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

Context. The Swift satellite is a multi-wavelength observatory specifically d esigned for gamma-ray burst (GRB) astronomy that is operational since 2004. Swift is also a very flexible multi-p urpose facility that supports a wide range of scientific field s such as active galactic nuclei, supernovae, cataclysmic variables, Gala ctic transients, active stars and comets. The Swift X-ray Telescope (XRT) has collected more than 150 Ms of observations in its first seven y ears of operations. Aims. The purpose of this work is to present to the scientific commun ity the list of all the X-ray point sources detected in XRT imaging data taken in photon counting mode during the first se ven years of Swift operations. All these point-like sources , excluding the Gamma-Ray Bursts (GRB), will be stored in a catalog publicly available (1SWXRT). Methods. We consider 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 an d the corresponding uncertainties were computed. Results. We have analyzed more than 35,000 XRT fields, with exposures r anging 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 seve ral 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 partic ular, 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 −15 − 1.1× 10 −11 and 1.3× 10 −14 − 9.1× 10 −11 erg cm −2 s −1 for the F, S and H band, respectively. Some possible scientific uses of the cat alog are also highlighted.