The X-ray emission of the sdO stars Feige 34 and BD+28 4211

The XMM observation of HD49798, BD+37 442, and BD+37 1977 allowed us tocharacterize their spectral and timing properties, and to attribute the observedflux to wind accretion from the sdO star onto a WD or NS companion and/or toturbulence and shocks in the stellar wind of the sdO star itself. A Chandrasurvey of a complete fluxlimited sample of sdO stars provided a clear detectionalso of the sdO stars BD+28 4211 and Feige 34. While the former subdwarfs areluminous and Herich sdO stars, the latter ones are compact Hepoor stars. Theyare the first stars of this type detected at Xrays; therefore, now we proposeto observe with XMM also BD+28 4211 and Feige 34. This proposal was alreadyaccepted in priority C for the AO14 and AO15 observing periods, but no observation has been made to date. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]