The Burst Alert Telescope (BAT) on the Swift gamma-ray burst mission serves as the GRB trigger for Swift as well as a sensitive imaging telescope for the energy range of 15-150 keV. All BAT data ...products will be available to the astronomical community along with a complete set of analysis tools. Gamma-ray burst data products include rapid discovery messages delivered immediately via the GRB Coordinates Network, and event-by-event data from which light curves and spectra of the burst are generated. During nominal operations, the instrument provides accumulated survey histograms with 5-minute time sampling and appropriate energy resolution. These survey accumulations are analyzed in a pipeline to detect new sources and derive light curves of known sources. The 5-minute surveys will also be combined to produce the BAT all sky hard X-ray survey. In addition, the instrument accumulates high time resolution light curves of the brightest BAT sources in multiple energy bands, which are merged into a source light curve database on the ground. The BAT science data products and analysis tools will be described in this paper.
We report the simultaneous observations of the prompt emission in the gamma-ray and hard X-ray bands by the Swift BAT and the Konus-Wind instruments of the short-hard burst, GRB 060313. The ...observations reveal multiple peaks in both the gamma-ray and hard X-ray bands suggesting a highly variable outflow from the central explosion. We also describe the early-time observations of the X-ray and UV/optical afterglows by the Swift XRT and UVOT instruments. The combination of the X-ray and UV/optical observations provides the most comprehensive light curves to date of a short-hard burst at such an early epoch. The afterglows exhibit complex structure with different decay indices and flaring. This behavior can be explained by the combination of a structured jet, radiative loss of energy, and decreasing microphysics parameters occurring in a circumburst medium with densities varying by a factor of approximately two on a length scale of 10 super(17) cm. These density variations are normally associated with the environment of a massive star and inhomogeneities in its windy medium. However, the mean density of the observed medium (n610 super(4) cm super(3)) is much less than that expected for a massive star. Although the collapse of a massive star as the origin of GRB 060313 is unlikely, the merger of a compact binary also poses problems for explaining the behavior of this burst. Two possible suggestions for explaining this scenario are that some short bursts may arise from a mechanism that does not invoke the conventional compact binary model, or that soft late-time central engine activity is producing UV/optical but no X-ray flaring.
THEORY predicts1 that radioactive 26 A1 (which has a half-life of 0.72 Myr) is released into the interstellar medium by nova and supernova explosions, from the winds of massive stars in the ...Wolf-Rayet phase, and from less-massive giant stars in very late stages of the asymptotic giant branch phase. Observations of 1,809-keV -ray emission line from 26 A1 can therefore be used as a tracer of Galactic nucleosynthesis during the past million years2,3 . The irregularity of the emission in the plane of the Galaxy4-7 suggests that the dominant sources are likely to be massive stars and supernovae; the other predicted sources are older, and therefore expected to be distributed more uniformly. Here we report the detection of the 1,809-keV emission line from the direction of the Galactic Centre, and we show that the line width is approximately three times that expected8,9 from the effect of Doppler broadening due to Galactic rotation. The high velocities inferred from the line width favour an origin of the 26 A1 in supernovae or Wolf-Rayet stars. Moreover, the fact that the 26 A1 has maintained such high velocities is difficult to reconcile with our current understanding of the propagation of material in the interstellar medium.
Swift discovered the high-redshift GRB 050319 with the Burst Alert Telescope (BAT) and began observing with its narrow-field instruments only 225 s after the burst onset. The afterglow X-ray emission ...was monitored by the XRT up to 28 days after the burst. The light curve shows a decay with three different phases, each characterized by a distinct slope: an initial steep decay with a power-law index of 65.5, a second phase characterized by a flat decay slope of 60.54, and a third phase with a decay slope of 61.14. During the first phase the spectral energy distribution is softer than in the following two phases, and the photon index is consistent with the GRB prompt spectrum. The extrapolation of the BAT light curve to the XRT band suggests that the initial fast-decaying phase of the XRT afterglow might be the low-energy tail of the prompt emission. The second break in the afterglow light curve occurs about 27,000 s after the burst. The spectral energy distribution before and after the second break does not change, and it can be tentatively interpreted as a jet break or the end of a delayed or continuous energy injection phase.
