THE 70 MONTH SWIFT -BAT ALL-SKY HARD X-RAY SURVEY

Abstract

We present the catalog of sources detected in the first 22 months of data from the hard X-ray survey (14-195 keV) conducted with the Burst Alert Telescope (BAT) coded mask imager on the Swift satellite. The catalog contains 461 sources detected above the 4.8σ level with BAT. High angular resolution X-ray data for every source from Swift-XRT or archival data have allowed associations to be made with known counterparts in other wavelength bands for over 97% of the detections, including the discovery of ∼30 galaxies previously unknown as active galactic nuclei and several new Galactic sources. A total of 266 of the sources are associated with Seyfert galaxies (median redshift z ∼ 0.03) or blazars, with the majority of the remaining sources associated with X-ray binaries in our Galaxy. This ongoing survey is the first uniform all-sky hard X-ray survey since HEAO-1 in 1977. Since the publication of the nine-month BAT survey we have increased the number of energy channels from four to eight and have substantially increased the number of sources with accurate average spectra. The BAT 22 month catalog is the product of the most sensitive all-sky survey in the hard X-ray band, with a detection sensitivity (4.8σ) of 2.2 × 10 −11 erg cm −2 s −1 (1 mCrab) over most of the sky in the 14-195 keV band.

The Third Swift Burst Alert Telescope Gamma-Ray Burst Catalog

“…The figure shows a clear correlation of the minimum fluxes of the detected GRBs and the burst durations. This correlation of the energy flux and T 90 is very similar to BAT sensitivity (as a function of exposure time) derived in Baumgartner et al (2013) (Equation (9)), despite that in Baumgartner et al (2013) the sensitivity is derived for non-GRB sources with Crab-like spectra, and for a signal-to-noise ratio of s 5 (instead of the ∼6.5 to 7σ threshold used for GRB detections). However, note that this plot includes only the GRBs with "acceptable spectral fits" (as defined by criteria described in Section 3.1).…”

“…To perform further search of pre-burst or extended GRB emissions beyond the period of the event data, we use the results of the 104 month survey analysis, which is an extension of the previously published 70 month survey data analyses (Baumgartner et al 2013). The survey process performs standard survey analysis using the script batsurvey, 38 and generates mask-weighted, cleaned images for each observations in eight energy bands (14-20, 20-24, 24-35, 35-50, 50-75, 75-100, 100-150, 150-195 keV).…”

“…Ideally, one would require the observation time of each image to be identical to have a fair comparison of the signal-to-noise ratio in each image. However, because the survey process (Baumgartner et al 2013) only produces one image for each observation (i.e., using the "SNAPSHOT" option in batsurvey 38 ), our estimation can only based on these images with different exposure times. To produce survey images with finer time bins in each observation (i.e., using the "DPH" option in batsurvey 38 ), one would need to re-process all survey data and the process will take ∼ months to years to finish, and hence would be beyond the scope of this paper.…”

The e-ASTROGAM mission

“…INTEGRAL/SPI data for the 1809 keV 26 Al line suggest that on the global, Galactic scale, superbubbles are key structures in the transport of fresh ejecta towards new star forming regions [86,87]. With its huge increase in sensitivity, e-ASTROGAM will provide a detailed view of the morphology of this emission, with high precision measurements of the line flux from many regions of the Galaxy.…”

“…Thus, e-ASTROGAM will observe the 26 Al radioactivity from dozens of nearby (∼kpc) stellar objects and associations. In particular, it will measure precisely the amount of 26 Al ejected by the Wolf-Rayet star WR11 in the γ 2 -Velorum binary system (expected line flux of ∼10 −5 ph cm −2 s −1 ), thus providing a unique calibration of the 26 Al production during the Wolf-Rayet phase of a massive star. e-ASTROGAM has also the capability of detecting 26 Al emission from the LMC (expected line flux of ∼10 −6 ph cm −2 s −1 ), thus providing new insight into stellar nucleosynthesis outside the Milky Way.…”