Abstract
We present the 1SXPS (Swift-XRT Point Source) catalog of 151,524 X-ray point-sources detected by the Swift-XRT in 8 years of operation. The catalog covers 1905 square degrees distributed approximately uniformly on the sky. We analyze the data in two ways. First we consider all observations individually, for which we have a typical sensitivity of ~3e-13 erg/cm2/s (0.3--10 keV). Then we co-add all data covering the same location on the sky: these images have a typical sensitivity of ~9e-14 erg/cm2/s (0.3--10 keV). Our sky coverage is nearly 2.5 times that of 3XMM-DR4, although the catalog is a factor of ~1.5 less sensitive. The median position error is 5.5" (90% confidence), including systematics. Our source detection method improves on that used in previous XRT catalogs and we report >68,000 new X-ray sources. The goals and observing strategy of the Swift satellite allow us to probe source variability on multiple timescales, and we find ~30,000 variable objects in our catalog. For every source we give positions, fluxes, time series (in four energy bands and two hardness ratios), estimates of the spectral properties, spectra and spectral fits for the brightest sources, and variability probabilities in multiple energy bands and timescales.
Highlights
Serendipitous X-ray source catalogs have been produced for most X-ray satellites since the Einstein mission (e.g., Gioia et al 1990; Voges et al 1999; Ueda et al 2005; Watson et al 2009; Evans et al 2010) and have contributed much to our understanding of the X-ray sky
There is a small number of locations on the sky (4% of those covered by our catalog) where overlapping observations exist that extend beyond the 1000 × 1000 pixel (=39.9 × 39.3) range of the sky coordinates in the X-ray Telescope (XRT) event files and could not be covered by a single stacked image
We identified all sources in the Rosat PSPC and 2XMMi-DR3 catalogs with fluxes above this limit, and selected for manual screening all fields in our catalog that lay within 28 –82 of those sources
Summary
Serendipitous X-ray source catalogs have been produced for most X-ray satellites since the Einstein mission (e.g., Gioia et al 1990; Voges et al 1999; Ueda et al 2005; Watson et al 2009; Evans et al 2010) and have contributed much to our understanding of the X-ray sky. The Swift satellite (Gehrels et al 2004) has several unique features which mean that a serendipitous source catalog produced from its X-ray Telescope (XRT; Burrows et al 2005) can make a distinctive contribution to this field, in the area of source variability. To make this catalog we have analyzed Swift-XRT data from the first 8 yr of operations, covering 13,065 distinct locations (giving a coverage of 1905 deg2), of which 81% were observed at least twice.
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