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