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Title: The Swift Gamma-Ray Burst Explorer: The Latest Results

Abstract

The Swift GRB Explorer mission is designed to discover {approx} 100 new gamma-ray bursts each year, and immediately (within tens of seconds) to start simultaneous X-ray, optical and ultraviolet observations of the GRB afterglow. Since its launch on 20 November 2004, it has already collected an impressive database of gamma ray bursts (reaching more sensitive limits than BATSE); uniform X-ray/UV/optical monitoring of afterglows (with a dedicated weatherless observatory with broad multi-wavelength imaging capability); and rapid followup by other observatories (utilizing a continuous ground link with burst alerts and data posted immediately to the GCN)

Authors:
 [1]
  1. Dept. of Astronomy and Astrophysics, Penn State University, University Park, PA 16802 (United States)
Publication Date:
OSTI Identifier:
20719688
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 801; Journal Issue: 1; Conference: Conference on astrophysical sources of high energy particles and radiation, Torun (Poland), 20-24 Jun 2005; Other Information: DOI: 10.1063/1.2141830; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; AFTERGLOW; COSMIC GAMMA BURSTS; COSMIC GAMMA SOURCES; ULTRAVIOLET RADIATION; WAVELENGTHS

Citation Formats

Nousek, John A. The Swift Gamma-Ray Burst Explorer: The Latest Results. United States: N. p., 2005. Web. doi:10.1063/1.2141830.
Nousek, John A. The Swift Gamma-Ray Burst Explorer: The Latest Results. United States. doi:10.1063/1.2141830.
Nousek, John A. Tue . "The Swift Gamma-Ray Burst Explorer: The Latest Results". United States. doi:10.1063/1.2141830.
@article{osti_20719688,
title = {The Swift Gamma-Ray Burst Explorer: The Latest Results},
author = {Nousek, John A.},
abstractNote = {The Swift GRB Explorer mission is designed to discover {approx} 100 new gamma-ray bursts each year, and immediately (within tens of seconds) to start simultaneous X-ray, optical and ultraviolet observations of the GRB afterglow. Since its launch on 20 November 2004, it has already collected an impressive database of gamma ray bursts (reaching more sensitive limits than BATSE); uniform X-ray/UV/optical monitoring of afterglows (with a dedicated weatherless observatory with broad multi-wavelength imaging capability); and rapid followup by other observatories (utilizing a continuous ground link with burst alerts and data posted immediately to the GCN)},
doi = {10.1063/1.2141830},
journal = {AIP Conference Proceedings},
number = 1,
volume = 801,
place = {United States},
year = {Tue Nov 22 00:00:00 EST 2005},
month = {Tue Nov 22 00:00:00 EST 2005}
}
  • The Swift Gamma-Ray Burst Explorer has revolutionized the study of these remarkable high-energy explosions. We summarize the technical developments which lead to the creation of the Swift mission, and outline the highlights of the first three years, and the prospects ahead.
  • Since its launch on 20 November 2004, the Swift mission is detecting {approx}100 new gamma-ray bursts (GRBs) each year, and immediately (within tens of seconds) starting simultaneous X-ray and UV/optical observations of the afterglow. It has already collected am impressive database of bursts, including prompt emission to higher sensitivity than BATSE, uniform monitoring of afterglows, and rapid follow-up by other observatories notified through the GCN.
  • Compact binary system mergers are expected to generate gravitational radiation detectable by ground-based interferometers. A subset of these, the merger of a neutron star with another neutron star or a black hole, are also the most popular model for the production of short gamma-ray bursts (GRBs). The Swift Burst Alert Telescope (BAT) and the Fermi Gamma-ray Burst Monitor (GBM) trigger on short GRBs (SGRBs) at rates that reflect their relative sky exposures, with the BAT detecting 10 per year compared to about 45 for GBM. We examine the SGRB populations detected by Swift BAT and Fermi GBM. We find thatmore » the Swift BAT triggers on weaker SGRBs than Fermi GBM, providing they occur