The 10830 Angstrom Chromospheric Line of Helium in Bright Stars
Abstract
Results of a survey of the chromospheric line He I 10830 A in sixty F, G, and K giants are presented. A weak He line appears in middle and late F supergiants, increases greatly in strength by spectral type G0, appears in all observed K stars, and disappears around type M1. Many of the less luminous K stars show a constant 10830 A line which appears similar in shape to that seen in the sun. Stars showing this profile lie to the left of a well-defined boundary in the H-R diagram. Most of the luminous and cooler K stars to the right of this boundary line show highly variable He I profiles; variations on a time scale of a month are common. Observations suggest episodic ejection of matter and a subsequent return of some fraction of this matter to the photosphere in these stars. The non-LTE radiative transfer problem for helium in a stellar chromosphere is modelled.
- Publication:
-
The Astrophysical Journal Supplement Series
- Pub Date:
- December 1986
- DOI:
- 10.1086/191160
- Bibcode:
- 1986ApJS...62..899O
- Keywords:
-
- Chromosphere;
- Giant Stars;
- Helium;
- Infrared Astronomy;
- Stellar Spectra;
- F Stars;
- G Stars;
- Hertzsprung-Russell Diagram;
- K Stars;
- M Stars;
- Photoionization;
- Spectral Line Width;
- Stellar Activity;
- Stellar Coronas;
- Stellar Envelopes;
- Supergiant Stars;
- Telluric Lines;
- Thermodynamic Equilibrium;
- Variable Stars;
- Astrophysics;
- INFRARED: SPECTRA;
- STARS: ATMOSPHERES;
- STARS: CHROMOSPHERES;
- STARS: MASS LOSS