XMM-Newton observations of the M31 northern disk:: Properties of selected X-ray sources and unresolved emission

We present the results of an XMM-Newton survey of the northern part of M31 disk. The X-ray properties of the 37 brightest sources are studied in detail. Combining the results of X-ray analysis with available data at other wavelengths, we were able to identify 19 out of 37 sources. Two sources in our sample were previously unknown: the hard X-ray source XMMU J004415.8+413057 and a transient supersoft source XMMU J004414.1+412206. We report on the discovery of X-ray pulsations from the source XMMU J004415.8+413057 with a period of 197s. Three X-ray sources were identified with optical and radio SNR candidates. Five bright X-ray sources coincide with Galactic foreground stars. The properties of the remaining 18 bright X-ray sources detected in the survey are consistent with an AGN in the background of M31 and X-ray binaries belonging to M31. We report on the first unambiguous detection of the soft unresolved X-ray emission from the disk of M31. It follows the pattern of the spiral arms and can be traced up to the distance of similar to 10 kpc from the center of the galaxy. The spectrum of the unresolved emission shows dominant soft thermal component, which can be fit with a similar to 0.37 keV optically thin thermal plasma emission model or a combination of two thermal plasma models with temperatures of similar to 0.1 and similar to 0.7 keV. We suggest that significant part of the unresolved X-ray emission may represent hot diffuse gas and late-type stars in the disk of M31.