NED Abstract 
Copyright by European Southern Observatory (ESO).
Reproduced by permission

2010A&A...524A..64C

The Palermo Swift-BAT hard X-ray catalogue. III. Results after 54 months of
sky survey

Cusumano, G.; La Parola, V.; Segreto, A.; Ferrigno, C.; Maselli, A.;
Sbarufatti, B.; Romano, P.; Chincarini, G.; Giommi, P.; Masetti, N.;
Moretti, A.; Parisi, P.; Tagliaferri, G.

Abstract.  Aims: We present the Second Palermo Swift-BAT hard X-ray
catalogue obtained by analysing data acquired in the first 54 months of
the Swift mission.  Methods: Using our software dedicated to the analysis
of data from coded mask telescopes, we analysed the BAT survey data in
three energy bands (15-30 keV, 15-70 keV, 15-150 keV), obtaining a list of
1256 detections above a significance threshold of 4.8 standard deviations.
The identification of the source counterparts is pursued using two
strategies: the analysis of field observations of soft X-ray instruments
and cross-correlation of our catalogue with source databases.  Results:
The survey covers 50% of the sky to a 15-150 keV flux limit of 1.0x10^-11^
erg cm^-2^ s^-1^ and 9.2x10^-12^ erg cm^-2^ s^-1^ for |b| < 10^degree^ and
|b| > 10^degree^, respectively. The Second Palermo Swift-BAT hard X-ray
catalogue includes 1079 (~86%) hard X-ray sources with an associated
counterpart (26 with a double association and 2 with a triple association)
and 177 BAT excesses (~14%) that still lack a counterpart. The
distribution of the BAT sources among the different object classes
consists of ~19% Galactic sources, ~57% extragalactic sources, and ~10%
sources with a counterpart at softer energies whose nature has not yet
been determined. About half of the BAT associated sources lack a
counterpart in the ROSAT catalogues. This suggests that either moderate or
strong absorption may be preventing their detection in the ROSAT energy
band. The comparison of our BAT catalogue with the Fermi Large Area
Telescope First Source Catalogue identifies 59 BAT/Fermi correspondences:
48 blazars, 3 Seyfert galaxies, 1 interacting galaxy, 3 high mass X-ray
binaries, and 4 pulsars/supernova remnants. This small number of
correspondences indicates that different populations make the sky shine in
these two different energy bands.

Key words: catalogs, surveys, X-rays: general