Chromospheric activity, kinematics, and metallicities of nearby M dwarfs

Abstract

Attention is given to the results of more than 1000 observations of about 200 Gliese (1969) catalog M dwarfs, whose BVRIJHK photometry is believed to be accurate to 0.015 mag in each bandpass. An analysis of these data indicates that the H-alpha equivalent widths are a useful chromospheric indicator for M dwarfs; as the chromosphere increases in strength, the H-alpha absorption equivalent width first increases, then decreases, and H-alpha finally goes into emission, as predicted by Gram and Mullan (1979) for M dwarf chromospheres. The present JHK photometry is used to identify stars with metallicities that are significantly different from that of the sun. It is noted that dMe stars in this sample generally have young disk motions, are more luminous than dM stars of the same color, and have B-V colors that are too blue for their V-I color.