close to the center of the BAT field of view, and that the Fermi GBM SGRB detection threshold remains flatter across its field of view. Overall, these effects combine to give the instruments the same average sensitivity, and account for the SGRBs that trigger one instrument but not the other. We do not find any evidence that the BAT and GBM are detecting significantly different populations of SGRBs. Both instruments can detect untriggered SGRBs using ground searches seeded with time and position. The detection of SGRBs below the on-board triggering sensitivities of Swift BAT and Fermi GBM increases the possibility of detecting and localizing the electromagnetic counterparts of gravitational wave (GW) events seen by the new generation of GW detectors.« less
  • After about 18 yr of steadily spinning down, the accretion-powered pulsar 4U 1626-67 experienced a new torque reversal at the beginning of 2008. For the present study, we have used all available Fermi/Gamma-ray Burst Monitor data since its launch in 2008 June 11 and over 5 yr of hard X-ray Swift/Burst Alert Telescope observations (starting from 2004 October up to the present time). From 2004 up to the end of 2007 the spin-down rate averaged at a mean rate of approxnu-dot=-4.8 x 10{sup -13} Hz s{sup -1} until the torque reversal reported here. This second detected torque reversal was centeredmore » near MJD 54500 (2008 February 4) and it lasted approximately 150 days. During the reversal, the source also underwent an increase in flux by a fraction of approx2.5. Since then it has been following a steady spin-up at a mean rate of approxnu-dot=-4 x 10{sup -13} Hz s{sup -1}. We present a detailed long-term timing analysis of this source and a long-term spectral hardness ratio study in order to see whether there are spectral changes around this new observed torque reversal.« less
  • We present the second Swift Burst Alert Telescope (BAT) catalog of gamma-ray bursts (GRBs), which contains 476 bursts detected by the BAT between 2004 December 19 and 2009 December 21. This catalog (hereafter the BAT2 catalog) presents burst trigger time, location, 90% error radius, duration, fluence, peak flux, time-averaged spectral parameters, and time-resolved spectral parameters measured by the BAT. In the correlation study of various observed parameters extracted from the BAT prompt emission data, we distinguish among long-duration GRBs (L-GRBs), short-duration GRBs (S-GRBs), and short-duration GRBs with extended emission (S-GRBs with E.E.) to investigate differences in the prompt emission properties.more » The fraction of L-GRBs, S-GRBs, and S-GRBs with E.E. in the catalog are 89%, 8%, and 2%, respectively. We compare the BAT prompt emission properties with the BATSE, BeppoSAX, and HETE-2 GRB samples. We also correlate the observed prompt emission properties with the redshifts for the GRBs with known redshift. The BAT T{sub 90} and T{sub 50} durations peak at 70 s and 30 s, respectively. We confirm that the spectra of the BAT S-GRBs are generally harder than those of the L-GRBs. The time-averaged spectra of the BAT S-GRBs with E.E. are similar to those of the L-GRBs. Whereas, the spectra of the initial short spikes of the S-GRBs with E.E. are similar to those of the S-GRBs. We show that the BAT GRB samples are significantly softer than the BATSE bright GRBs and that the time-averaged E {sup obs}{sub peak} of the BAT GRBs peaks at 80 keV, which is significantly lower energy than those of the BATSE sample, which peak at 320 keV. The time-averaged spectral properties of the BAT GRB sample are similar to those of the HETE-2 GRB samples. By time-resolved spectral analysis, we find that only 10% of the BAT observed photon indices are outside the allowed region of the synchrotron shock model. We see no obvious observed trend in the BAT T{sub 90} and the observed spectra with redshifts. The T{sub 90} and T{sub 50} distributions measured at the 140-220 keV band in the GRB rest frame from the BAT known redshift GRBs peak at 19 s and 8 s, respectively. We also provide an update on the status of the on-orbit BAT calibrations.« less