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.
Highlights
Surveys of the whole sky that are complete to a well-defined threshold provide a basis for statistical population studies but are a vehicle for the discovery of new phenomena
We find a weak hard X-ray source whose position is consistent with V2491 Cyg in data taken before its eruption as Nova Cyg 2008b. (see Ibarra et al (2009), ATel 1478) Transient; later seen with Integral (ATel 967) X-ray Telescope (XRT) data show that this source is the same as 1RXS J231930.9+261525, reported and identified as a cataclysmic variables (CVs) of subtype AM Her in ATel 1309
A blank indicates that the object is Galacatic, and a ? indicates that the object has an unknown redshift. h The luminosity is computed from the flux and redshift in this table, with units of log[erg s−1] in the 14–195 keV band
Summary
Surveys of the whole sky that are complete to a well-defined threshold provide a basis for statistical population studies but are a vehicle for the discovery of new phenomena. The RXTE all-sky slew survey (Revnivtsev et al 2004) covers much of the sky in the 3–20 keV band and detects 294 sources, but the coverage is not uniform or complete and the sensitivity is weighted to lower energies such that the BAT and RXTE sources are not the same. The resultant survey provides the most uniform hard X-ray survey to date and achieves a sensitivity sufficient to detect very large numbers of sources, both Galactic and extragalactic. Markwardt et al (2005) have published the results from the first three months of BAT data, and Tueller et al (2008) have published a survey of sources seen in the first nine months of Swift observations, concentrating on the 103 AGNs seen at Galactic latitudes greater than 15◦. We present here a catalog of all sources detected in the first 22 months of operations (2005 December 15–2006 October 27), increasing the number of AGNs to 266 and including all other sources seen across the entire sky
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