The X-ray emission of the sdO star BD+37 1977

While several hot subdwarf stars have been deeply investigated in the opticaland UV domain, up to very recent times only the sdO stars HD49798 and BD+37 442had been detected at Xrays. Both sources are characterized by comparablespectral and timing properties; in particular, the flux shows a fast periodicmodulation, likely due to wind accretion from the sdO star onto a WD or NScompanion. In the latest months the first systematic search for Xray emissionfrom a complete fluxlimited sample of sdO stars, performed by Chandra, hasprovided a detection also of the sdO star BD+37 1977. Now we propose to observethis star with XMM: our aim is to characterize in detail its spectral Xrayproperties and to investigate if it is intrinsic or due to an accreting compact companion. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]