On the mass determination of Hercules X-1.
Abstract
Middleditch and Nelson (1976) obtained a value of 1.30 + or - 0.14 solar masses for the mass of Her X-1 on the basis of the observed frequencies of the optical pulsations due to absorption, reprocessing, and reemission of pulsed X-ray energy from the surface of HZ Her. A more conventional estimate of the uncertainty in the mass inferred for Her X-1 from the cited optical-pulsation data is computed using those data in combination with a simple geometrical model for the optical pulsations and Uhuru X-ray observations of the mass function and the half-angle of the eclipse duration of the HZ Her/Her X-1 system. It is assumed that the surface of HZ Her is an equipotential surface of the restricted three-body potential and that HZ Her just fills its critical equipotential. The allowed ranges of masses obtained are 0.6 to 2.0 solar masses for Her X-1 and 1.6 to 2.7 solar masses for HZ Her. It is found that the calculated mass of Her X-1 is especially sensitive to the unknown rotational velocity of HZ Her.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 1977
- DOI:
- 10.1086/182468
- Bibcode:
- 1977ApJ...215L..21B
- Keywords:
-
- Eclipsing Binary Stars;
- Stellar Mass;
- X Ray Stars;
- Angular Velocity;
- Light Curve;
- Stellar Models;
- Stellar Rotation;
- Astrophysics