12 (France); Heckman, Timothy M.; Szalay, Alex S. [Department of Physics and Astronomy, Johns Hopkins University, Homewood Campus, Baltimore, MD 21218 (United States); Lee, Young-Wook; Yi, Sukyoung K. [Center for Space Astrophysics, Yonsei University, Seoul 120-749 (Korea, Republic of); Rich, R. Michael [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States)

2009-05-10T23:59:59.000Z

374

Some Observational Aspects of R Coronae Borealis Stars  

E-Print Network [OSTI]

Some of the observational aspects related to the evolutionary status and dust production in R Cor Bor stars are discussed. Recent work regarding the surface abundances, stellar winds and evidence for dust production in these high luminosty hydrogen deficient stars are also reviewed. Possibility of the stellar winds being maintained by surface magnetic fields is also considered.

N. Kameswara Rao

2007-12-24T23:59:59.000Z

375

Nuclear fusion in stars and laboratories April 1, 2002  

E-Print Network [OSTI]

Nuclear fusion in stars and laboratories April 1, 2002 1 Stellar structure and stellar energy 1 the ideal gas law and the fact that { from spectroscopy { we ¯nd that stars are overwhelmingly composed of H of energy. By the late 1930's it had become clear that this must be a nuclear energy source. ² Nuclear

Landstreet, John D.

376

Lithium in very metal poor thick disk stars  

E-Print Network [OSTI]

A search for lithium is performed on seven metal poor dwarfs with metallicities ranging from [Fe/H]=-1.5 down to [Fe/H]=-3.0 but showing disk-like kinematics. These stars belong to the metal poor tail of the Galactic thick disk and they may be also the result of an accretion event (Beers and Sommer-Larsen 1995). The Li 6707.8 A line is present in all the seven dwarfs. The weighted average of the Li abundance for the stars is A(Li)=2.20 (+/-0.06) and is consistent within the errors with the plateau Li abundance of A(Li)=2.24(+/- 0.012) found in genuine halo stars in the same range of metallicities (Bonifacio and Molaro 1997). One of the stars, CS 22182-24, shows somewhat lower Li abundance (A(Li)=1.6(+/-0.40)) and is a candidate to being a Li-poor star. Whether this group of stars belongs to the oldest stars in the disk or to the old population of an external galaxy accreted by the Milky Way, the present observations provide support to the universality of a pre-Galactic Li abundance as is observed in the Galactic halo stars.

P. Molaro; P. Bonifacio; L. Pasquini

1997-09-25T23:59:59.000Z

377

Savings Estimates for the ENERGY STAR Voluntary Labeling Program  

E-Print Network [OSTI]

. This paper presents past and predicted savings for the ENERGY STAR ® labeling program, operated jointly appliances. This report presents savings estimates for a subset of ENERGY STAR program activities, focused primarily on labeled products. We present estimates of the energy, dollar and carbon savings achieved

378

Making Sun-Earth Connections: Our Star Our Sun  

E-Print Network [OSTI]

1 Making Sun-Earth Connections: Our Star ­ Our Sun Presenter's Guide Grades: 3-5 #12;2 Making Sun-Earth Connections: Our Star ­ Our Sun Table of Contents: Slides and Captions: 1. Introduction and Space Exploration.........................................3 4. Structure of the Sun

Maxwell, Bruce D.

379

Utility Rebates for ENERGY STAR Appliances: Are They Effective?  

E-Print Network [OSTI]

Utility Rebates for ENERGY STAR Appliances: Are They Effective? Souvik Datta Sumeet Gulati CEPE;UTILITY REBATES FOR ENERGY STAR APPLIANCES: ARE THEY EFFECTIVE? SOUVIK DATTA ETH Z¨urich SUMEET GULATI by utility companies. To estimate the impact of these incentives we use the variation in timing and size

380

NEWS & VIEWS nEutRon StaRS  

E-Print Network [OSTI]

NEWS & VIEWS nEutRon StaRS a magnetar by another name Fernando Camilo is at the Columbia core, held stable by neutron degeneracy pressure -- with more mass than the Sun within a 10 km radius -- has central densities comparable to those of nuclei. What does the neutron star sky look like, made

Loss, Daniel

Note: This page contains sample records for the topic "waha lone star" 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

ISM dust feedback from low to high mass stars  

E-Print Network [OSTI]

The dust component of the interstellar medium (ISM) has been extensively studied in the past decades. Late-type stars have been assumed as the main source of dust to the ISM, but recent observations show that supernova remnants may play a role on the ISM dust feedback. In this work, I study the importance of low and high mass stars, as well as their evolutionary phase, on the ISM dust feedback process. I also determine the changes on the obtained results considering different mass distribution functions and star formation history. We describe a semi-empirical calculation of the relative importance of each star at each evolutionary phase in the dust ejection to the ISM. I compare the obtained results for two stellar mass distribution functions, the classic Salpeter initial mass function and the present day mass function. I used the evolutionary track models for each stellar mass, and the empirical mass-loss rates and dust-to-gas ratio. The relative contribution of each stellar mass depends on the used distribution. Ejecta from massive stars represent the most important objects for the ISM dust replenishment using the Salpeter IMF. On the other hand, for the present day mass function low and intermediate mass stars are dominant. Late-type giant and supergiant stars dominate the ISM dust feedback in our actual Galaxy, but this may not the case of galaxies experiencing high star formation rates, or at high redshifts. In those cases, SNe are dominant in the dust feedback process.

Falceta-Goncalves; D.

2007-10-26T23:59:59.000Z

382

Texas LoanSTAR Program Savings Calculation Workbook  

E-Print Network [OSTI]

This is the report and manual for the Texas LoanSTAR Program Savings Calculation Workbook. The purpose of this report is to document the Texas LoanSTAR Program Savings Calculation Workbook to be used by the State Energy Conservation Office (SECO...

Liu, Z.; Baltazar-Cervantes, J. C.; Haberl, J. S.

2003-01-01T23:59:59.000Z

383

X-ray Emission from Massive Stars David Cohen  

E-Print Network [OSTI]

X-ray Emission from Massive Stars David Cohen Department of Physics and Astronomy Swarthmore University, Oct. 13, 2005 astro.swarthmore.edu/~cohen/ #12;Outline 1. What you need to know: a. X-rays from the Sun - magnetic activity, x-ray spectra b. Hot stars c. Radiation-driven winds and the Doppler shift d

Cohen, David

384

E-Print Network 3.0 - agb stars radiative Sample Search Results  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Institut Potsdam, Stellar Physics Group Collection: Physics 11 Carbon-and Oxygen Stars in the IRAS Two-Color-Diagram Summary: Carbon- and Oxygen Stars in the IRAS...

385

E-Print Network 3.0 - ankle replacement star Sample Search Results  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

star Search Powered by Explorit Topic List Advanced Search Sample search results for: ankle replacement star Page: << < 1 2 3 4 5 > >> 1 BOSTON UNIVERSITY COLLEGE OF ENGINEERING...

386

SciTech Connect: The Nuclear Spectroscopic Telescope Array (NuSTAR...  

Office of Scientific and Technical Information (OSTI)

The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission Citation Details In-Document Search Title: The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission Authors: Harrison,...

387

Calendar Year 2007 Program Benefits for U.S. EPA Energy Star Labeled Products: Expanded Methodology  

E-Print Network [OSTI]

Administration, Office of Energy Markets and End Use.Administration, Office of Energy Markets and End Use.Total Shipments Star Energy Market Star Share Shipments

Sanchez, Marla

2010-01-01T23:59:59.000Z

388

Policy Flash 2015-06 Energy Star and Electronic Products Environmental...  

Energy Savers [EERE]

Policy Flash 2015-06 Energy Star and Electronic Products Environmental Assessment Tool (EPEAT) Policy Flash 2015-06 Energy Star and Electronic Products Environmental Assessment...

389

E-Print Network 3.0 - accretion stars Sample Search Results  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

accretion... transfer. Mass transfer manifests itself by accretion onto the star and windjet outflows while angular... rotation rate of young stars. ... Source: Ecole...

390

Three editions of the Star Catalogue of Tycho Brahe  

E-Print Network [OSTI]

Tycho Brahe completed his catalogue with the positions and magnitudes of 1004 fixed stars in 1598. This catalogue circulated in manuscript form. Brahe edited a shorter version with 777 stars, printed in 1602, and Kepler edited the full catalogue of 1004 stars, printed in 1627. We provide machine-readable versions of the three versions of the catalogue, describe the differences between them and briefly discuss their accuracy on the basis of comparison with modern data from the Hipparcos Catalogue. We also compare our results with earlier analyses by Dreyer (1916) and Rawlins (1993), finding good overall agreement. The magnitudes given by Brahe correlate well with modern values, his longitudes and latitudes have error distributions with widths of about 2 arcmin, with excess numbers of stars with larger errors (as compared to Gaussian distributions), in particular for the faintest stars. Errors in positions larger than 10 arcmin, which comprise about 15 per cent of the entries, are likely due to computing or cop...

Verbunt, Frank

2010-01-01T23:59:59.000Z

391

Beta Cephei stars in the inner part of the Galaxy  

E-Print Network [OSTI]

From the Fourier analysis of the catalogue of ~200,000 variable candidates in the OGLE-II Galactic fields, we found a sample of about 230 short-period low-amplitude variable stars. From their position in the colour-magnitude diagram and the observed periods (multiple in most cases), we identify the stars as a mixture of Beta Cephei and Delta Scuti stars. Beta Cephei stars from this sample are located in the Galactic disk at distances from 3 to 6 kpc. Many of them shows large range of the excited periods, an indication of high metallicity. We estimate that even a half of the sample of 230 short-period variables we found, can be Beta Cephei stars. The periods alone, however, are rarely sufficient to distinguish between both types of pulsators. We point out, how this can be done observationally.

A. Narwid; Z. Kolaczkowski; A. Pigulski; T. Ramza

2005-10-04T23:59:59.000Z

392

Nuclear Star Clusters in Edge-on Galaxies  

E-Print Network [OSTI]

From observations of edge-on, late-type galaxies, we present morphological evidence that some nuclear star clusters have experienced in situ star formation. We find three nuclear clusters that, viewed from the edge-on perspective, have both a compact disk-like component and a spheroidal component. In each cluster, the disk components are closely aligned with the major axis of the host galaxy and have bluer colors than the spheroidal components. We spectroscopically verify that one of the observed multiple component clusters has multiple generations of stars. These observations lead us to suggest a formation mechanism for nuclear star clusters, in which stars episodically form in compact nuclear disks, and then lose angular momentum, eventually forming an older spheroid.

Anil C. Seth; Julianne J. Dalcanton; Paul W. Hodge; Victor P. Debattista

2006-06-02T23:59:59.000Z

393

STAR (Solenoidal Tracker at RHIC) Figures and Data  

DOE Data Explorer [Office of Scientific and Technical Information (OSTI)]

The primary physics task of STAR is to study the formation and characteristics of the quark-gluon plasma (QGP), a state of matter believed to exist at sufficiently high energy densities. STAR consists of several types of detectors, each specializing in detecting certain types of particles or characterizing their motion. These detectors work together in an advanced data acquisition and subsequent physics analysis that allows final statements to be made about the collision. The STAR Publications page provides access to all published papers by the STAR Collaboration, and many of them have separate links to the figures and data found in or supporting the paper. See also the data-rich summaries of the research at http://www.star.bnl.gov/central/physics/results/. [See also DDE00230

The STAR Collaboration

394

The Age and Interior Rotation of Stars from Asteroseismology  

E-Print Network [OSTI]

We provide a status report on the determination of stellar ages from asteroseismology for stars of various masses and evolutionary stages. The ability to deduce the ages of stars with a relative precision of typically 10 to 20% is a unique opportunity for stellar evolution and also of great value for both galactic and exoplanet studies. Further, a major uncalibrated ingredient that makes stellar evolution models uncertain, is the stellar interior rotation frequency $\\Omega(r)$ and its evolution during stellar life. We summarize the recent achievements in the derivation of $\\Omega(r)$ for different types stars, offering stringent observational constraints on theoretical models. Core-to-envelope rotation rates during the red giant stage are far lower than theoretical predictions, pointing towards the need to include new physical ingredients that allow strong and efficient coupling between the core and the envelope in the models of low-mass stars in the evolutionary phase prior to the core helium burning. Stars ...

