The 54-month Palermo BAT-survey catalogue

Using our software dedicated to the analysis of data from coded mask telescopes, we analysed the BAT survey data in three energy bands (15-30keV, 15-70keV, 15-150keV), 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.

The survey covers 50% of the sky to a 15-150keV flux limit of 1.0x10^-11^erg/cm2/s and 9.2x10^-12^erg/cm2/s for |b|<10 and |b|>10, 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.