The stellar wind of hot subdwarf stars

All we know about hot subdwarf (sd) stars is based on studies in the optical andUV domain, while none of them has been detected at Xrays. The only exception isthe sdO binary HD49798, in which the WD companion shows a significant Xrayemission, due to the matter accreted from the sd primary. A recent XMMobservation of this source has revealed a significant Xray emission also duringthe eclipse phase, when the WD is obscured by the primary subdwarf, thussuggesting that the observed Xray flux is due to the subdwarf itself. In orderto investigate if also other sdO stars are characterized by an intrinsic Xrayemission, we propose to observe BD+37 442: it is a nearby and bright sdO starwith a strong stellar wind, therefore it is the best candidate to perform this type of search. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]