A Large Spectral Class Dependence of the Wilson-Bappu Effect among Luminous Stars (original) (raw)
ADS
Abstract
The striking correlation between Ca II K-line emission width and absolute visual magnitude has not previously been well calibrated for stars more luminous than giants. From a sample of binary systems fit to isochrones, we find deviations of more than 2 mag, correlated with spectral class, between these binarity Mv values and the Wilson-Bappu relation. Additional Mv values derived from Hipparcos parallaxes are used to explore the systematics. The spectral class dependence vanishes for K-line parameter logW0<=1.80. Linear spectral class corrections are derived for the more luminous stars, with logW0>=2.00, while a table is provided for the transition region. The dispersion from these relations is about +/-0.6 mag. This recalibration extends the demonstrated applicability of the Wilson-Bappu technique to Mv~=-5 or distance ~20 kpc.
Publication:
Publications of the Astronomical Society of the Pacific
Pub Date:
February 2001
DOI:
Bibcode:
Keywords:
- Stars: Binaries: Spectroscopic;
- Stars: Chromospheres;
- Stars: Distances;
- Stars: Fundamental Parameters;
- Stars: Late-Type;
- Stars: Supergiants