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Description
The ongoing XMM-Newton Slew Survey (XSS) provides coverage of a significant fraction of the sky in a broad X-ray bandpass. Although shallow by contemporary standards, in the "classical" 2-10 keV band of X-ray astronomy the XSS provides significantly better sensitivity than any currently available all-sky survey. The authors investigate the source content of the XSS, focusing on detections in the hard 2-10 keV band down to a very low threshold (>= 4 counts net of background). At the faint end, the survey reaches a flux sensitivity of roughly 3 x 10<sup>-12</sup> erg/cm<sup>2</sup>/s (2-10 keV). The starting point was a sample of 487 sources detected in the XSS (up to and including release XMMSL1d2) at high galactic latitude in the hard band. Through cross-correlation with published source catalogs from surveys spanning the electromagnetic spectrum from radio through to gamma-rays, they find that 45% of the sources have likely identifications with normal/active galaxies. A further 18% are associated with other classes of X-ray object (nearby coronally active stars, accreting binaries, clusters of galaxies), leaving 37% of the XSS sources with no current identification. The authors go on to define an XSS extragalactic sample comprised of 219 galaxies and active galaxies selected in the XSS hard band. They investigate the properties of this extragalactic sample including its X-ray log N - log S distribution, and it is this sample that is contained in this table. The authors find that, in the low-count limit, the XSS is, as expected, strongly affected by Eddington bias. There is also a very strong bias in the XSS against the detection of extended sources, most notably clusters of galaxies. A significant fraction of the detections at and around the low-count limit may be spurious. Nevertheless, it is possible to use the XSS to extract a reasonably robust sample of extragalactic sources, excluding galaxy clusters. The differential log N - log S relation of these extragalactic sources matches very well to the HEAO-1 A2 all-sky survey measurements at bright fluxes and to the 2XMM source counts at the faint end. The substantial sky coverage afforded by the XSS makes this survey a valuable resource for studying X-ray bright source samples, including those selected specifically in the hard 2 - 10 keV band. This table was created by the HEASARC in December 2012, based on the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/548/A99">CDS Catalog J/A+A/548/A99</a> file tablea1.dat. This is a service provided by NASA HEASARC .
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