Aerts, Conny

2015-01-01T23:59:59.000Z

395

Cloud and Star Formation in Disk Galaxy Models with Feedback  

E-Print Network [OSTI]

We include feedback in global hydrodynamic simulations in order to study the star formation properties, and gas structure and dynamics, in models of galactic disks. We extend previous models by implementing feedback in gravitationally bound clouds: momentum is injected at a rate proportional to the star formation rate. This mechanical energy disperses cloud gas back into the surrounding ISM, truncating star formation in a given cloud, and raising the overall level of ambient turbulence. Propagating star formation can however occur as expanding shells collide, enhancing the density and triggering new cloud and star formation. By controlling the momentum injection per massive star and the specific star formation rate in dense gas, we find that the negative effects of high turbulence outweigh the positive ones, and in net feedback reduces the fraction of dense gas and thus the overall star formation rate. The properties of the large clouds that form are not, however, very sensitive to feedback, with cutoff masses of a few million solar masses, similar to observations. We find a relationship between the star formation rate surface density and the gas surface density with a power law index ~2 for our models with the largest dynamic range, consistent with theoretical expectations for our model of disk flaring. We point out that the value of the "Kennicutt-Schmidt" index depends on the thickness of the disk. With our simple feedback prescription (a single combined star formation event per cloud), we find that global spiral patterns are not sustained; less correlated feedback and smaller scale turbulence appear to be necessary for spiral patterns to persist.

Rahul Shetty; Eve C. Ostriker

2008-05-26T23:59:59.000Z

396

A SAMPLE OF CANDIDATE RADIO STARS IN FIRST AND SDSS  

SciTech Connect (OSTI)

We conduct a search for radio stars by combining radio and optical data from the FIRST survey and the Sloan Digital Sky Survey (SDSS). The faint limit of SDSS makes possible a homogeneous search for radio emission from stars of low optical luminosity. We select a sample of 112 candidate radio stars in the magnitude range 15 < i {approx}< 19.1 and with radio flux S {sub 20} {>=} 1.25 mJy, from about 7000 deg{sup 2} of sky. The selection criteria are positional coincidence within 1'', radio and optical point source morphology, and an SDSS spectrum classified as stellar. The sample contamination is estimated by random matching to be 108 {+-} 13, suggesting that at most a small fraction of the selected candidates are genuine radio stars. Therefore, we rule out a very rare population of extremely radio-loud stars: no more than 1.2 of every million stars in the magnitude range 15 < i < 19.1 stars has radio flux S {sub 20} {>=} 1.25 mJy. We investigate the optical and radio colors of the sample to find candidates that show the largest likelihood of being real radio stars. The significant outliers from the stellar locus, as well as the magnetically active stars, are the best candidates for follow-up radio observations. We conclude that, while the present wide-area radio surveys are not sensitive enough to provide homogeneous samples of the extremely rare radio stars, upcoming surveys that exploit the great sensitivity of current and planned telescopes do have sufficient sensitivity and will allow the properties of this class of object to be investigated in detail.

Kimball, Amy E.; Ivezic, Zeljko; Plotkin, Richard M. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195-1580 (United States); Knapp, Gillian R.; Gordon, Michael S. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); West, Andrew A.; Bochanski, John J. [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)], E-mail: akimball@astro.washington.edu

2009-08-10T23:59:59.000Z

397

X-ray Emission from Massive StarsX-ray Emission from Massive Stars David CohenDavid Cohen  

E-Print Network [OSTI]

X-ray Emission from Massive StarsX-ray Emission from Massive Stars David CohenDavid Cohen/s)Velocity (km/s) #12;absorption emission emission occulted emission emission UV telescope side side front back #12;absorption emission emission occulted emission emission UV telescope side side front back #12;The

Cohen, David

398

Mid-Infrared Spectra of Be Stars  

E-Print Network [OSTI]

We present the first medium-resolution ($R\\sim 600$) mid-infrared (8-13.3\\micron) spectra of 11 Be stars. A large number of lines are observed and identified in these spectra, including, as an example, 39 hydrogen recombination lines in the spectrum of $\\gamma$ Cas. In the majority of our spectra, all of the observed lines are attributable to hydrogen recombination. Two of the sources, $\\beta$ Lyr and MWC 349 also show emission from other species. Both of these objects show evidence of [Ne II] emission, and $\\beta$ Lyr also shows evidence of He I emission. We tabulate the effective line strength and line widths for the observed lines, and briefly discuss the physical implications of the observed line series. We also use a simple model of free-free emission to characterize the disks around these sources.

S. A. Rinehart; J. R. Houck; J. D. Smith

1999-10-11T23:59:59.000Z

399

The Star Formation Density at z=7  

E-Print Network [OSTI]

Near-infrared VLT data of the GOODS-South area were used to look for galaxies at z=7 down to a limiting magnitude of (J+Ks)AB=25.5. No high-redshift candidates were detected, and this provides clear evidence for a strong evolution of the luminosity function between z=6 and z=7, i.e. over a time interval of only 170 Myr. Our constraints provide evidence of a significant decline in the total star formation rate at z=7, which must be less than 40% of that at z=3 and 40-80% of that at z=6. The resulting upper limit to the ionizing flux at z=7 is only marginally consistent with what is required to completely ionize the Universe.

F. Mannucci

2006-11-29T23:59:59.000Z

400

On rotationally driven meridional flows in stars  

E-Print Network [OSTI]

A quasi-steady state model of the consequences of rotation on the hydrodynamical structure of a stellar radiative zone is derived, by studying in particular the role of centrifugal and baroclinic driving of meridional motions in angular-momentum transport. This nonlinear problem is solved numerically assuming axisymmetry of the system, and within some limits, it is shown that there exist simple analytical solutions. The limit of slow rotation recovers Eddington-Sweet theory, whereas it is shown that in the limit of rapid rotation, the system settles into a geostrophic equilibrium. The behaviour of the system is found to be controlled by one parameter only, linked to the Prantl number, the stratification and the rotation rate of the star.

P. Garaud

2002-03-21T23:59:59.000Z

Note: This page contains sample records for the topic "waha lone star" 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.


401

Star-Formation Knots in IRAS Galaxies  

E-Print Network [OSTI]

Images of IRAS galaxies with a range of IR properties are examined for bright knots, both within and outside the galaxy. These are found almost exclusively in galaxies with steep IR spectra, but over a wide range of IR luminosity, and usually without strong nuclear activity. In most cases, the knots are likely to be star-formation induced by tidal interactions, and are seen in the early stages of such interactions. Detailed photometry is presented of knots in six representative galaxies. The knots appear to have a wide range of colour and luminosity, but it is argued that many are heavily reddened. Knots formed outside the parent galaxy may be a new generation of what later become globular clusters, but they appear to have a wide range of luminosities.

J. B. Hutchings

1995-11-08T23:59:59.000Z

402

Relativistic MHD Winds from Rotating Neutron Stars  

E-Print Network [OSTI]

We solve the time-dependent dynamics of axisymmetric, general relativistic MHD winds from rotating neutron stars. The mass loss rate is obtained self consistently as a solution of the MHD equations, subject to a finite thermal pressure at the stellar surface. Conditions are chosen to be representative of the neutrino driven phase in newly born magnetars, which have been considered as a possible engine for GRBs. We compute the angular momentum and energy losses as a function of $\\sigma$ and compare them with the analytic expectation from the classical theory of pulsar winds. We observe the convergence to the force-free limit in the energy loss and we study the evolution of the closed zone for increasing magnetization. Results also show that the dipolar magnetic field and the presence of a closed zone do not modify significantly the acceleration and collimation properties of the wind.

N. Bucciantini; T. A. Thompson; J. Arons; E. Quataert

2006-12-22T23:59:59.000Z

403

Chemical Evolution of the Galactic Halo through Supernova-Induced Star Formation and Its Implication for Population III Stars  

E-Print Network [OSTI]

A model for Galactic chemical evolution, driven by supernova-induced star formation, is formulated and used to examine the nature of the Galactic halo at early epochs. In this model, new stars are formed following each supernova event, thus their abundance pattern is determined by the combination of heavy elements ejected from the supernova itself and those elements which are already present in the interstellar gas swept up by the supernova remnant. The end result is a prediction of large scatter in the abundance ratios among low-metallicity stars, reflecting a different nucleosynthesis yield for each Type II supernova with a different progenitor mass. Formation of new stars is terminated when supernova remnants sweep up too little gas to form shells. We show from calculations based on the above scenario that (i) the observed [Fe/H] distribution for the Galactic halo field stars can be reproduced without effectively decreasing the heavy-element yields from Type II supernovae by some manipulation required by previous models (e.g., via mass loss from the early Galaxy, or later mixing with ``pristine'' hydrogen clouds), (ii) the large observed scatter in the abundance ratio [Eu/Fe] for the most metal-poor stars can also be reproduced, and (iii) the frequency distribution of stars in the [Eu/Fe]-[Fe/H] plane can be predicted. Our model suggests that the probability of identifying essentially metal-free stars (Population III) in the local halo is around one in 10^{3-4}, provided that star formation in the halo is confined to individual gas clouds with mass of 10^{6-7} Msun and that the initial mass function of metal-free stars is not significantly different from the Salpeter mass function.

Takuji Tsujimoto; Toshikazu Shigeyama; Yuzuru Yoshii

1999-05-06T23:59:59.000Z

404

FORMING AN O STAR VIA DISK ACCRETION?  

SciTech Connect (OSTI)

We present a study of outflow, infall, and rotation in a {approx}10{sup 5} L{sub Sun} star-forming region, IRAS 18360-0537, with Submillimeter Array and IRAM 30 m observations. The 1.3 mm continuum map shows a 0.5 pc dust ridge, of which the central compact part has a mass of {approx}80 M{sub Sun} and harbors two condensations, MM1 and MM2. The CO (2-1) and SiO (5-4) maps reveal a biconical outflow centered at MM1, which is a hot molecular core (HMC) with a gas temperature of 320 {+-} 50 K and a mass of {approx}13 M{sub Sun }. The outflow has a gas mass of 54 M{sub Sun} and a dynamical timescale of 8 Multiplication-Sign 10{sup 3} yr. The kinematics of the HMC are probed by high-excitation CH{sub 3}OH and CH{sub 3}CN lines, which are detected at subarcsecond resolution and unveil a velocity gradient perpendicular to the outflow axis, suggesting a disk-like rotation of the HMC. An infalling envelope around the HMC is evidenced by CN lines exhibiting a profound inverse P Cygni profile, and the estimated mass infall rate, 1.5 Multiplication-Sign 10{sup -3} M{sub Sun} yr{sup -1}, is well comparable to that inferred from the mass outflow rate. A more detailed investigation of the kinematics of the dense gas around the HMC is obtained from the {sup 13}CO and C{sup 18}O (2-1) lines; the position-velocity diagrams of the two lines are consistent with the model of a free-falling and Keplerian-like rotating envelope. The observations suggest that the protostar of a current mass {approx}10 M{sub Sun} embedded within MM1 will develop into an O star via disk accretion and envelope infall.

