The discovery of 13 s X-ray pulsations from the hydrogen depleted subdwarf O6 star binary HD49798

We discovered strong 13 s pulsations in the X-ray flux of HD49798 (Israel et al. 1995), a 1.55 d single-component spectroscopic binary containing a hydrogen depleted subdwarf O6 star. The source X-ray spectrum is extremely soft, corresponding to an unabsorbed 0.1–2 keV luminosity of a few × 10 32 er...

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Bibliographic Details
Published in:Advances in space research 1998-01, Vol.22 (7), p.1035-1038
Main Authors: Israel, G.L., Stella, L., Angelini, L., White, N.E., Kallman, T.R., Giommi, P., Treves, A.
Format: Article
Language:English
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Summary:We discovered strong 13 s pulsations in the X-ray flux of HD49798 (Israel et al. 1995), a 1.55 d single-component spectroscopic binary containing a hydrogen depleted subdwarf O6 star. The source X-ray spectrum is extremely soft, corresponding to an unabsorbed 0.1–2 keV luminosity of a few × 10 32 erg s −1 (distance of 650 pc). A higher luminosity might be hidden in the EUV. Our results imply that the unseen companion is an accreting degenerate star, either a white dwarf or a neutron star. In either case HD49798 corresponds to a previously unobserved evolutionary stage of a massive binary system, after common envelope and spiral-in.
ISSN:0273-1177
1879-1948
DOI:10.1016/S0273-1177(98)00139-2