The cool Half of the H-R diagram in soft X-rays.
Abstract
The results of an Einstein Observatory program to map the occurrence of hot coronae (T greater than 1 million K) in the cool half of the Hertzsprung-Russell diagram are reported. F-M dwarfs, and late F through early K star giants characterized by 10,000 K chromospheric and 20,000-200,000 K FUV emission lines were studied in one region, while a second region study included red giants later than K2 III and supergiants later than G5 Ib with weaker chromospheric emission and no high temperature species. Program goals comprised determination of the C IV division as seen in soft X-rays, and identification of stellar parameters which distinguish strong from weak coronal X-ray sources. A summary of target stars, X-ray fluxes, and UV emission profiles is provided, and coronal emissions, comparisons of C IV and wind boundaries, hybrid-spectrum supergiants, the energy balance of stellar outer atmospheres, stellar rotation and coronae, and evolutionary considerations are discussed, along with lines of future research.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 1981
- DOI:
- 10.1086/159374
- Bibcode:
- 1981ApJ...250..293A
- Keywords:
-
- Hertzsprung-Russell Diagram;
- Late Stars;
- Stellar Coronas;
- Stellar Temperature;
- X Ray Sources;
- Dwarf Stars;
- F Stars;
- Giant Stars;
- K Stars;
- Stellar Magnetic Fields;
- Stellar Rotation;
- Stellar Winds;
- Astrophysics