The 22-Month Swift-BAT All-Sky Hard X-ray Survey

TL;DR

This paper presents the 22-month Swift-BAT all-sky hard X-ray survey catalog, detecting 461 sources, including new AGN and Galactic sources, with high sensitivity and improved spectral data, marking the most sensitive survey in this band to date.

Contribution

The paper provides the first uniform all-sky hard X-ray survey since 1977, with increased energy channels and improved source spectra, expanding the catalog of detected sources significantly.

Findings

Detected 461 sources above 4.8 sigma

Discovered ~30 new AGN and several Galactic sources

Achieved the most sensitive all-sky hard X-ray survey to date

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 BAT coded mask imager on the \swift satellite. The catalog contains 461 sources detected above the 4.8 sigma 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 AGN 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 9-month BAT survey we have increased the number of energy channels from 4 to 8 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 (4.8 sigma) of 2.2e-11 erg/cm2/s (1 mCrab) over most of the sky in the 14--195 keV band.