Hα Photometry of Dwarf K and M Stars: Chromospheric Activity
Abstract
H-alpha photometry of 118 K and M dwarfs are presented, with H-alpha equivalent width measures accurate to about 0.05 A. The data are combined with the spectroscopic surveys of Stauffer and Hartmann (1986) and Fleming et al. (1988) to study the main features of the chromospheric activity versus mass relation for low-mass stars. An upper bound to the H-alpha equivalent width is found to be a function of the mass relation (R-I). H-alpha luminosities and surface fluxes are calculated for active stars, showing that both quantities generally decline with R-I. The upper bound to the fraction of a star's bolometric luminosity, however, is independent of R-I. The results suggest that the chromospheres of most dMe stars with R-I less than 1.1 are in an activity-saturated state. Also, H-alpha variability, probably due to flares, is detected in several stars.
- Publication:
-
The Astronomical Journal
- Pub Date:
- March 1989
- DOI:
- 10.1086/115035
- Bibcode:
- 1989AJ.....97..891H
- Keywords:
-
- Chromosphere;
- Dwarf Stars;
- H Alpha Line;
- K Stars;
- M Stars;
- Stellar Activity;
- Absorption Spectra;
- Bolometers;
- Spectral Line Width;
- Stellar Luminosity;
- Stellar Spectrophotometry;
- Astrophysics;
- STARS: LATE-TYPE;
- STARS: CHROMOSPHERES