Qiu Keping [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany); Zhang Qizhou [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Beuther, Henrik; Fallscheer, Cassandra, E-mail: kqiu@mpifr-bonn.mpg.de [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany)

2012-09-10T23:59:59.000Z

405

Bose-Einstein Condensate general relativistic stars  

E-Print Network [OSTI]

We analyze the possibility that due to their superfluid properties some compact astrophysical objects may contain a significant part of their matter in the form of a Bose-Einstein condensate. To study the condensate we use the Gross-Pitaevskii equation, with arbitrary non-linearity. By introducing the Madelung representation of the wave function, we formulate the dynamics of the system in terms of the continuity equation and of the hydrodynamic Euler equations. The non-relativistic and Newtonian Bose-Einstein gravitational condensate can be described as a gas, whose density and pressure are related by a barotropic equation of state. In the case of a condensate with quartic non-linearity, the equation of state is polytropic with index one. In the framework of the Thomas-Fermi approximation the structure of the Newtonian gravitational condensate is described by the Lane-Emden equation, which can be exactly solved. The case of the rotating condensate is also discussed. General relativistic configurations with quartic non-linearity are studied numerically with both non-relativistic and relativistic equations of state, and the maximum mass of the stable configuration is determined. Condensates with particle masses of the order of two neutron masses (Cooper pair) and scattering length of the order of 10-20 fm have maximum masses of the order of 2 M_sun, maximum central density of the order of 0.1-0.3 10^16 g/cm^3 and minimum radii in the range of 10-20 km. In this way we obtain a large class of stable astrophysical objects, whose basic astrophysical parameters (mass and radius) sensitively depend on the mass of the condensed particle, and on the scattering length. We also propose that the recently observed neutron stars with masses in the range of 2-2.4 M_sun are Bose-Einstein Condensate stars.

P. H. Chavanis; T. Harko

2011-08-19T23:59:59.000Z

406

Bipolar Outflows and the Evolution of Stars  

E-Print Network [OSTI]

Hypersonic bipolar outflows are a ubiquitous phenomena associated with both young and highly evolved stars. Observations of Planetary Nebulae, the nebulae surrounding Luminous Blue Variables such as $\\eta$ Carinae, Wolf Rayet bubbles, the circumstellar environment of SN 1987A and Young Stellar Objects all revealed high velocity outflows with a wide range of shapes. In this paper I review the current state of our theoretical understanding of these outflows. Beginning with Planetary Nebulae considerable progress has been made in understanding bipolar outflows as the result of stellar winds interacting with the circumstellar environment. In what has been called the "Generalized Wind Blown Bubble" (GWBB) scenario, a fast tenuous wind from the central star expands into a ambient medium with an aspherical (toroidal) density distribution. Inertial gradients due to the gaseous torus quickly lead to an expanding prolate or bipolar shell of swept-up gas bounded by strong shock waves. Numerical simulations of the GWBB scenario show a surprisingly rich variety of gasdynamical behavior, allowing models to recover many of the observed properties of stellar bipolar outflows including the development of collimated supersonic jets. In this paper we review the physics behind the GWBB scenario in detail and consider its strengths and weakness. Alternative models involving MHD processes are also examined. Applications of these models to each of the principle classes of stellar bipolar outflow (YSO, PNe, LBV, SN87A) are then reviewed. Outstanding issues in the study of bipolar outflows are considered as are those questions which arise when the outflows are viewed as a single class of phenomena occuring across the HR diagram.

Adam Frank

1998-05-20T23:59:59.000Z

407

Two-Dimensional Hydrodynamic Models of Super Star Clusters with a Positive Star Formation Feedback  

E-Print Network [OSTI]

Using the hydrodynamic code ZEUS, we perform 2D simulations to determine the fate of the gas ejected by massive stars within super star clusters. It turns out that the outcome depends mainly on the mass and radius of the cluster. In the case of less massive clusters, a hot high velocity ($\\sim 1000$ km s$^{-1}$) stationary wind develops and the metals injected by supernovae are dispersed to large distances from the cluster. On the other hand, the density of the thermalized ejecta within massive and compact clusters is sufficiently large as to immediately provoke the onset of thermal instabilities. These deplete, particularly in the central densest regions, the pressure and the pressure gradient required to establish a stationary wind, and instead the thermally unstable parcels of gas are rapidly compressed, by a plethora of re-pressurizing shocks, into compact high density condensations. Most of these are unable to leave the cluster volume and thus accumulate to eventually feed further generations of star for...

Wünsch, R; Palous, J; Silich, S

2008-01-01T23:59:59.000Z

408

Discovery of hot supergiant stars near the Galactic center  

E-Print Network [OSTI]

We report new results of a campaign to find Wolf-Rayet and O (WR/O) stars and high-mass X-ray binaries (HMXBs) in the Galactic center. We searched for candidates by cross-correlating the 2MASS catalog with a deep Chandra catalog of X-ray point sources in the Radio Arches region. Following up with K-band spectroscopy, we found two massive stellar counterparts to CXOGC J174555.3-285126 and CXOGC J174617.0-285131, which we classify as a broad-lined WR star of sub-type WN6b and an O Ia supergiant, respectively. Their X-ray properties are most consistent with those of known colliding-wind binaries in the Galaxy and the Large Magellanic Cloud, although a scenario involving low-rate accretion onto a compact object is also possible. The O Ia star lies 4.4 pc in projection from the Quintuplet cluster, and has a radial velocity consistent with that of the Quintuplet, suggesting that this star might have escaped from the cluster. We also present the discovery of a B2 Ia supergiant, which we identified as a candidate massive star using 8 micron Spitzer maps of the Galactic center in a region near the known massive X-ray-emitting star CXOGC J174516.1-290315. We discuss the origin of these stars in the context of evolving stellar clusters in the Galactic center.

Jon C. Mauerhan; Michael P. Muno; Mark Morris

2007-03-08T23:59:59.000Z

409

The Era of Star Formation in Galaxy Clusters  

E-Print Network [OSTI]

We analyze the star formation properties of 16 infrared-selected, spectroscopically confirmed galaxy clusters at $1 1.35$. Using infrared luminosities measured with deep Spitzer/MIPS observations at 24 $\\mu$m, along with robust optical+IRAC photometric redshifts and SED-fitted stellar masses, we present the dust-obscured star-forming fractions, star formation rates and specific star formation rates in these clusters as functions of redshift and projected clustercentric radius. We find that $z\\sim 1.4$ represents a transition redshift for the ISCS sample, with clear evidence of an unquenched era of cluster star formation at earlier times. Beyond this redshift the fraction of star-forming cluster members increases monotonically toward the cluster centers. Indeed, the specific star formation rate in the cores of these distant clusters is consistent with field values at similar redshifts, indicating that at $z>1.4$ environment-dependent quenching had not yet been established in ISCS clusters. Combining these obse...

Brodwin, M; Gonzalez, Anthony H; Zeimann, G R; Snyder, G F; Mancone, C L; Pope, A; Eisenhardt, P R; Stern, D; Alberts, S; Ashby, M L N; Brown, M J I; Chary, R -R; Dey, Arjun; Galametz, A; Gettings, D P; Jannuzi, B T; Miller, E D; Moustakas, J; Moustakas, L A

2013-01-01T23:59:59.000Z

410

The rotational behavior of Kepler Stars with Planets  

E-Print Network [OSTI]

We analyzed the host stars of the present sample of confirmed planets detected by Kepler and Kepler Objects of Interest (KOI) to compute new photometric rotation periods and to study the behavior of their angular momentum. Lomb-Scargle periodograms and wavelet maps were computed for 3,807 stars. For 540 of these stars, we were able to detect rotational modulation of the light curves at a significance level of greater than 99%. For 63 of these 540 stars, no rotation measurements were previously available in the literature. According to the published masses and evolutionary tracks of the stars in this sample, the sample is composed of M- to F-type stars (with masses of 0.48-1.53 M$_{\\odot}$) with rotation periods that span a range of 2 to 89 days. These periods exhibit an excellent agreement with previously reported (for the stars for which such values are available), and the observed rotational period distribution strongly agrees with theoretical predictions. Furthermore, for the 540 sources considered here, t...

Paz-Chinchón, F; Bravo, J P; de Freitas, D B; Lopes, C E Ferreira; Alves, S; Catelan, M; Martins, B L Canto; De Medeiros, J R

2015-01-01T23:59:59.000Z

411

Close encounters involving free-floating planets in star clusters  

E-Print Network [OSTI]

Instabilities in planetary systems can result in the ejection of planets from their host system, resulting in free-floating planets (FFPs). If this occurs in a star cluster, the FFP may remain bound to the star cluster for some time and interact with the other cluster members until it is ejected. Here, we use $N$-body simulations to characterise close star-planet and planet-planet encounters and the dynamical fate of the FFP population in star clusters containing $500-2000$ single or binary star members. We find that FFPs ejected from their planetary system at low velocities typically leave the star cluster 40% earlier than their host stars, and experience tens of close ($planets before they escape. The fraction of FFPs that experiences a close encounter depends on both the stellar density and the initial velocity distribution of the FFPs. Approximately half of the close encounters occur within the first 30 Myr, and only 10% occur after 100 Myr. The periastron vel...

Wang, Long; Zheng, Xiaochen; Church, Ross P; Davies, Melvyn B

2015-01-01T23:59:59.000Z

412

A Bcool magnetic snapshot survey of solar-type stars  

E-Print Network [OSTI]

Stellar magnetic field measurements obtained from spectropolarimetry offer key data for activity and dynamo studies, and we present the results of a major high-resolution spectropolarimetric Bcool project magnetic snapshot survey of 170 solar-type stars from observations with the Telescope Bernard Lyot and the Canada-France-Hawaii Telescope. For each target star a high signal-to-noise circularly polarised Stokes V profile has been obtained using Least-Squares Deconvolution, and used to detect surface magnetic fields and measure the corresponding mean surface longitudinal magnetic field ($B_{l}$). Chromospheric activity indicators were also measured. Surface magnetic fields were detected for 67 stars, with 21 of these stars classified as mature solar-type stars, a result that increases by a factor of four the number of mature solar-type stars on which magnetic fields have been observed. In addition, a magnetic field was detected for 3 out of 18 of the subgiant stars surveyed. For the population of K-dwarfs the...

Marsden, S C; Jeffers, S V; Morin, J; Fares, R; Reiners, A; Nascimento, J D do; Auriere, M; Bouvier, J; Carter, B D; Catala, C; Dintrans, B; Donati, J -F; Gastine, T; Jardine, M; Konstantinova-Antova, R; Lanoux, J; Lignieres, F; Morgenthaler, A; Ramirez-Velez, J C; Theado, S; Van Grootel, V

2013-01-01T23:59:59.000Z

413

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

414

Some recent results for the roAp stars  

E-Print Network [OSTI]

Three topics are discussed: 1) Photometric observations of the rapidly oscillating Ap stars have shown that the pulsation amplitude drops dramatically as a function of wavelength from the blue to the red. A theoretical derivation, plus modelling, indicates that this is because the vertical wavelength of the pulsation mode is short compared to the scale height of the atmosphere; in fact, it indicates that we are seeing a pulsation node in the observable atmosphere. Radial velocity observations, and theoretical calculations now support this. The implication for other research on CP stars is that this can provide observational constraints on the atmospheric structure independent of traditional spectral analysis. 2) Luminosities of roAp stars can be determined from asteroseismology. A recent comparison of such asteroseismic luminosities with HIPPARCOS luminosities is shown. This suggests that roAp stars have lower temperatures and/or smaller radii than previous models have used, or that the magnetic fields in these stars alter the frequency separations. 3) The latest results of our long-term monitoring of the pulsation frequencies in certain roAp stars are discussed. There is a clear cyclic variability to the pulsation cavity, hence the sound speed and/or sound travel time (radius) of these stars. This might be indicative of magnetic cycles at a level that magnetic measurements cannot currently detect, although there is no theoretical support for such an idea.

