Low-Mass Normal-Matter Atmospheres of Strange Stars and Their Radiation
Abstract
The quark surface of a strange star has a very low emissivity for X-ray photons. I find that a small amount of normal matter at the quark surface with temperature in the range 107 K <~ TS << mc2/k ~= 6 × 109 K is enough to produce X-rays with high luminosity LX ~= (1032-1034)[ΔM/(10-22 Msolar)]2 ergs s-1. For a total atmospheric mass ΔM ~ 10-20 to 10-19 Msolar, this luminosity may be as high as the Eddington limit. The mean energy of X-ray photons that are radiated from such a low-mass atmosphere of a strange star is ~102[TS/(108 K)]0.45, ~=30-300 times greater than the mean energy of X-ray photons that are radiated from the surface of both a neutron star and a strange star with a massive normal-matter envelope, ΔM ~ 10-5 Msolar, for a fixed temperature at the stellar core. This raises the possibility that some black hole candidates with hard X-ray spectra are, in fact, such strange stars with a low-mass atmosphere. The X-ray emission from single strange stars is estimated.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 1997
- DOI:
- 10.1086/310657
- arXiv:
- arXiv:astro-ph/9703037
- Bibcode:
- 1997ApJ...481L.107U
- Keywords:
-
- STARS: ATMOSPHERES;
- X-RAYS: STARS;
- RADIATION MECHANISMS: THERMAL;
- Radiation Mechanisms: Thermal;
- Stars: Atmospheres;
- X-Rays: Stars;
- Astrophysics
- E-Print:
- Accepted for publication in The Astrophysical Journal Letters, AAS LATEX macroc v4.0, 9 pages