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

Preprint

17 October 1996

preprint
Published by arXiv in arXiv

https://doi.org/10.48550/arXiv.astro-ph/9610139

Abstract

We discovered strong 13s X-ray pulsations in the public Rosat PSPC light curve of HD49798, a 1.55d single-component spectroscopic binary containing a hydrogen depleted subdwarf O6 star. We find no evidence for period changes during the about 4hr Rosat pointing. The source X-ray spectrum is extremely soft, with an unabsorbed 0.1-2keV luminosity of a few times 10^32 erg s^-1 (distance of 650pc). A higher luminosity might be hidden in the EUV. Our results imply that the unseen companion is an accreting degenerate star, a white dwarf or, more likely, 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.

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Version 1, 1996-10-17, ArXiv
Published version: The Astrophysical Journal, 474 (1), L53.

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