D. W. Kurtz

1998-05-05T23:59:59.000Z

415

GAMMA RAYS FROM STAR FORMATION IN CLUSTERS OF GALAXIES  

SciTech Connect (OSTI)

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

416

Which Massive stars are Gamma-Ray Burst Progenitors?  

E-Print Network [OSTI]

The collapsar model for gamma-ray bursts requires three essential ingredients: a massive core, removal of the hydrogen envelope, and enough angular momentum in the core. We study current massive star evolution models of solar metallicity to determine which massive star physics is capable of producing these ingredients. In particular, we investigate the role of hydrodynamic and magnetic internal angular momentum transport and binary mass and angular momentum transfer. We follow the evolution of rotating single stars and of binary systems that include rotational processes for both stars. Neglecting magnetic fields, we show that the cores of massive single stars can maintain a high specific angular momentum when evolved with the assumption that mean molecular weight gradients suppress rotational mixing processes. In binary systems that undergo mass transfer during core hydrogen burning the mass receiving star accretes large amounts of high angular momentum material, leading to a spin-up of the core. We find, however, that this merely compensates for the tidal angular momentum loss due to spin-orbit coupling, which leads to synchronous rotation before the mass transfer event. Therefore the resulting cores do not rotate faster than in single stars. We also present models that include magnetic fields generated by differential rotation and we consider the internal angular momentum transport by magnetic torques. We investigate the capability of magnetic torques to efficiently pump angular momentum into the cores of accreting stars. Despite our finding that this mechanism works, the magnetic coupling of core and envelope after the accreting star ends core hydrogen burning leads to slower rotation than in the non-magnetic case.

Jelena Petrovic; Norbert Langer; Sung-Chul Yoon; Alexander Heger

2005-04-11T23:59:59.000Z

417

The role of magnetic fields in hyperon stars  

SciTech Connect (OSTI)

We investigate the effects of strong magnetic fields (SMF) on the properties of neutron stars that have hyperons in their composition. The matter is described by a hadronic model in which a parameterized and derivative coupling between hadrons and mesons is considered. We study the magnetic effects on the equation of state (EoS) from Landau quantization, assuming a density dependent static magnetic field that reaches 10{sup 19} G in the center of the star. The Tolman- Oppenheimer-Volkoff (TOV) equations are solved in order to show the dependence of the massradius relation and population of hyperon stars on the central magnetic field and on different hyperon coupling schemes.

Gomes, R. O.; Vasconcellos, C. A. Z. [Instituto de Física - Universidade Federal do Rio Grande do Sul, Porto Alegre, RS 91501-970 (Brazil); Dexheimer, V. [Department of Physics - Kent State University, Kent, OH 44242 (United States)

2014-05-09T23:59:59.000Z

418

Kaon condensation in neutron star using relativistic mean field models  

E-Print Network [OSTI]

We use the modified quark-meson coupling and the quantum hadrodynamics models to study the properties of neutron star. Coupling constants of both models are adjusted to reproduce the same saturation properties. The onset of kaon condensation in neutron star matter is studied in detail over a wide range of kaon optical potential values. Once the kaon condensation takes place, the population of kaons increases very rapidly, and kaons become the dominant component, possibly making the neutron star matter a kaonic matter if the kaon optical potential is large.

S. W. Hong; C. H. Hyun; C. Y. Ryu

2007-02-08T23:59:59.000Z

419

Massive binaries, Wolf-Rayet stars and supernova progenitors  

E-Print Network [OSTI]

Binary stars are important for a full understanding of stellar evolution. We present a summary of how predictions of the relative supernova rates varies between single and binary stars. We also show how the parameter space of different supernova types differs between single and binary stars. We then consider an important question of how to infer a supernova progenitor's properties from pre-explosion imaging and present rescent work of producing synthe tic colours for our stellar models to make a direct comparison with any detections or limits obtained on supernova progentiors from pre-explosion images.

J. J. Eldridge

2006-12-17T23:59:59.000Z

420

Novel Geometrical Models of Relativistic Stars. I. The General Scheme  

E-Print Network [OSTI]

In a series of articles we describe a novel class of geometrical models of relativistic stars. Our approach to the static spherically symmetric solutions of Einstein equations is based on a careful physical analysis of radial gauge conditions. It brings us to a two parameter family of relativistic stars without stiff functional dependence between the stelar radius and stelar mass. It turns out that within this family there do exist relativistic stars with arbitrary large mass, which are to have arbitrary small radius and arbitrary small luminosity. In addition, point particle idealization, as a limiting case of bodies with finite dimension, becomes possible in GR, much like in Newton gravity.

P. P. Fiziev

2004-09-19T23:59:59.000Z

Note: This page contains sample records for the topic "waha lone star" 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

Solar-like oscillations in a massive star  

E-Print Network [OSTI]

Seismology of stars provides insight into the physical mechanisms taking place in their interior, with modes of oscillation probing different layers. Low-amplitude acoustic oscillations excited by turbulent convection were detected four decades ago in the Sun and more recently in low-mass main-sequence stars. Using data gathered by the Convection Rotation and Planetary Transits mission, we report here on the detection of solar-like oscillations in a massive star, V1449 Aql, which is a known large-amplitude (b Cephei) pulsator.

Belkacem, K; Goupil, M -J; Lefèvre, L; Baudin, F; Deheuvels, S; Dupret, M -A; Appourchaux, T; Scuflaire, R; Auvergne, M; Catala, C; Michel, E; Miglio, A; Montalban, J; Thoul, A; Talon, S; Baglin, A; Noels, A

2009-01-01T23:59:59.000Z

422

Massive zero-metal stars: Energy production and mixing  

E-Print Network [OSTI]

Time-dependent nuclear network calculations at constant temperature show that for zero-metal stars >= 20 Msun (i) beta-decay reactions and (ii) the 13N(p,gamma)14O reaction must be included. It is also shown that the nuclear timescale in these zero-metal stars is shorter than the mixing timescale and therefore the assumption of instantaneous mixing across convective regions is not fulfilled. We conclude that proper modeling of these processes may alter the evolution of massive zero-metal stars.

C. W. Straka; W. M. Tscharnuter

2001-03-21T23:59:59.000Z

423

Star Formation and the Growth of Stellar Mass  

E-Print Network [OSTI]

Recent observations have demonstrated a significant growth in the integrated stellar mass of the red sequence since z=1, dominated by a steadily increasing number of galaxies with stellar masses M* 3x10^10 M_sun blue galaxies would also be overproduced; i.e., most of the new stars formed in blue cloud galaxies are in the massive galaxies. We explore a simple truncation scenario in which these `extra' blue galaxies have their star formation suppressed by an unspecified mechanism or mechanisms; simple cessation of star formation in these extra blue galaxies is approximately sufficient to build up the red sequence at M*<10^11 M_sun.

Eric F. Bell; Xian Zhong Zheng; Casey Papovich; Andrea Borch; Christian Wolf; Klaus Meisenheimer

2007-04-23T23:59:59.000Z

424

15 colour photometry of Landolt SA95 standard star field  

E-Print Network [OSTI]

In this paper, we present a set of photometric observations in 15 colors of stars in the Landolt covered by the system range from 300 nm to 1000 nm. Visual magnitudes of the stars being studied in the field are from 10th to 20th mag. The observational methodology and the data reduction procedures are described. The relationships between the BATC intermediate-band system and the Landolt UBVRI broad band system are obtained. A catalogue of the photometry has been produced which contains the SEDs of 3613 stars. The electronic form of this catalogue can be accessed at the CDS via anonymous ftp to cdsarc.u-strasbg.fr.

Zhou, X; Ma, J; Xue, S; Wu, H; Chen, J; Zhu, J; Sun, W; Windhorst, R A; Zhou, Xu; Jiang, Zhaoji; Ma, Jun; Xue, Suijian; Wu, Hong; Chen, Jiansheng; Zhu, Jin; Sun, Weihsin; Windhorst, Rogier A.

2003-01-01T23:59:59.000Z

425

Oscillating red-giant stars in eccentric binary systems  

E-Print Network [OSTI]

The unparalleled photometric data obtained by NASA's Kepler Space Telescope has led to improved understanding of red-giant stars and binary stars. We discuss the characterization of known eccentric system, containing a solar-like oscillating red-giant primary component. We also report several new binary systems that are candidates for hosting an oscillating companion. A powerful approach to study binary stars is to combine asteroseimic techniques with light curve fitting. Seismology allows us to deduce the properties of red giants. In addition, by modeling the ellipsoidal modulations we can constrain the parameters of the binary system. An valuable independent source are ground-bases, high-resolution spectrographs.

Beck, P G; Vos, J; Kallinger, T; Garcia, R A; Mathur, S; Houmani, K

2014-01-01T23:59:59.000Z

426

Advanced Benchmarking: Benchmark Building Energy Use Quickly and Accurately Using EPA's ENERGY STAR Portfolio Manager  

Broader source: Energy.gov [DOE]

Advanced Benchmarking: Benchmark Building Energy Use Quickly and Accurately Using EPA's ENERGY STAR Portfolio Manager Webinar.

427

Comment submitted by Traulsen regarding the Energy Star Verification Testing Program  

Broader source: Energy.gov [DOE]

This document is a comment submitted by Traulsen regarding the Energy Star Verification Testing Program

428

Comment submitted by Consumers Union regarding the Energy Star Verification Testing Program  

Broader source: Energy.gov [DOE]

This document is a comment submitted by Consumers Union regarding the Energy Star Verification Testing Program

429

The Micro Craft iSTAR Micro Air Vehicle: Control System Design and Testing  

E-Print Network [OSTI]

-rotating propellers) benefits both reliability and cost. Figure 1: iSTAR Micro Air Vehicle The Micro Craft iSTAR VTOLThe Micro Craft iSTAR Micro Air Vehicle: Control System Design and Testing Larry Lipera i Abstract The iSTAR Micro Air Vehicle (MAV) is a unique 9-inch diameter ducted air vehicle weighing

Rotkowitz, Michael C.

430

Comment submitted by Whirlpool Corporation regarding the Energy Star Verification Testing Program  

Broader source: Energy.gov [DOE]

This document is a comment submitted by Whirlpool Corporation regarding the Energy Star Verification Testing Program

431

2006 Status Report Savings Estimates for the ENERGY STAR(R) Voluntary Labeling Program  

E-Print Network [OSTI]

Technology. August. AHAM. 2002. Excel Spreadsheet: "development process through AHAM. Energy Star wattages are

Webber, Carrie A.; Brown, Richard E.; Sanchez, Marla; Homan, Gregory K.

2006-01-01T23:59:59.000Z

432

2007 Status Report: Savings Estimates for the ENERGY STAR(R) VoluntaryLabeling Program  

E-Print Network [OSTI]

Technology. August. AHAM. 2002. Excel Spreadsheet: "development process through AHAM. Energy Star wattages are

Sanchez, Marla; Webber, Carrie A.; Brown, Richard E.; Homan, Gregory K.

