Nuclear burning in accreting neutron stars and X-ray bursts.
Abstract
The general properties of nuclear burning in accreting neutron stars are considered. The behavior expected in the pycnonuclear and thermonuclear regimes is discussed along with the conditions required for thermonuclear runaway, and the energy available from H, He, C, and O burning during an X-ray burst, assuming the burst arises from a thermonuclear flash. By using these results and making conservative assumptions, some constraints placed on such models of X-ray bursts by observation are derived. It is found that hydrogen burning appears to be ruled out as the source of the X-ray bursts. Indeed, no nuclear fuel is consistent with observed background luminosities if the fuel burned in a burst must be replenished by the time of the next burst. However, 'storage battery' models, in which the fuel is progressively used up, involving the burning of He, C, or O may be consistent with the observed properties of some burst sources, although not with those of the rapid burster MXB 1730-335. The eventual exhaustion of fuel in 'battery' models limits both the number of bursts that can occur in a single active state and the long-term ratio of burst-active to burst-inactive periods. Observational determinations of these quantities are important tests of nuclear-burning models.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- February 1978
- DOI:
- 10.1086/155905
- Bibcode:
- 1978ApJ...220..291L
- Keywords:
-
- Neutron Stars;
- Nuclear Fusion;
- Radio Bursts;
- Stellar Mass Accretion;
- X Ray Astronomy;
- Astronomical Models;
- Carbon;
- Helium;
- Hydrogen;
- Oxygen;
- Stellar Luminosity;
- Thermal Instability;
- Astrophysics;
- Accretion:Neutron Stars;
- Neutron Stars:Nuclear Burning;
- Neutron Stars:X-Ray Bursts