X-Ray Spectra from Neutron Stars Accreting at Low Rates
Abstract
The spectral properties of X--ray radiation produced in a static atmosphere around a neutron star accreting at very low rates are investigated. Previous results by Alme \& Wilson (1973) are extended to the range $10^{-7}\leq L/L_{Edd}\leq 10^{-3}$ to include the typical luminosities, $L\sim 10^{31}-10^{32} \ {\rm ergs\, s^{-1}}$, expected from isolated neutron stars accreting the interstellar medium. The emergent spectra show an overall hardening with respect to the blackbody at the neutron star effective temperature in addition to a significant excess over the Wien tail. The relevance of present results in connection with the observability of low--luminosity X--ray sources is briefly discussed.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- February 1995
- DOI:
- 10.1086/175223
- arXiv:
- arXiv:astro-ph/9407067
- Bibcode:
- 1995ApJ...439..849Z
- Keywords:
-
- Accretion Disks;
- Interstellar Matter;
- Mathematical Models;
- Neutron Stars;
- Stellar Luminosity;
- X Ray Spectra;
- X Ray Stars;
- Bremsstrahlung;
- Coulomb Collisions;
- Eddington Approximation;
- Photons;
- Stellar Atmospheres;
- Astrophysics;
- ACCRETION;
- ACCRETION DISKS;
- RADIATION MECHANISMS: NONTHERMAL;
- STARS: NEUTRON;
- X-RAYS: STARS;
- Astrophysics
- E-Print:
- 14 pages (3 postscript figures available on request), PlainTex, submitted to ApJ