2007-01-01T23:59:59.000Z

433

Institute of Astronomy, University of Vienna Delta Scuti Star Newsletter, Vol. 16?, 2001  

E-Print Network [OSTI]

;eld monitor and a star tracker. Recently, it has been proven beyond doubt, that solar-type stars.g. Australia and Spain. MONS is mainly a mission to study solar-type oscillations in nearby stars have solar-type stars as their main targets, both projects are aware of the possibilities of making

Frandsen, Søren

434

Beta Cephei stars in the ASAS-3 data. II. 103 new Beta Cephei stars and a discussion of low-frequency modes  

E-Print Network [OSTI]

We analysed ASAS-3 photometry of bright early-type stars with the goal of finding new Beta Cephei stars. We were particularly interested in stars that would be good for seismic analysis, i.e., stars that (i) have a large number of excited modes, (ii) show rotationally split modes, (iii) are components of eclipsing binary systems, (iv) have low-frequency modes, that is, are hybrid Beta Cephei/SPB stars. Our study was made with a homogeneous sample of over 4100 stars having MK spectral type B5 or earlier. For these stars, the ASAS-3 photometry was analysed by means of a Fourier periodogram. We have discovered 103 Beta Cephei stars, nearly doubling the number of previously known stars of this type. Among these stars, four are components of eclipsing binaries, seven have modes equidistant or nearly equidistant in frequency. In addition, we found five Beta Cephei stars that show low-frequency periodic variations, very likely due to pulsations. We therefore regard them as candidate hybrid Beta Cephei/SPB pulsators. All these stars are potentially very useful for seismic modeling. Moreover, we found Beta Cephei-type pulsations in three late O-type stars and fast period changes in one, HD 168050.

A. Pigulski; G. Pojma?ski

2007-11-15T23:59:59.000Z

435

ENERGY STAR Webinar: Zero Energy Ready Home Program | Department...  

Broader source: Energy.gov (indexed) [DOE]

home is as good as ENERGY STAR, the modest added "lift" to bring a home up to DOE's Zero Energy Ready specs unleashes a wave of powerful value messages. DOE Zero Energy Ready...

436

DOE's "Creating a Star on Earth" video highlights PPPL's magnetic...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

DOE's "Creating a Star on Earth" video highlights PPPL's magnetic fusion research March 5, 2014 Tweet Widget Google Plus One Share on Facebook A screenshot from the U.S. Department...

437

NineStar Connect- Residential Energy Efficient Equipment Rebate Program  

Broader source: Energy.gov [DOE]

Nine Star Connect (Greenfield and Maxwell, IN) offers residential customers an incentive to buy energy efficient air-source heat pumps, geothermal heat pumps. All heat pumps must meet minimum...

438

Multidimensional thermal structure of magnetized neutron star envelopes  

E-Print Network [OSTI]

Recently launched x-ray telescopes have discovered several candidate isolated neutron stars. The thermal radiation from these objects may potentially constrain our understanding of nuclear physics in a realm inaccessible to terrestrial experiments. To translate the observed fluxes from neutron stars into constraints, one needs precise calculations of the heat transfer through the thin insulating envelopes of neutron stars. We describe models of the thermal structure of the envelopes of neutron stars with magnetic fields up to 10^{14} G. Unlike earlier work, we infer the properties of envelope models in two dimensions and precisely account for the quantization of the electron phase space. Both dipole and uniformly magnetized envelopes are considered.

Jeremy S. Heyl; Lars Hernquist

1998-08-12T23:59:59.000Z

439

Entergy Texas- Energy Star Homes Program for Builders  

Broader source: Energy.gov [DOE]

Entergy Texas offers an incentive to builders in its service territory for the construction of Energy Star certified homes. The efficiency requirements can be met through a combination of...

440

Missouri Gas Energy (MGE)- Home Performance with ENERGY STAR  

Broader source: Energy.gov [DOE]

Missouri Gas Energy (MGE) offers rebates to its residential customers towards the cost of an ENERGY STAR Home Energy Assessment and a portion of the installed efficiency improvements. Home...

Note: This page contains sample records for the topic "waha lone star" 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

Pacific Power- Energy Star New Homes Program For Builders  

Broader source: Energy.gov [DOE]

Pacific Power provides an incentive for home builders in Washington to build energy efficient houses through the Energy Star New Homes Program. Rebates are available through this program for...

442

Equator Appliance: ENERGY STAR Referral (EZ 3720 CEE)  

Broader source: Energy.gov [DOE]

DOE referred the matter of Equator clothes washer model EZ 3720 CEE to the EPA for appropriate action after DOE testing showed that the model does not meet the ENERGY STAR specification.

443

IC 3418: STAR FORMATION IN A TURBULENT WAKE  

SciTech Connect (OSTI)

Galaxy Evolution Explorer observations of IC 3418, a low surface brightness galaxy in the Virgo Cluster, revealed a striking 17 kpc UV tail of bright knots and diffuse emission. H{alpha} imaging confirms that star formation is ongoing in the tail. IC 3418 was likely recently ram pressure stripped on its first pass through Virgo. We suggest that star formation is occurring in molecular clouds that formed in IC 3418's turbulent stripped wake. Tides and ram pressure stripping (RPS) of molecular clouds are both disfavored as tail formation mechanisms. The tail is similar to the few other observed star-forming tails, all of which likely formed during RPS. The tails' morphologies reflect the forces present during their formation and can be used to test for dynamical coupling between molecular and diffuse gas, thereby probing the origin of the star-forming molecular gas.

Hester, Janice A.; Neill, James D.; Wyder, Ted K.; Martin, D. Christopher [California Institute of Technology, Pasadena, CA 91125 (United States); Seibert, Mark; Madore, Barry F. [Observatories of the Carnegie Institute of Washington, Pasadena, CA 91101 (United States); Gil de Paz, Armando [Dpto. de Astrofisica, Universidad Computense de Madrid, Madrid 28040 (Spain); Schiminovich, David [Department of Astronomy, Columbia University, New York, NY 10027 (United States); Rich, R. Michael, E-mail: jhester@srl.caltech.ed [Department of Physics and Astronomy, Division of Astronomy and Astrophysics, University of California, Los Angeles, CA 90095 (United States)

2010-06-10T23:59:59.000Z

444

Phase conversion dissipation in multi-component compact stars  

E-Print Network [OSTI]

We propose a mechanism for the damping of density oscillations in multi-component compact stars. The mechanism is the periodic conversion between different phases, i.e. the movement of the interface between them, induced by pressure oscillations in the star. The damping grows nonlinearly with the amplitude of the oscillation. We study in detail the case of r-modes in a hybrid star with a sharp interface, and we find that this mechanism is powerful enough to saturate the r-mode at very low saturation amplitude, of order $10^{-10}$, and is therefore likely to be the dominant r-mode saturation mechanism in hybrid stars with a sharp interface.

Mark G. Alford; Sophia Han; Kai Schwenzer

2015-01-15T23:59:59.000Z

445

Energy Star Helps Manufacturers To Achieve High Energy Performance  

E-Print Network [OSTI]

From personal electronic devices to homes and office buildings, ENERGY STAR® is a recognized symbol of high quality energy performance which enables consumers, home buyers, and businesses to make informed energy decisions. Now, the U...

Dutrow, E.; Hicks, T.

446

Star-formation history of the universe and its drivers   

E-Print Network [OSTI]

Determining the cosmic star formation history of the Universe is fundamental for our understanding of galaxy formation and evolution. While surveys now suggest that the "epoch" of galaxy formation occurred more than 6 ...

Sobral, David Ricardo Serrano

2011-11-23T23:59:59.000Z

447

SUBSTRUCTURE IN BULK VELOCITIES OF MILKY WAY DISK STARS  

SciTech Connect (OSTI)

We find that Galactic disk stars near the anticenter exhibit velocity asymmetries in both the Galactocentric radial and vertical components across the midplane as well as azimuthally. These findings are based on Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) spectroscopic velocities for a sample of ?400, 000 F-type stars, combined with proper motions from the PPMXL catalog for which we have derived corrections to the zero points based in part on spectroscopically discovered galaxies and QSOs from LAMOST. In the region within 2 kpc outside the Sun's radius and ±2 kpc from the Galactic midplane, we show that stars above the plane exhibit net outward radial motions with downward vertical velocities, while stars below the plane have roughly the opposite behavior. We discuss this in the context of other recent findings, and conclude that we are likely seeing the signature of vertical disturbances to the disk due to an external perturbation.

Carlin, Jeffrey L.; DeLaunay, James; Newberg, Heidi Jo; Gole, Daniel; Grabowski, Kathleen [Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, Troy, NY 12180 (United States)] [Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, Troy, NY 12180 (United States); Deng, Licai; Liu, Chao; Luo, A-Li; Zhang, Haotong; Zhao, Gang; Zhao, Yongheng [Key Lab for Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)] [Key Lab for Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Jin, Ge [University of Science and Technology of China, Hefei 230026 (China)] [University of Science and Technology of China, Hefei 230026 (China); Liu, Xiaowei; Yuan, Haibo, E-mail: carlij@rpi.edu [Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China)] [Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China)

2013-11-01T23:59:59.000Z

448

australis stars soft: Topics by E-print Network  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Since none of the stars of these clusters has shown in the last years significant flux variations in the infrared, these two SGRs do not form bound binary systems with...

449

High energy gamma rays from old accreting neutron stars  

E-Print Network [OSTI]

We consider a magnetized neutron star with accretion from a companion star or a gas cloud around it, as a possible source of gamma rays with energy between $100$ $MeV$ and $10^{14}-10^{16}~eV$. The flow of the accreting plasma is terminated by a shock at the Alfv\\'en surface. Such a shock is the site for the acceleration of particles up to energies of $\\sim 10^{15}-10^{17}~eV$; gamma photons are produced in the inelastic $pp$ collisions between shock-accelerated particles and accreting matter. The model is applied to old neutron stars both isolated or in binary systems. The gamma ray flux above $100~MeV$ is not easily detectable, but we propose that gamma rays with very high energy could be used by Cherenkov experiments as a possible signature of isolated old neutron stars in dense clouds in our galaxy.

P. Blasi

1996-06-28T23:59:59.000Z

450

Home Performance with Energy Star High Efficiency Measure Incentive (HEMI)  

Broader source: Energy.gov [DOE]

The New York State Research and Development Authority (NYSERDA) offers an incentive for homeowners of 1-4 homes that participate in the Home Performance with Energy Star program. The program...

451

Data Management in the LoanSTAR Program  

E-Print Network [OSTI]

This paper discusses the complexity of managing building energy usage data for many buildings. The history and methodology of data collection at the Texas LoanSTAR Monitoring and Analysis Program, a large multimillion dollar project, is given...

Lopez, R. E.; Haberl, J. S.

452

ENERGY STAR® for SSL: Getting Ready for September 30  

Broader source: Energy.gov [DOE]

This June 26, 2008 webcast presented an overview of the DOE ENERGY STAR® criteria for solid-state luminaires, which became effective September 30, 2008. Richard Karney, DOE, discussed the...

453

Designing star trackers to meet micro-satellite requirements  

E-Print Network [OSTI]

Star trackers provide numerous advantages over other attitude sensors because of their ability to provide full, three-axis orientation information with high accuracy and flexibility to operate independently from other ...

Huffman, Kara M. (Kara Marie)

2006-01-01T23:59:59.000Z

454

Magnetism, rotation and accretion in Herbig Ae-Be stars  

E-Print Network [OSTI]

Studies of stellar magnetism at the pre-main sequence phase can provide important new insights into the detailed physics of the late stages of star formation, and into the observed properties of main sequence stars. This is especially true at intermediate stellar masses, where magnetic fields are strong and globally organised, and therefore most amenable to direct study. This talk reviews recent high-precision ESPaDOnS observations of pre-main sequence Herbig Ae-Be stars, which are yielding qualitatively new information about intermediate-mass stars: the origin and evolution of their magnetic fields, the role of magnetic fields in generating their spectroscopic activity and in mediating accretion in their late formative stages, and the factors influencing their rotational angular momentum.

