The Palermo Swift-BAT hard X-ray catalogue II. Results after 39 months of sky survey

Aims. We present the Palermo Swift-BAT hard X-ray catalogue obtained from the analysis of data acquired during the first 39 months of the Swift mission. Methods. We developed a dedicated software to perform the data reduction, mosaicking, and source detection of the BAT survey data. We analyzed the BAT dataset in three energy bands (14-150 keV, 14-30 keV, 14-70 keV), obtaining a list of 962 detections above a significance threshold of 4.8 standard deviations. The identification of the source counterparts was pursued using three strategies: cross-correlation with published hard X-ray catalogues, analysis of field observations of soft X-ray instruments, and cross-correlation with SIMBAD databases. Results. The survey covers 90% of the sky down to a flux limit of 2.5 x 10(-11) erg cm(-2) s(-1) and 50% of the sky down to a flux limit of 1.8 x 10(-11) erg cm(-2) s(-1) in the 14-150 keV band. We derived a catalogue of 754 identified sources, of which similar to 69% are extragalactic, similar to 27% are Galactic objects, and similar to 4% are already known X-ray or gamma ray emitters, whose nature has yet to be determined. The integrated flux of the extragalactic sample is similar to 1% of the cosmic X-ray background in the 14-150 keV range.