Ellipsoidal light variations and masses of X-ray binaries.
Abstract
The ellipsoidal light curves of four binary X-ray systems (HDE 226868/Cyg X-1, Sk 160/ SMC X-1, Krzeminski's star/Cen X-3, and HZ Her/Her X-1) are analyzed assuming that the light variations are caused by gravitational and limb-darkening effects on a tidally distorted star. Some uncertainties regarding the validity of this interpretation are discussed, including departures from repeatability in the light curve and from corotation, the effects of heating and reflection, and the possibility that the primary is inside the Roche lobe. Numerical calculations of light curves show that Cyg X-1 can be either a black hole or a normal early-type star with a mass not less than 9 solar masses; the mass of SMC X-1 is about 2.3 solar masses, close to the upper limit for a nonrotating neutron star; and the mass of Cen X-3 is between 0.6 and 1.1 solar masses. No significant constraints could be derived from the available data for Her X-1.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 1975
- DOI:
- 10.1086/153558
- Bibcode:
- 1975ApJ...197..675A
- Keywords:
-
- Binary Stars;
- Light Curve;
- Optical Properties;
- Stellar Mass;
- X Ray Binaries;
- X Ray Sources;
- Black Holes (Astronomy);
- Early Stars;
- Gravitational Effects;
- Neutron Stars;
- Roche Limit;
- Stellar Luminosity;
- X Ray Stars;
- Astrophysics