Discovery of a compact companion to the hot subdwarf star BD+37 442
  We report the results of the first X-ray observation of the luminous and helium-rich O-type subdwarf BD+37 442, carried out with the XMM-Newton satellite in August 2011. X-ray emission is detected with a flux of about 3x10^(-14) erg/cm2/s (0.2-1 keV) and a very soft spectrum, well fit by the sum of a blackbody with temperature kT_BB = 45^(+11)_(-9) eV and a power law with a poorly constrained photon index. Significant pulsations with a period of 19.2 s are detected, indicating that the X-ray emission originates in a white dwarf or neutron star companion, most likely powered by accretion from the wind of BD+37 442. 
N. La Palombara (1), S. Mereghetti (1), A. Tiengo (1,2), P. Esposito   (3) ((1) INAF/IASF Milano, (2) IUSS Pavia, (3) INAF/O...
astro-ph.HE astro-ph.SR