The Palermo Swift-BAT hard X-ray catalogue^*

II. Results after 39 months of sky survey

G. Cusumano¹, V. La Parola¹, A. Segreto¹, V. Mangano¹, C. Ferrigno^1,2,3, A. Maselli¹, P. Romano¹, T. Mineo¹, B. Sbarufatti¹, S. Campana⁴, G. Chincarini^5,4, P. Giommi⁶, N. Masetti⁷, A. Moretti⁴ and G. Tagliaferri⁴

¹ INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica di Palermo, via U. La Malfa 153, 90146 Palermo, Italy e-mail: cusumano@ifc.inaf.it
² Institut für Astronomie und Astrophysik Tübingen (IAAT), Germany
³ ISDC Data Centre for Astrophysics, Chemin d'Écogia 16, 1290 Versoix, Switzerland
⁴ INAF – Osservatorio Astronomico di Brera, via Bianchi 46, 23807 Merate, Italy
⁵ Università degli studi di Milano-Bicocca, Dipartimento di Fisica, Piazza delle Scienze 3, 20126 Milan, Italy
⁶ ASI Science Data Center, via Galileo Galilei, 00044 Frascati, Italy
⁷ INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna, via Gobetti 101, 40129 Bologna, Italy

Received: 17 October 2008
Accepted: 23 June 2009

Abstract

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  10^-11 erg cm^-2 s^-1  and 50% of the sky down to a flux limit of 1.8  10^-11 erg cm^-2 s^-1 in the 14-150 keV band. We derived a catalogue of 754 identified sources, of which % are extragalactic, % are Galactic objects, and % are already known X-ray or gamma ray emitters, whose nature has yet to be determined. The integrated flux of the extragalactic sample is  of the cosmic X-ray background in the 14-150 keV range.