The minimum orbital period for ultra-compact binaries with the helium burning secondaries.
Abstract
Based on the model of the binary 1E 2259 + 586, evolutionary calculations of an ultra-compact binary system undergoing mass transfer, with a helium-burning 0.6 M secondary and a 1.3 M neutron star primary in a tight orbit of 37 minutes, are presented. It is assumed that the total system mass is constant, and that the total orbital angular momentum is conserved apart from gravitational radiation losses. Heavy mass transfer peaks at a value of 10 to the -7th M/yr when a minimum orbital period of about 11 minutes is approached, at which time the helium is extinguished and the star reaches a state of severe thermal imbalance. The secondary then has a mass of 0.2 M and remains semi-degenerate for much of the further evolution of the binary system during which the binary separation increases again. Tidal stability requires that a substantial part of the mass transferred at a super-Eddington rate is captured and accreted by the heavier neutron star.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- January 1986
- Bibcode:
- 1986A&A...155...51S
- Keywords:
-
- Pulsars;
- Stellar Evolution;
- Stellar Mass Accretion;
- Stellar Orbits;
- Stellar Temperature;
- X Ray Binaries;
- Angular Momentum;
- Companion Stars;
- Gravitational Waves;
- Stellar Mass;
- Stellar Models;
- Astrophysics