SIMBAD references

2017MNRAS.466.2918M - Mon. Not. R. Astron. Soc., 466, 2918-2921 (2017/April-2)

The lack of X-ray pulsations in the extreme helium star BD+37°442 and its possible stellar wind X-ray emission.


Abstract (from CDS):

We report the results of a new XMM-Newton observation of the helium-rich hot subdwarf BD+37°442 carried out in 2016 February. The possible periodicity at 19 s seen in a 2011 shorter observation is not confirmed, thus dismissing the evidence for a binary nature. This implies that the observed soft X-ray emission, with a luminosity of a few 1031 erg s–1, originates in BD+37°442 itself, rather than in an accreting neutron star companion. The X-ray spectrum is well fit by thermal plasma emission with a temperature of 0.22 keV and non-solar element abundances. Besides the overabundance of He, C and N already known from optical/UV studies, the X-ray spectra indicate also a significant excess of Ne. The soft X-ray spectrum and the ratio of X-ray to bolometric luminosity, LX/LBOL ∼ 2 x 10–7, are similar to those observed in massive early-type stars. This indicates that the mechanisms responsible for plasma shock-heating can work also in the weak stellar winds (mass-loss rates {dot}M_ W_≤10–8 M yr–1) of low-mass hot stars.

Abstract Copyright: © 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society

Journal keyword(s): stars: individual: BD+37 442 - subdwarfs - subdwarfs

Simbad objects: 6

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