On the X-ray source luminosity distributions in the bulge and disk of   M31: First results from XMM-Newton survey
  We present luminosity distributions for the X-ray sources detected with XMM-Newton in the bulge and disk of the Andromeda Galaxy (M31). The disk is clearly lacking the brighter sources which dominate X-ray emission from the bulge. This is the first convincing evidence for a difference between bulge and disk X-ray populations in M31. Our results are in good qualitative agreement with the luminosity distributions for low- and high-mass X-ray binaries recently obtained by Grimm et al.(2001) for our Galaxy. This confirms that X-ray population of the disk of M31 is dominated by fainter HMXB sources, while the bulge is populated with brighter LMXBs. 
Sergey Trudolyubov (1,2), Konstantin Borozdin (1,2), William   Priedhorsky (1), Keith Mason (3), France Cordova (4) ((1) LAN...