EUV line emission as a diagnostic of atmospheres of cool giant stars
Abstract
A number of cool giant and supergiant stars have been observed with the IUE satellite. Wavelengths, line widths and fluxes of emission lines in these spectra are measured, using a least squares Gaussian fitting technique. Hot transition region lines are redshifted by 10 - 20 km/s relative to cold chromospheric lines. This effect increases with stellar activity. The gas densities in these stellar atmospheres are so low that radiative processes, and in particular resonance fluorescence, are the dominant excitation mechanisms. One important example is the pumping of S I by O I. The effectiveness of this process increases with decreasing gas density.
- Publication:
-
New Insights in Astrophysics. Eight Years of UV Astronomy with IUE
- Pub Date:
- September 1986
- Bibcode:
- 1986ESASP.263..129J
- Keywords:
-
- Cool Stars;
- Extreme Ultraviolet Radiation;
- Giant Stars;
- Line Spectra;
- Stellar Atmospheres;
- Stellar Spectra;
- Iue;
- Red Shift;
- Spectral Energy Distribution;
- Spectral Line Width;
- Stellar Activity;
- Astronomy