Chandra X-ray sources in M101

A deep (98.2 ks) Chandra Cycle 1 observation has revealed a wealth of discr ete X-ray sources as well as diffuse emission in the nearby face-on spiral galaxy M101. From this rich data set we have created a catalog of the 110 s ources from the S3 chip detected with a significance of greater than 3 sigm a. This detection threshold corresponds to a flux of similar to 10(-16) erg s cm(-2) s(-1) and a luminosity of similar to 10(36) ergs s(-1) for a dista nce to M101 of 7.2 Mpc. The sources display a distinct correlation with the spiral arms of M101 and include a variety of X-ray binaries, supersoft sou rces, supernova remnants, and other objects of which only similar to 27 are likely to be background sources. There are only a few sources in the inter arm regions, and most of these have X-ray colors consistent with that of ba ckground active galactic nuclei. The derived log N-log S relation for the s ources in M101 (background subtracted) has a slope of -0.80 +/- 0.05 over t he range of 10(36)-10(38) ergs s(-1). The nucleus is resolved into two near ly identical X-ray sources, each with a 0.5-2.0 keV flux of 4 x 10(37) ergs s(-1). One of these sources coincides with the optical nucleus, and the ot her coincides with a cluster of stars 110 pc to the south. The field includ es 54 optically identified supernova remnants (SNRs), of which 12 are detec ted by Chandra. Two of the SNR sources are variable and hence must be compa ct objects. In total, eight of the X-ray sources show evidence for short-te rm temporal variation during this observation. Two of these variable source s are now brighter than the ROSAT detection threshold, but they were not de tected in the previous ROSAT observations taken in 1992 and 1996. There are also two variable sources previously seen with ROSAT that apparently have faded below the Chandra detection threshold. The brightest source in the fi eld shows extreme long-term and short-term temporal variability. At its pea k brightness it has a super-Eddington luminosity greater than 10(39) ergs s (-1). There are 10 supersoft sources (SSSs) in the field, which can be divi ded into two distinct subclasses : the brighter class (three objects) has a luminosity of similar to 10(38) ergs s(-1) and a blackbody temperature of similar to 70 eV, whereas the other class (seven objects) is an order of ma gnitude fainter and has a blackbody temperature of only similar to 50 eV.