The properties of 32K CdZnTe (
4
×
4
mm
2
large, 2
mm thick) detectors have been studied in the pre-flight calibration of the Burst Alert Telescope (BAT) on-board the Swift Gamma-ray Burst Explorer ...(scheduled for launch in November 2004). In order to understand the energy response of the BAT CdZnTe array, we first quantify the mobility-lifetime (
μ
τ
) products of carriers in individual CdZnTe detectors, which produce a position dependency in the charge induction efficiency and results in a low-energy tail in the energy spectrum. Based on a new method utilizing
57Co spectra obtained at different bias voltages, the
μ
τ
for electrons ranges from
5.0
×
10
-
4
to
1.0
×
10
-
2
cm
2
V
-
1
while the
μ
τ
for holes ranges from
1.3
×
10
-
5
to
1.8
×
10
-
4
cm
2
V
-
1
. We find that this wide distribution of
μ
τ
products explains the large diversity in spectral shapes between CdZnTe detectors well. We also find that the variation of
μ
τ
products can be attributed to the difference of crystal ingots or manufacturing harness. We utilize the 32K sets of extracted
μ
τ
products to develop a spectral model of the detector. In combination with Monte Carlo simulations, we can construct a spectral model for any photon energy or any incident angle.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The gamma-ray burst (GRB) rate is essential for revealing the connection between GRBs, supernovae and stellar evolution. Additionally, the GRB rate at high redshift provides a strong probe of star ...formation history in the early universe. While hundreds of GRBs are observed by Swift, it remains difficult to determine the intrinsic GRB rate due to the complex trigger algorithm of Swift. Current studies of the GRB rate usually approximate the Swift trigger algorithm by a single detection threshold. However, unlike the previously flown GRB instruments, Swift has over 500 trigger criteria based on photon count rate and additional image threshold for localization. To investigate possible systematic biases and explore the intrinsic GRB properties, we develop a program that is capable of simulating all the rate trigger criteria and mimicking the image threshold. Our simulations show that adopting the complex trigger algorithm of Swift increases the detection rate of dim bursts. As a result, our simulations suggest bursts need to be dimmer than previously expected to avoid over-producing the number of detections and to match with Swift observations. Moreover, our results indicate that these dim bursts are more likely to be high redshift events than low-luminosity GRBs. This would imply an even higher cosmic GRB rate at large redshifts than previous expectations based on star-formation rate measurements, unless other factors, such as the luminosity evolution, are taken into account. The GRB rate from our best result gives a total number of 4571^{+829}_{-1584} GRBs per year that are beamed toward us in the whole universe. SPECIAL NOTE (2015.05.16): This new version incorporates an erratum. All the GRB rate normalizations (\(R_{\rm GRB}(z=0)\)) should be a factor of 2 smaller than previously reported. Please refer to the Appendix for more details. We sincerely apologize for the mistake.
We present a catalog of hard X-ray sources detected in the first 105 months of observations with the Burst Alert Telescope (BAT) coded mask imager on board the Swift observatory. The 105 month ...Swift-BAT survey is a uniform hard X-ray all-sky survey with a sensitivity of \(8.40\times 10^{-12}\ {\rm erg\ s^{-1}\ cm^{-2}}\) over 90% of the sky and \(7.24\times 10^{-12}\ {\rm erg\ s^{-1}\ cm^{-2}}\) over 50% of the sky in the 14-195 keV band. The Swift-BAT 105 month catalog provides 1632 (422 new detections) hard X-ray sources in the 14-195 keV band above the 4.8{\sigma} significance level. Adding to the previously known hard X-ray sources, 34% (144/422) of the new detections are identified as Seyfert AGN in nearby galaxies (z<0.2). The majority of the remaining identified sources are X-ray binaries (7%, 31) and blazars/BL Lac objects (10%, 43). As part of this new edition of the Swift-BAT catalog, we release eight-channel spectra and monthly sampled light curves for each object in the online journal and at the Swift-BAT 105 month Web site.
The Swift/Burst Alert Telescope detected the first burst from 1E 1841--045 in 2010 May with intermittent burst activity recorded through at least 2011 July. Here we present Swift and Fermi/Gamma-ray ...Burst Monitor observations of this burst activity and search for correlated changes to the persistent X-ray emission of the source. The T 90 durations of the bursts range between 18 and 140 ms, comparable to other magnetar burst durations, while the energy released in each burst ranges between (0.8-25) X 1038 erg, which is on the low side of soft gamma repeater bursts. We find that the bursting activity did not have a significant effect on the persistent flux level of the source. We argue that the mechanism leading to this sporadic burst activity in 1E 1841--045 might not involve large-scale restructuring (either crustal or magnetospheric) as seen in other magnetar sources.
We present the newly developed broadband transient monitor using the Swift Burst Alert Telescope (BAT) and the MAXI Gas Slit Camera (GSC) data. Our broadband transient monitor monitors high energy ...transient sources from 2 keV to 200 keV in seven energy bands by combining the BAT (15-200 keV) and the GSC (2-20 keV) data. Currently, the daily and the 90-minute (one orbit) averaged light curves are available for 106 high energy transient sources. Our broadband transient monitor is available to the public through our web server, http://yoshidalab.mydns.jp/bat_gsc_trans_mon/, for a wider use by the community. We discuss the daily sensitivity of our monitor and possible future improvements to our pipeline.
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