Alecian, E; Catala, C; Folsom, C; Grunhut, J; Donati, J -F; Petit, P; Bagnulo, S; Bouret, T J -C; Landstreet, J D

2007-01-01T23:59:59.000Z

455

EU 'confident' of star power site By Jo Twist  

E-Print Network [OSTI]

from 2007 to 2013. Fusion powers stars and is seen as a cleaner approach to energy production than, and holds the record for fusion energy production. Based at Culham in Oxfordshire, it is a collaboration

456

Star Formation in Mergers and Interacting Galaxies: Gathering the Fuel  

E-Print Network [OSTI]

Selected results from recent studies of star formation in galaxies at different stages of interaction are reviewed. Recent results from the Spitzer Space Telescope are highlighted. Ideas on how large-scale driving of star formation in interacting galaxies might mesh with our understanding of star formation in isolated galaxies and small scale mechanisms within galaxies are considered. In particular, there is evidence that on small scales star formation is determined by the same thermal and turbulent processes in cool compressed clouds as in isolated galaxies. If so, this affirms the notion that the primary role of large-scale dynamics is to gather and compress the gas fuel. In gas-rich interactions this is generally done with increasing efficiency through the merger process.

Curtis Struck

2006-10-06T23:59:59.000Z

457

accreting neutron stars: Topics by E-print Network  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

a typical noise of 10-23 Hz-12. S. Bonazzola; E. Gourgoulhon 1996-06-20 13 Thermonuclear Burning on Rapidly Accreting Neutron Stars Astrophysics (arXiv) Summary: Neutron...

458

accreting neutron star: Topics by E-print Network  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

a typical noise of 10-23 Hz-12. S. Bonazzola; E. Gourgoulhon 1996-06-20 13 Thermonuclear Burning on Rapidly Accreting Neutron Stars Astrophysics (arXiv) Summary: Neutron...

459

accreted neutron star: Topics by E-print Network  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

a typical noise of 10-23 Hz-12. S. Bonazzola; E. Gourgoulhon 1996-06-20 13 Thermonuclear Burning on Rapidly Accreting Neutron Stars Astrophysics (arXiv) Summary: Neutron...

460

nderstanding the evolution of the first stars in the uni-  

E-Print Network [OSTI]

might have died as energetic thermonuclear explo- sions known as Pair-Instability Su- pernovae (PSNe and Astronomy Simulations of Thermonuclear Supernovae From Very Massive Stars Volume 27, Number 1 Also

Jovanovic, Mihailo

Note: This page contains sample records for the topic "waha lone star" 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.


461

Relativistic density functional theory for finite nuclei and neutron stars  

E-Print Network [OSTI]

The main goal of the present contribution is a pedagogical introduction to the fascinating world of neutron stars by relying on relativistic density functional theory. Density functional theory provides a powerful--and perhaps unique--framework for the calculation of both the properties of finite nuclei and neutron stars. Given the enormous densities that may be reached in the core of neutron stars, it is essential that such theoretical framework incorporates from the outset the basic principles of Lorentz covariance and special relativity. After a brief historical perspective, we present the necessary details required to compute the equation of state of dense, neutron-rich matter. As the equation of state is all that is needed to compute the structure of neutron stars, we discuss how nuclear physics--particularly certain kind of laboratory experiments--can provide significant constrains on the behavior of neutron-rich matter.

Piekarewicz, J

2015-01-01T23:59:59.000Z

462

Duke Energy (Electric)- Energy Star Homes Rate Discount Program  

Broader source: Energy.gov [DOE]

Duke Energy encourages residential customers to buy energy-efficient homes through the utility's [http://www.energystar.gov/index.cfm?c=new_homes.hm_index Energy Star Homes Program], which awards a...

463

Isospin asymmetric nuclear matter and properties of axisymmetric neutron stars  

E-Print Network [OSTI]

Pure hadronic compact stars, above a limiting value ($\\approx$1.6 M$_\\odot$) of their gravitational masses, to which predictions of most of other equations of state (EoSs) are restricted, can be reached from the equation of state (EoS) obtained using DDM3Y effective interaction. This effective interaction is found to be quite successful in providing unified description of elastic and inelastic scattering, various radioactivities and nuclear matter properties. We present a systematic study of the properties of pure hadronic compact stars. The $\\beta$-equilibrated neutron star matter using this EoS with a thin crust is able to describe highly-massive compact stars, such as PSR B1516+02B with a mass M=1.94$^{+0.17}_{-0.19}$ M$_\\odot$ and PSR J0751+1807 with a mass M=2.1$\\pm$0.2 M$_\\odot$ to a 1$\\sigma$ confidence level.

Partha Roy Chowdhury; Abhijit Bhattacharyya; D. N. Basu

2011-01-06T23:59:59.000Z

464

Seismic evolution of low/intermediate mass PMS stars  

E-Print Network [OSTI]

This article presents a study of the evolution of the internal structure and seismic properties expected for low/intermediate mass Pre-Main Sequence (PMS) stars. Seismic and non-seismic properties of PMS stars were analysed. This was done using 0.8 to 4.4M$_\\odot$ stellar models at stages ranging from the end of the Hayashi track up to the Zero-Age Main-Sequence (ZAMS). This research concludes that, for intermediate-mass stars (M$>$1.3M$_\\odot$), diagrams comparing the effective temperature ($T_{eff}$) against the small separation can provide an alternative to Christensen-Dalsgaard (C-D) diagrams. The impact of the metal abundance of intermediate mass stars (2.5-4.4M$_\\odot$) has over their seismic properties is also evaluated.

F. J. G. Pinheiro

2007-12-05T23:59:59.000Z

465

australis star forming: Topics by E-print Network  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

star forming regions. Our optical photometry is combined with available near- and mid-infrared photometry to identify very low-mass candidate members in these dark clouds. In our...

466

Isovector potential of $?$ in nuclei and neutron star matter  

E-Print Network [OSTI]

We determine the coupling constants of $\\Sigma$ hyperon with mesons in relativistic mean field (RMF) models using $\\Sigma^-$ atomic shift data and examine the effects of $\\Sigma$ on the neutron star maximum mass. We find that we need to reduce the vector-isovector meson coupling with $\\Sigma$ ($g_{\\rho\\Sigma}$) from the value constrained by the SU(3)v symmetry in order to explain the $\\Sigma^-$ atomic shifts for light symmetric and heavy asymmetric nuclei simultaneously. With the atomic shift fit value of $g_{\\rho\\Sigma}$, $\\Sigma^-$ can emerge in neutron star matter overcoming the repulsive isoscalar potential for $\\Sigma$ hyperons. Admixture of $\\Sigma^-$ in neutron stars is found to reduce the neutron star maximum mass slightly.

K. Tsubakihara; A. Ohnishi; T. Harada

2014-02-05T23:59:59.000Z

467

South River EMC- Energy Star Homes Rebate Program  

Broader source: Energy.gov [DOE]

South River EMC offers incentives to home buyers and builders who purchase or construct Energy Star certified single-family site built homes, manufactured homes, and multi-family dwellings. Energy...

468

Kansas City Power and Light- Home Performance with ENERGY STAR  

Broader source: Energy.gov [DOE]

Kansas City Power and Light (KCP&L) offers rebates to residential customers towards the cost of an ENERGY STAR Home Energy Assessment and a portion of the installed efficiency improvements....

469

ENERGY STAR for Homes - Building America Top Innovation | Department...  

Energy Savers [EERE]

more than 1.3 million ENERGY STAR certified homes have delivered 23 billion in energy cost savings and avoided 210 million tons of green-house emissions. Strong...

470

Stars as thermonuclear reactors: their fuels and ashes  

E-Print Network [OSTI]

Atomic nuclei are transformed into each other in the cosmos by nuclear reactions inside stars: -- the process of nucleosynthesis. The basic concepts of determining nuclear reaction rates inside stars and how they manage to burn their fuel so slowly most of the time are discussed. Thermonuclear reactions involving protons in the hydrostatic burning of hydrogen in stars are discussed first. This is followed by triple alpha reactions in the helium burning stage and the issues of survival of carbon and oxygen in red giant stars connected with nuclear structure of oxygen and neon. Advanced stages of nuclear burning in quiescent reactions involving carbon, neon, oxygen and silicon are discussed. The role of neutron induced reactions in nucleosynthesis beyond iron is discussed briefly, as also the experimental detection of neutrinos from SN 1987A which confirmed broadly the ideas concerning gravitational collapse leading to a supernova.

A. Ray

2004-05-28T23:59:59.000Z

471

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

472

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

2002-03-20T23:59:59.000Z

473

Friedrich: ENERGY STAR Referral (SM18M30)  

Broader source: Energy.gov [DOE]

DOE referred the matter of Friedrich room air conditioner model SM18M30 to the EPA for appropriate action after DOE testing showed that the model does not meet the ENERGY STAR specification.

474

ENERGY STAR Honors a Few of Its Founders  

Office of Energy Efficiency and Renewable Energy (EERE)

The American Council for an Energy Efficient Economy celebrated visionaries and leaders in energy efficiency recently, including two of the Energy Department’s own for their key roles in founding and implementing the ENERGY STAR® program.

475

The chemical abundances of the Ap star HD94660  

SciTech Connect (OSTI)

In this work I present the determination of chemical abundances of the Ap star HD94660, a possible rapid oscillating star. As all the magnetic chemically peculiar objects, it presents CNO underabundance and overabundance of iron peak elements of ?100 times and of rare earths up to 4 dex with respect to the Sun. The determination was based on the conversion of the observed equivalent widths into abundances simultaneously to the determination of effective temperature and gravity. Since the Balmer lines of early type stars are very sensitive to the surface gravity while the flux distribution is sensitive to the effective temperature, I have adopted an iterative procedure to match the H{sub ?} line profile and the observed UV-Vis-NIR magnitudes of HD94660 looking for a consistency between the metallicity of the atmosphere model and the derived abundances. From my spectroscopic analysis, this star belongs to the no-rapid oscillating class.

Giarrusso, M. [Università di Catania, Dipartimento di Fisica e Astronomia, Sezione Astrofisica, Via S. Sofia 78, 95123 Catania (Italy); INAF - Osservatorio Astrofisico di Catania, via S. Sofia 78, 95123 Catania (Italy); INFN - Laboratori Nazionali del Sud (Italy)

2014-05-09T23:59:59.000Z

476

Building dwarf galaxies out of merged young star clusters  

E-Print Network [OSTI]

Young star clusters in interacting galaxies are often found in groups or clusters of star clusters containing up to 100 single clusters. In our project we study the future fate of these clusters of star clusters. We find that the star clusters merge on time scales of a few dynamical crossing times of the super-cluster. The resulting merger object has similarities with observed dwarf ellipticals (dE). Furthermore, if destructive processes like tidal heating, dynamical friction or interaction with disc or bulge of the parent galaxy are taken into account our merger objects may evolve into objects resembling dwarf spheroidal galaxies (dSph), without the need of a high dark matter content.

M. Fellhauer

2001-06-22T23:59:59.000Z

477

North Star Refrigerator: Proposed Penalty (2013-CE-5355)  

Broader source: Energy.gov [DOE]

DOE alleged in a Notice of Proposed Civil Penalty that North Star Refrigerator Co., Inc. failed to certify a variety of walk-in cooler or freezer components as compliant with the applicable energy conservation standards.

478

The viscoelastic properties of linear-star blends  

E-Print Network [OSTI]

In order to understand the nature of polydispersity and characterize the effect of branching architecture, the model blend of linear and star polymer, which is the simplest branched polymer, is contrived. In this blend system, chain dynamics...

Lee, Jung Hun

2000-01-01T23:59:59.000Z

479

Anisotropic Compact Stars in $f(T)$ Gravity  

E-Print Network [OSTI]

This paper deals with the theoretical modeling of anisotropic compact stars in the framework of $f(T)$ theory of gravity, where $T$ is torsion scalar. To this end, we have used the exact solutions of Krori and Barua metric to a static spherically symmetric metric. The unknown constants involved in the Krori and Barua metric have been specified by using the masses and radii of compact stars 4$U$1820-30, Her X-1, SAX J 1808-3658. The physical properties of these stars have been analyzed in the framework of $f(T)$ theory. In this setting, we have checked the anisotropic behavior, regularity conditions, stability and surface redshift of the compact stars.

