The Discovery of 13 second X-Ray Pulsations from the Hydrogen-depleted Subdwarf O6 Star Binary HD 49798 | Zendy

G. L. Israel | Zendy; L. Stella | Zendy; L. Angelini | Zendy; N. E. White | Zendy; T. R. Kallman | Zendy; P. Giommi | Zendy; A. Treves | Zendy

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The Discovery of 13 second X-Ray Pulsations from the Hydrogen-depleted Subdwarf O6 Star Binary HD 49798

Author(s) -

G. L. Israel,

L. Stella,

L. Angelini,

N. E. White,

T. R. Kallman,

P. Giommi,

A. Treves

Publication year - 1997

Publication title -

the astrophysical journal

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 2.376

H-Index - 489

eISSN - 1538-4357

pISSN - 0004-637X

DOI - 10.1086/310418

Subject(s) - subdwarf , astrophysics , rosat , physics , white dwarf , neutron star , luminosity , astronomy , light curve , x ray binary , binary number , star (game theory) , binary star , common envelope , stars , galaxy , arithmetic , mathematics

We discovered strong 13s X-ray pulsations in the public Rosat PSPC lightcurve of HD49798, a 1.55d single-component spectroscopic binary containing ahydrogen depleted subdwarf O6 star. We find no evidence for period changesduring the about 4hr Rosat pointing. The source X-ray spectrum is extremelysoft, 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. Ourresults imply that the unseen companion is an accreting degenerate star, awhite dwarf or, more likely, a neutron star. In either case HD49798 correspondsto a previously unobserved evolutionary stage of a massive binary system, aftercommon envelope and spiral-in.Comment: 10 pages plus 2 postscript figures. AASTeX. Accepted for publication in the Astrophysical Journal Letter

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