  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.