Abbas, G; Zubair, M

2015-01-01T23:59:59.000Z

480

Anisotropic Compact Stars in $f(G)$ Gravity  

E-Print Network [OSTI]

This paper is devoted to study the possibility of forming anisotropic compact stars in"modified Gauss-Bonnet, namely called as $f(G)$ theory of gravity which is one of the strong candidates, responsible for the accelerated expansion of the universe. For this purpose, we have used analytical solution of Krori and Barua metric to the Einstein field equations with anisotropic form of matter and power law model of $f(G)$ gravity. To determine the unknown constants in Krori and Barua metric, we have used the masses and radii of compact stars, 4$U$1820-30, Her X-1, SAX J 1808-3658. The physical behavior of these stars have been analyzed with the observational data. In this setting, we have checked all the regularity conditions and stability the compact stars 4$U$1820-30, Her X-1, SAX J 1808-3658.

G. Abbas; D. Momeni; M. Aamir Ali; R. Myrzakulov; S. Qaisar

2014-12-26T23:59:59.000Z

Note: This page contains sample records for the topic "waha lone star" 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.


481

Anisotropic Compact Stars in $f(R)$ Gravity  

E-Print Network [OSTI]

In this paper we have investigated the possibility of forming of anisotropic compact stars in $f(R)$ gravity, one of the competent candidates of dark energy. To this end, we have applied the analytical solution of Krori and Barua metric to a static spherically symmetric spacetime in $f(R)$ gravity. The unknown constants in Krori and Barua metric have been determined by using masses and radii of class of compact stars like 4$U$1820-30, Her X-1, SAX J 1808-3658. The properties of these stars have been analyzes in detail. Furthermore, we have checked the regularity conditions, energy conditions, anisotropic behavior, stability and surface redshift of the compact stars 4$U$1820-30, Her X-1, SAX J 1808-3658.

M. Zubair; G. Abbas

2015-02-06T23:59:59.000Z

482

Anisotropic Compact Stars in $f(T)$ Gravity  

E-Print Network [OSTI]

This paper deals with the theoretical modeling of anisotropic compact stars in the framework of $f(T)$ theory of gravity, where $T$ is torsion scalar. To this end, we have used the exact solutions of Krori and Barua metric to a static spherically symmetric metric. The unknown constants involved in the Krori and Barua metric have been specified by using the masses and radii of compact stars 4$U$1820-30, Her X-1, SAX J 1808-3658. The physical properties of these stars have been analyzed in the framework of $f(T)$ theory. In this setting, we have checked the anisotropic behavior, regularity conditions, stability and surface redshift of the compact stars.

G. Abbas; Afshan Kanwal; M. Zubair

2015-01-22T23:59:59.000Z

483

Anisotropic Compact Stars in $f(G)$ Gravity  

E-Print Network [OSTI]

This paper is devoted to study the possibility of forming anisotropic compact stars in"modified Gauss-Bonnet, namely called as $f(G)$ theory of gravity which is one of the strong candidates, responsible for the accelerated expansion of the universe. For this purpose, we have used analytical solution of Krori and Barua metric to the Einstein field equations with anisotropic form of matter and power law model of $f(G)$ gravity. To determine the unknown constants in Krori and Barua metric, we have used the masses and radii of compact stars, 4$U$1820-30, Her X-1, SAX J 1808-3658. The physical behavior of these stars have been analyzed with the observational data. In this setting, we have checked all the regularity conditions and stability the compact stars 4$U$1820-30, Her X-1, SAX J 1808-3658.

Abbas, G; Ali, M Aamir; Myrzakulov, R; Qaisar, S

2015-01-01T23:59:59.000Z

484

VEE-0040- In the Matter of Western Star Propane, Inc.  

Broader source: Energy.gov [DOE]

On February 18, 1997, Western Star Propane, Inc. (Western) filed an Application for Exception with the Office of Hearings and Appeals (OHA) of the Department of Energy (DOE). In its application,...

485

Reading Municipal Light Department- Residential ENERGY STAR Appliance Rebate Program  

Broader source: Energy.gov [DOE]

Reading Municipal Light Department (RMLD) offers rebates to residential customers who install Energy Star appliances in eligible homes. The offer is limited to one rebate per appliance or a maximum...

486

Resonant Oscillations and Tidal Heating in Coalescing Binary Neutron Stars  

E-Print Network [OSTI]

Tidal interaction in a coalescing neutron star binary can resonantly excite the g-mode oscillations of the neutron star when the frequency of the tidal driving force equals the intrinsic g-mode frequencies. We study the g-mode oscillations of cold neutron stars using recent microscopic nuclear equations of state, where we determine self-consistently the sound speed and Brunt-V\\"ais\\"al\\"a frequency in the nuclear liquid core. The properties of the g-modes associated with the stable stratification of the core depend sensitively on the pressure-density relation as well as the symmetry energy of the dense nuclear matter. The frequencies of the first ten g-modes lie approximately in the range of $10-100$ Hz. Resonant excitations of these g-modes during the last few minutes of the binary coalescence result in energy transfer and angular momentum transfer from the binary orbit to the neutron star. The angular momentum transfer is possible because a dynamical tidal lag develops even in the absence of fluid viscosity. However, since the coupling between the g-mode and the tidal potential is rather weak, the amount of energy transfer during a resonance and the induced orbital phase error are very small. Resonant excitations of the g-modes play an important role in tidal heating of binary neutron stars. Without the resonances, viscous dissipation is effective only when the stars are close to contact. The resonant oscillations result in dissipation at much larger orbital separation. The actual amount of tidal heating depends on the viscosity of the neutron star. Using the microscopic viscosity, we find that the binary neutron stars are heated to a temperature $\\sim 10^8$ K before they come into contact.

Dong Lai

1994-04-25T23:59:59.000Z

487

Extent of pollution in planet-bearing stars  

E-Print Network [OSTI]

(abridged) Search for planets around main-sequence (MS) stars more massive than the Sun is hindered by their hot and rapidly spinning atmospheres. This obstacle has been sidestepped by radial-velocity surveys of those stars on their post-MS evolutionary track (G sub-giant and giant stars). Preliminary observational findings suggest a deficiency of short-period hot Jupiters around the observed post MS stars, although the total fraction of them with known planets appears to increase with their mass. Here we consider the possibility that some very close- in gas giants or a population of rocky planets may have either undergone orbital decay or been engulfed by the expanding envelope of their intermediate-mass host stars. If such events occur during or shortly after those stars' main sequence evolution when their convection zone remains relatively shallow, their surface metallicity can be significantly enhanced by the consumption of one or more gas giants. We show that stars with enriched veneer and lower-metallicity interior follow slightly modified evolution tracks as those with the same high surface and interior metallicity. As an example, we consider HD149026, a marginal post MS 1.3 Msun star. We suggest that its observed high (nearly twice solar) metallicity may be confined to the surface layer as a consequence of pollution by the accretion of either a planet similar to its known 2.7-day-period Saturn-mass planet, which has a 70 Mearth compact core, or a population of smaller mass planets with a comparable total amount of heavy elements. It is shown that an enhancement in surface metallicity leads to a reduction in effective temperature, in increase in radius and a net decrease in luminosity. The effects of such an enhancement are not negligible in the determinations of the planet's radius based on the transit light curves.

S. -L. Li; D. N. C. Lin; X. -W. Liu

2008-02-17T23:59:59.000Z

488

Can Population III Stars at High Redshifts produce GRB's?  

E-Print Network [OSTI]

Gamma ray bursts are the most luminous physical phenomena in the universe, consisting of flashes of gamma rays that last from seconds to hours. There have been attempts to observe gamma ray bursts, for example, from population III stars of about 500 solar mass at high redshifts. Here we argue that collapse of such high mass stars does not lead to gamma ray burst as their core collapse temperatures are not sufficient to produce gamma rays, leading to GRBs.

C. Sivaram; Kenath Arun

2010-08-24T23:59:59.000Z

489

Short Gamma-Ray Bursts from Binary Neutron Star Mergers  

E-Print Network [OSTI]

We present the results from new relativistic hydrodynamic simulations of binary neutron star mergers using realistic non-zero temperature equations of state. We vary several unknown parameters in the system such as the neutron star (NS) masses, their spins and the nuclear equation of state. The results are then investigated with special focus on the post-merger torus-remnant system. Observational implications on the Gamma-ray burst (GRB) energetics are discussed and compared with recent observations.

Roland Oechslin; Thomas Janka

2006-04-27T23:59:59.000Z

490

The chemistry of high-mass star formation  

E-Print Network [OSTI]

This paper reviews the chemistry of star-forming regions, with an emphasis on the formation of high-mass stars. We first outline the basic molecular processes in dense clouds, their implementation in chemical models, and techniques to measure molecular abundances. Then, recent observational, theoretical and laboratory developments are reviewed on the subjects of hot molecular cores, cosmic-ray ionization, depletion and deuteration, and oxygen chemistry. The paper concludes with a summary of outstanding problems and future opportunities.

Floris F. S. van der Tak

2005-06-07T23:59:59.000Z

491

The Early Evolution of Massive Stars: Radio Recombination Line Spectra  

E-Print Network [OSTI]

Velocity shifts and differential broadening of radio recombination lines are used to estimate the densities and velocities of the ionized gas in several hypercompact and ultracompact HII regions. These small HII regions are thought to be at their earliest evolutionary phase and associated with the youngest massive stars. The observations suggest that these HII regions are characterized by high densities, supersonic flows and steep density gradients, consistent with accretion and outflows that would be associated with the formation of massive stars.

Eric Keto; Qizhou Zhang; Stanley Kurtz

2007-11-15T23:59:59.000Z

492

Measuring the Balmer Jump and Effective Gravity in FGK Stars  

E-Print Network [OSTI]

It is difficult to accurately measure the effective gravity (log g) in late-type stars using broadband (eg. UBV or SDSS) or intermediate-band (uvby) photometric systems, especially when the stars can cover a range of metallicities and reddenings. However, simple spectroscopic observational and data reduction techniques can yield accurate values for log g through comparison of the Balmer jumps of low-resolution spectra with recent grids of synthetic flux spectra.

Bessell, Michael S

2007-01-01T23:59:59.000Z

493

UV Star Formation Rates in the Local Universe  

E-Print Network [OSTI]

We measure star formation rates of ~50,000 optically-selected galaxies in the local universe (z~0.1), spanning a range from gas-rich dwarfs to massive ellipticals. We obtain dust-corrected SFRs by fitting the GALEX (UV) and SDSS (optical) photometry to a library of population synthesis models that include dust attenuation. For star-forming galaxies, our UV-based SFRs compare remarkably well with those derived from SDSS H alpha. Deviations from perfect agreement between these two methods are due to differences in the dust attenuation estimates. In contrast to H alpha, UV provides reliable SFRs for galaxies with weak or no H alpha emission, and where H alpha is contaminated with an emission from an AGN. We use full-SED SFRs to calibrate a simple prescription that uses GALEX UV magnitudes to produce good SFRs for normal star-forming galaxies. The specific SFR is considered as a function of stellar mass for (1) star-forming galaxies with no AGN, (2) those hosting an AGN, and for (3) galaxies without H alpha emission. We find that the three have distinct star formation histories, with AGN lying intermediate between the star-forming and the quiescent galaxies. Normal star forming galaxies (without an AGN) lie on a relatively narrow linear sequence. Remarkably, galaxies hosting a strong AGN appear to represent the massive continuation of this sequence. Weak AGN, while also massive, have lower SFR, sometimes extending to the realm of quiescent galaxies. We propose an evolutionary sequence for massive galaxies that smoothly connects normal star-forming galaxies to quiescent (red sequence) galaxies via strong and weak AGN. We confirm that some galaxies with no H alpha emission show signs of SF in the UV. We derive a UV-based cosmic SFR density at z=0.1 with smaller total error than previous measurements (abridged).

