Minimum-flux coronal models for hydrogen and helium white dwarf atmospheres.
Abstract
Families of zero-mass-loss coronal models based on the minimum-flux prescription of Hearn (1975), in which bound-bound, bound-free, and free-free radiative processes with their differing emissivity vs. temperature laws are included, have been computed. These models are applied to the case of white-dwarf envelopes of pure hydrogen or helium, and the results are expressed as relationships between the required total energy flux, the coronal base pressure, and its temperature. The soft X-ray detection of Sirius by the ANS group is discussed. If all the X-ray flux is ascribed to a minimum-flux hydrogen corona surrounding the white dwarf Sirius B, it must have a temperature of 1.6 + or -0.3 million K and a base pressure of 110,000 + or - 40,000 dyne/sq cm. The surface energy flux needed to heat such a corona is (9 + or - 5) x 10 to the 10th erg/sq cm per sec.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- September 1979
- Bibcode:
- 1979A&A....78..104L
- Keywords:
-
- Helium;
- Hydrogen;
- Stellar Atmospheres;
- Stellar Coronas;
- Stellar Models;
- White Dwarf Stars;
- Emission Spectra;
- Energy Dissipation;
- Line Spectra;
- Optical Thickness;
- Stellar Radiation;
- Stellar Spectra;
- Stellar Structure;
- Stellar Temperature;
- X Ray Spectra;
- Astrophysics;
- Atmospheres:White Dwarfs;
- Helium:Stellar Coronae;
- Hydrogen:Stellar Coronae;
- Stellar Coronae:Models