XMM northern disc of M31 sources

We also checked for variability. In order to classify the sources detected in the new deep XMM-Newton observations, we cross-correlated the source list with the source catalogue of a new survey of the northern disc of M31 carried out with the Chandra X-ray Observatory and the Hubble Space Telescope (Panchromatic Hubble Andromeda Treasury, PHAT) as well as with other existing catalogues We detected a total of 389 sources in the two fields of the northern disc ofM31 observed with XMM-Newton.We identified 43 foreground stars and candidates and 50 background sources.

Based on the comparison to the results of the Chandra/PHAT survey, we classify 24 hard X-ray sources as new candidates for X-ray binaries (XRBs). In total, we identified 34 X-ray binaries and candidates and 18 supernova remnants (SNRs) and candidates. We studied the spectral properties of the four brightest SNRs and confirmed five new X-ray SNRs.

Three of the four SNRs, for which a spectral analysis was performed, show emission mainly below 2 keV, which is consistent with shocked ISM. The spectra of two of them also require an additional component with a higher temperature. The SNR [SPH11] 1535 has a harder spectrum and might suggest that there is a pulsar-wind nebula inside the SNR.

For all SNRs in the observed fields, we measured the X-ray flux or calculated upper limits. We also carried out short-term and long-term variability studies of the X-ray sources and found five new sources showing clear variability. In addition, we studied the spectral properties of the transient source SWIFT J004420.1+413702, which shows significant variation in flux over a period of seven months (June 2015 to January 2016) and associated change in absorption.

Based on the likely optical counterpart detected in the Chandra/PHAT survey, the source is classified as a low-mass X-ray binary.