Coronal activity in F-, G-, and K-type stars. I. Relations between parameters characterizing stellar and activity.
Abstract
A sample of 66 stars, containing dwarfs and giants, is subjected to a multidimensional common-factor analysis. The parameters used are the soft X-ray flux density at the stellar surface Fx, the Ca II H + K line-core flux density FH+K, and parameters determining the stellar interior.
We find a high correlation between Fx and the Ca II H+K excess flux ΔFH+K, obtained by subtracting an observational lower limit from FM + K We argue, that the Ca ii lower-limit flux is uncorrelated with hot, X-ray emitting, magnetic structures. The common-factor analysis shows that, for the stars in the present sample, the relation between Fx and ΔFH+K does not depend on the stellar mass or radius. All stars included in the analysis - single dwarfs and giants, and components of short- period binaries - follow the relation over four decades in Fx: Fx(:)ΔF1.67H+K. The Sun follows this relation during its activity cycle, which suggests that structural changes occur on the Sun (as required by the nonlinearity of the above relation) similar to the structural differences between stars with different average levels of activity.- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- November 1983
- Bibcode:
- 1983A&A...127..289S
- Keywords:
-
- Dwarf Stars;
- F Stars;
- G Stars;
- Giant Stars;
- K Stars;
- Stellar Coronas;
- Stellar Magnetic Fields;
- Stellar Structure;
- Chromosphere;
- Factor Analysis;
- K Lines;
- Late Stars;
- Magnetoactivity;
- Stellar Spectra;
- Astrophysics