Samir Salim; R. Michael Rich; Stéphane Charlot; Jarle Brinchmann; Benjamin D. Johnson; David Schiminovich; Mark Seibert; Ryan Mallery; Timothy M. Heckman; Karl Forster; Peter G. Friedman; D. Christopher Martin; Patrick Morrissey; Susan G. Neff; Todd Small; Ted K. Wyder; Luciana Bianchi; Jose Donas; Young-Wook Lee; Barry F. Madore; Bruno Milliard; Alex S. Szalay; Barry Y. Welsh; Sukyoung K. Yi

2007-05-07T23:59:59.000Z

494

Lithium depletion and the rotational history of exoplanet host stars  

E-Print Network [OSTI]

Israelian et al. (2004) reported that exoplanet host stars are lithium depleted compared to solar-type stars without detected massive planets, a result recently confirmed by Gonzalez (2008). We investigate whether enhanced lithium depletion in exoplanet host stars may result from their rotational history. We have developed rotational evolution models for slow and fast solar-type rotators from the pre-main sequence (PMS) to the age of the Sun and compare them to the distribution of rotational periods observed for solar-type stars between 1 Myr and 5 Gyr. We show that slow rotators develop a high degree of differential rotation between the radiative core and the convective envelope, while fast rotators evolve with little core-envelope decoupling. We suggest that strong differential rotation at the base of the convective envelope is responsible for enhanced lithium depletion in slow rotators. We conclude that lithium-depleted exoplanet host stars were slow rotators on the zero-age main sequence (ZAMS) and argue that slow rotation results from a long lasting star-disk interaction during the PMS. Altogether, this suggests that long-lived disks (> 5 Myr) may be a necessary condition for massive planet formation/migration.

Jerome Bouvier

2008-09-03T23:59:59.000Z

495

The Star Formation History of the Small Magellanic Cloud  

E-Print Network [OSTI]

We present the spatially-resolved star formation and chemical enrichment history of the Small Magellanic Cloud (SMC) across the entire central $4-degree x 4.5-degree area of the main body, based on UBVI photometry from our Magellanic Clouds Photometric Survey. We find that 1) approximately 50% of the stars that ever formed in the SMC formed prior to 8.4 Gyr ago (z >1.2 for WMAP cosmology), 2) the SMC formed relatively few stars between 8.4 and 3 Gyr ago, 3) there was a rise in the mean star formation rate during the most recent 3 Gyr punctuated by "bursts" at ages of 2.5, 0.4, and 0.06 Gyr, 4) the bursts at 2.5 and 0.4 Gyr are temporally coincident with past perigalactic passages of the SMC with the Milky Way, 5) there is preliminary evidence for a large-scale annular structure in the 2.5 Gyr burst, and 6) the chemical enrichment history derived from our analysis is in agreement with the age-metallicity relation of the SMC's star clusters. Consistent interpretation of the data required an ad hoc correction of 0.1-0.2 mag to the B-V colors of 25% of the stars; the cause of this anomaly is unknown, but we show that it does not strongly influence our results.

J. Harris; D. Zaritsky

2003-12-03T23:59:59.000Z

496

Wind Circulation in Selected Rotating Magnetic Early-B Stars  

E-Print Network [OSTI]

The rotating magnetic B stars have oblique dipolar magnetic fields and often anomalous helium and metallic compositions. These stars develop co-rotating torus-shaped clouds by channelling winds from their magnetic poles to an anchored planar disk over the magnetic equator. The line absorptions from the cloud can be studied as the complex rotates and periodically occults the star. We describe an analysis of the clouds of four stars (HD184927, beta Cep, sigma Ori E, and HR6684). From line synthesis models, we find that the metallic compositions are spatially uniform over the stars' surfaces. Next, using the Hubeny CIRCUS code, we demonstate that periodic UV continuum fluxes can be explained by the absorption of low-excitation lines. The analysis also quantifies the cloud temperatures, densities, and turbulences, which appear to increase inward toward the stars. The temperatures range from about 12,000K for the weak Fe lines up to temperatures of 33,000K for N V absorptions, which is in excess of temperatures expected from radiative equilibrium. The spectroscopic hallmark of this stellar class is the presence of strong C IV and N V resonance line absorptions at occultation phases and of redshifted emissions at magnetic pole-on phases. The emissions have characteristics which seem most compatible with the generation of high-energy shocks at the wind-cloud interface, as predicted by Babel.

Myron A. Smith; Detlef Groote

2001-04-03T23:59:59.000Z

497

On the star formation history of IZw 18  

E-Print Network [OSTI]

It has been suggested that a continuous low star formation rate has been the dominant regime in IZw 18 and in dwarf galaxies for the lifetime of these objects (Legrand et al. 1999). Here, we discuss and model various star-forming histories for IZw 18. Particularly, we show that if the metallicity observed in IZw 18 results from starburst events only, the observed colors constrain the fraction of the metals ejected from the galaxy to be less than 50-70 %. We demonstrate that the continuous star formation scenario reproduces the observed parameters of IZw 18. A continuous star formation rate (SFR) of about 10E-4 Msol/yr during 14 Gyr reproduces precisely the observed abundances. This SFR is comparable with the lowest SFR observed in low surface brightness galaxies (van Zee et al. 1997). Generalized to all galaxies, the low continuous SFR scenario accounts for various facts: the presence of star formation in quiescent dwarfs and LSBG, the metallicity increase with time in the most underabundant DLA systems, and the metal content extrapolations to the outskirts of spiral galaxies. Also the apparent absence of galaxies with a metallicity lower than IZw 18, the apparent absence of HI clouds without optical counterparts, and the homogeneity of abundances in dwarfs galaxies are natural outcomes of the scenario. This implies that, even if starbursts are strong and important events in the life of galaxies, their more subdued but continuous star formation regime cannot be ignored when accounting for their chemical evolution.

F. Legrand

1999-12-06T23:59:59.000Z

498

Magnetism and rotation in Herbig Ae/Be stars  

E-Print Network [OSTI]

Among the main sequence intermediate mass A and B stars, around 5% host large-scale organized magnetic fields. Most of these stars are very slow rotators compared to their non-magnetic counterparts, and show photospheric abundance anomalies. They are referred to as the Ap/Bp stars. One of the greatest challenges, today is to understand the origin of their magnetic field and their slow rotation. The favoured hypothesis is a fossil origin of the magnetic field, in which the magnetic fields of Ap/Bp stars are relics of those which existed in the parental molecular clouds during the formation. This implies that the magnetic field must survive all the initial phases of the stellar evolution and especially the pre-main sequence (PMS) phase. This is consistent with the general belief that magnetic braking occurs during the PMS phase, which sheds angular momentum and slows the rotation of these stars. In this context, we proceeded with a survey of a sample of around 50 PMS Herbig Ae/Be stars, using the new spectropol...

Alecian, E; Catala, C; Folsom, C; Grunhut, J; Donati, J -F; Petit, P; Bagnulo, S; Böhm, T; Bouret, J -C; Landstreet, J D

2007-01-01T23:59:59.000Z

499

Final Fate of Subcritical Evolutions of Boson Stars  

E-Print Network [OSTI]

We present results from a study of Type I critical phenomena in the dynamics of general relativistic boson stars in spherical symmetry. The boson stars are modelled with a minimally coupled, massive complex field (with no explicit self-interaction), and are driven to the threshold of black hole formation via their gravitational interaction with an initially imploding pulse of massless scalar field. Using a distinct coordinate system, we reproduce previous results [1,2], including the scaling of the lifetime of near-critical configurations, as well as the fact that such configurations are well described as perturbed, one-mode-unstable boson stars. In addition, we make a detailed study of the long-time evolution of marginally subcritical configurations. Contrary to previous claims [1,2], we find that the end state in such cases does not involve dispersal of the bulk of the boson star field to large radial distances, but instead can be generically described by a stable boson star executing large amplitude oscillations. Furthermore we show that these oscillations can be largely identified as excitations of the fundamental mode associated with the final boson star, as computed in perturbation theory.

Chi Wai Lai; Matthew W. Choptuik

2007-09-04T23:59:59.000Z

500

ON STAR FORMATION RATES AND STAR FORMATION HISTORIES OF GALAXIES OUT TO z {approx} 3  

SciTech Connect (OSTI)

We compare multi-wavelength star formation rate (SFR) indicators out to z {approx} 3 in the GOODS-South field. Our analysis uniquely combines U to 8 {mu}m photometry from FIREWORKS, MIPS 24 {mu}m and PACS 70, 100, and 160 {mu}m photometry from the PEP, and H{alpha} spectroscopy from the SINS survey. We describe a set of conversions that lead to a continuity across SFR indicators. A luminosity-independent conversion from 24 {mu}m to total infrared luminosity yields estimates of L{sub IR} that are in the median consistent with the L{sub IR} derived from PACS photometry, albeit with significant scatter. Dust correction methods perform well at low-to-intermediate levels of star formation. They fail to recover the total amount of star formation in systems with large SFR{sub IR}/SFR{sub UV} ratios, typically occuring at the highest SFRs (SFR{sub UV+IR} {approx}> 100 M{sub sun} yr{sup -1}) and redshifts (z {approx}> 2.5) probed. Finally, we confirm that H{alpha}-based SFRs at 1.5 < z < 2.6 are consistent with SFR{sub SED} and SFR{sub UV+IR} provided extra attenuation toward H II regions is taken into account (A{sub V,neb} = A{sub V,continuum}/0.44). With the cross-calibrated SFR indicators in hand, we perform a consistency check on the star formation histories inferred from spectral energy distribution (SED) modeling. We compare the observed SFR-M relations and mass functions at a range of redshifts to equivalents that are computed by evolving lower redshift galaxies backward in time. We find evidence for underestimated stellar ages when no stringent constraints on formation epoch are applied in SED modeling. We demonstrate how resolved SED modeling, or alternatively deep UV data, may help to overcome this bias. The age bias is most severe for galaxies with young stellar populations and reduces toward older systems. Finally, our analysis suggests that SFHs typically vary on timescales that are long (at least several 100 Myr) compared to the galaxies' dynamical time.

Wuyts, Stijn; Foerster Schreiber, Natascha M.; Lutz, Dieter; Nordon, Raanan; Berta, Stefano; Genzel, Reinhard; Magnelli, Benjamin; Poglitsch, Albrecht [Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany); Altieri, Bruno [Herschel Science Centre, ESAC, Villanueva de la Canada, 28691 Madrid (Spain); Andreani, Paola [ESO, Karl-Schwarzschild-Str. 2, D-85748 Garching (Germany); Aussel, Herve; Daddi, Emanuele; Elbaz, David [Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot, IRFU/Service d'Astrophysique, Bat.709, CEA-Saclay, 91191 Gif-sur-Yvette Cedex (France); Bongiovanni, Angel; Cepa, Jordi; Garcia, Ana Perez [Instituto de Astrofisica de Canarias, 38205 La Laguna (Spain); Cimatti, Andrea [Departamento di Astronomia, Universita di Bologna, via Ranzani 1, 40127 Bologna (Italy); Koekemoer, Anton M. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Maiolino, Roberto [INAF, Osservatorio Astronomico di Roma, via di Frascati 33, 00040 Monte Porzio Catone (Italy); McGrath, Elizabeth J. [University of California Observatories/Lick Observatory, University of California, Santa Cruz, CA 95064 (United States)

2011-09-01T23:59:59.000Z