INTEGRAL/IBIS 7-year All-Sky Hard X-Ray Survey

Abstract

This paper is the second in a series devoted to the hard X-ray (17−60 keV) whole sky survey performed by the INTEGRAL observatory over seven years. Here we present a catalog of detected sources that includes 521 objects, 449 of which exceed a 5σ detection threshold on the time-averaged map of the sky, and 53 were detected in various subsamples of exposures. Among the identified sources with known and suspected nature, 262 are Galactic (101 low-mass X-ray binaries, 94 high-mass X-ray binaries, 37 cataclysmic variables, and 30 of other types) and 221 are extragalactic, including 217 active galactic nuclei (AGNs) and 4 galaxy clusters. The extragalactic (|b| > 5 • ) and Galactic (|b| < 5 • ) persistently detected source samples have high identification completeness (respectively ∼96% and ∼93%) and are valuable for population studies.

Unveiling the nature ofINTEGRALobjects through optical spectroscopy

“…In a similar way to Papers I−VII, and this time using the two largest and most recently available IBIS surveys Krivonos et al 2010), we selected unidentified or unclassified hard X-ray sources that contain, within the IBIS 90% confidence level error box, a single bright soft X-ray object detected either in the ROSAT all-sky surveys (Voges et al 1999(Voges et al , 2000, or with Swift/XRT (from Baumgartner et al 2008;Landi et al 2009Landi et al , 2010Mescheryakov et al 2009;Krivonos et al 2009;Coe et al 2009;Kniazev et al 2010;McBride et al 2010, andin some cases independently -from the XRT archive 3 ), or in the XMM-Newton Slew Survey (Saxton et al 2008), or with Chandra ). This approach was proven by Stephen et al (2006) to be very effective in associating, with a high degree of probability, IBIS sources with a softer X-ray counterpart and in turn drastically reducing their positional error circles to a few arcsec in radius, thus shrinking the search area by a factor of ∼10 4 .…”

“…For the source naming in Table 1, we simply adopted the names as they appear in the relevant catalogs Krivonos 2010) or papers (Bozzo et al 2009;Coe et al 2010;McBride et al 2010), and the "IGR" alias when available. However, we note that for one of the hard X-ray objects selected by means of cross-correlation with soft X-ray catalogs, i.e., 1RXS J191928.5−295808, we chose to use its ROSAT name (thus associated with its soft X-ray emission) rather than the denomination reported in the 4th IBIS Survey (PKS 1916−300;Bird et al 2010) because the latter refers to a radio source that is slightly but significantly offset from the optical and soft X-ray positions of the possible counterpart to this INTEGRAL hard X-ray object.…”

“…The X-ray luminosities listed in this table for the various objects were computed using the fluxes reported in Table 1). Voges et al (1999Voges et al ( , 2000, Bird et al (2010), Cusumano et al (2010), Krivonos et al (2010), and Landi et al (2010).…”

“…Table 3 collects the relevant optical spectral information about these 6 sources, along with their main parameters inferred from the available X-ray and optical data. X-ray luminosities in Table 3 were calculated using the fluxes in Saxton et al (2008), Bozzo et al (2009), Rodriguez et al (2009, Krivonos et al (2010), andMcBride et al (2010). In this table, we also report the results of our R-band photometry of the counterpart of IGR J16287−5021, described in Sect.…”

“…In these tables, X-ray luminosities were computed from the fluxes reported in Voges et al (1999Voges et al ( , 2000, Saxton et al (2008), Krivonos et al (2009, Cusumano et al (2010), Krivonos et al (2010), Landi et al (2010), Rodriguez et al (2010), and Tueller et al (2010).…”