The Discovery of 13 second X-Ray Pulsations from the Hydrogen-depleted Subdwarf O6 Star Binary HD 49798
Open Access
- 1 January 1997
- journal article
- research article
- Published by American Astronomical Society in The Astrophysical Journal
- Vol. 474 (1) , L53-L56
- https://doi.org/10.1086/310418
Abstract
We have discovered strong ~13 s X-ray pulsations in the ROSAT Position Sensitive Proportional Counter light curve of HD 49798, a 1.55 day single-component spectroscopic binary containing a hydrogen-depleted subdwarf O6 star. We find no evidence for period changes during the ~4 hr ROSAT pointing. The source X-ray spectrum is extremely soft, with an unabsorbed 0.1-2 keV luminosity of a few times 1032 ergs 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, a white dwarf, or, more likely, a neutron star. In any case, HD 49798 corresponds to a previously unobserved evolutionary stage of a massive binary system after the common-envelope phase and spiraling in.Keywords
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This publication has 12 references indexed in Scilit:
- Princeton-Arecibo Declination-Strip Survey for Millisecond Pulsars. I.The Astrophysical Journal, 1996
- A New Technique for the Detection of Periodic Signals in ``Colored'' Power SpectraThe Astrophysical Journal, 1996
- Quasi-Coherent Oscillations in the Extreme Ultraviolet Flux of the Dwarf Nova SS CygniThe Astrophysical Journal, 1996
- ROSAT observations of a soft X-ray emission component in the intermediate polar RE 0751+14Monthly Notices of the Royal Astronomical Society, 1994
- The discovery of a brake on the white dwarf in AE AquariiMonthly Notices of the Royal Astronomical Society, 1994
- Discovery of three binary millisecond pulsarsThe Astrophysical Journal, 1994
- The EXOSAT observations of SS CygniMonthly Notices of the Royal Astronomical Society, 1992
- X-ray spectra of cataclysmic variables from the Einstein ObservatoryThe Astrophysical Journal, 1991
- The ultraviolet calibration of the Hubble Space Telescope. IV - Absolute IUE fluxes of Hubble Space Telescope standard starsThe Astrophysical Journal Supplement Series, 1990
- Soft X-ray pulsations from SS CygniThe Astrophysical Journal, 1980