The seven year Swift-XRT point source catalog (1SWXRT)

The Swift satellite is a multi-wavelength observatory specifically designed for gamma-ray burst (GRB) astronomy that is operational since 2004. Swift is also a very flexible multi-purpose facility that supports a wide range of scientific fields such as active galactic nuclei, supernovae, cataclysmic variables, Galactic transients, active stars and comets. The Swift X-ray Telescope (XRT) has collected more than 150 Ms of observations in its first seven years of operations. Aims. The purpose of this work is to present to the scientific community the list of all the X-ray point sources detected in XRT imaging data taken in photon counting mode during the first seven years of Swift operations. All these point-like sources, excluding the GRB, will be stored in a catalog publicly available (1SWXRT). Methods. We considered all the XRT observations with exposure time longer than 500 s taken in the period 2005−2011. Data were reduced and analyzed with standard techniques and a list of detected sources for each observation was produced. A careful visual inspection was performed to remove extended, spurious and piled-up sources. Finally, positions, count rates, fluxes, and the corresponding uncertainties were computed. Results. We have analyzed more than 35 000 XRT fields, with exposures ranging between 500 s and 100 ks, for a total exposure time of almost 140 Ms. The catalog includes approximately 89 000 entries, of which almost 85 000 are not affected by pile-up and are not GRBs. Considering that many XRT fields were observed several times, we have a total of ~36 000 distinct celestial sources. We computed count rates in three energy bands: 0.3−10 keV (Full, or F), 0.3−3 keV (Soft, or S) and 2−10 keV (Hard, or H). Each entry has a detection in at least one of these bands. In particular, we detect ~80 000, ~70 000 and ~25 500 in the F, S and H band, respectively. Count rates were converted into fluxes in the 0.5−10, 0.5−2 and 2−10 keV bands. The flux interval sampled by the detected sources is 7.4 × 10-15 − 9.1 × 10-11, 3.1 × 10[Superscript: -15] − 1.1 × 10[Superscript: -11] and 1.3 × 10[Superscript: -14] − 9.1 × 10[Superscript: -11] erg cm[Superscript: -2 ]s[Superscript: -1] for the F, S and H band, respectively. Some possible scientific uses of the catalog are also highlighted