Evidence for chromospheres and coronae in stars: recent observations, some unanswered theoretical questions, and a speculative scenario.
Abstract
The paper discusses recent UV and X-ray evidence for the existence of solar-type chromospheres, transition regions and coronae in stars other than the sun. The stellar spectral types associated with emission lines indicative of chromospheres and transition regions and X-ray fluxes indicative of coronae are examined, and the possibility of chromospheres and transition regions existing in stars hotter or cooler than the late-type stars is considered. The stellar parameters determining the properties of stellar chromospheres, transition regions and coronae are discussed, including varying magnetic fields, stellar rotation and convection zone parameters. A speculative scenario for the source of chromospheres, transition regions and coronae in O, B and A stars, late-type dwarfs, and G-M giants and supergiants is then presented which is based on the predominant role of magnetic fields in the nonradiative heating of outer atmospheres.
- Publication:
-
Solar Phenomena in Stars and Stellar Systems
- Pub Date:
- 1981
- Bibcode:
- 1981ASIC...68...99L
- Keywords:
-
- Chromosphere;
- Hertzsprung-Russell Diagram;
- Stellar Coronas;
- Stellar Spectra;
- Stellar Structure;
- Stellar Temperature;
- Emission Spectra;
- G Stars;
- Heao 2;
- Iue;
- Line Spectra;
- Stellar Rotation;
- Ultraviolet Spectra;
- X Ray Spectra;
- Astrophysics;
- Stellar Chromospheres;
- Stellar Coronae