Chromospheric MG II emission in A5 to K4 main sequence stars from high resolution IUE spectra.
Abstract
Observations of the emission cores of the Mg II resonance doublet for 11 main sequence stars in the spectral type range A5-K5 obtained with the IUE satellite at 0.2 A resolution are discussed. Calibrated observed fluxes are used to evaluate the Mg II chromospheric losses as they correlate with effective temperature convection and rotation and other chromospheric indicators. Mg II emission and therefore chromosphere are found on main sequence stars as early as A7, B-V equals 0.22 m. The chromospheric radiative losses from the h and k line are discussed in terms of the effective temperature and the rotation period. The k line flux normalized to the bolometric flux appears to be independent of the effective temperature. There is evidence of an exponential decrease of the Mg II flux as the rotation period increases, not dependent on the spectral type. The Mg II/Ca II flux ratio decreases in stars of higher losses as it does in solar plages of higher brightness.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- November 1982
- Bibcode:
- 1982A&A...115..280B
- Keywords:
-
- Chromosphere;
- Iue;
- Magnesium;
- Main Sequence Stars;
- Stellar Spectra;
- Ultraviolet Spectra;
- Data Reduction;
- Emission Spectra;
- Fine Structure;
- High Resolution;
- K Lines;
- Stellar Atmospheres;
- Stellar Rotation;
- Astrophysics