A survey of chromospheric emission and rotation among solar-type stars in the solar neighborhood

Abstract

A spectroscopic survey of Ca II and H and K emission among late-type dwarfs is analyzed in order to identify solar neighborhood stars with (B-V) greater than 0.50 and less than 1.00. The observations were used to calculate RHK, the fraction of the bolometric luminosity of a star which appears as HK emission. The angular velocities of the stars relative to the sun (Omega/Omega solar radius) were calculated based on a calibration of RHK with the Rossby number. The relationship between age and the rotational properties of the stars was also analyzed in detail. It is shown that for stars of a given RHK, age RHK increases slightly with increasing (B-V). The activity-age relation (RHK varies as exp -1/2) was found to be independent of mass for the late-type dwarfs. The rotation-age relation was also independent of mass, and the rotation rate of the sun was found to be normal for a star of its mass and age. It is suggested that the age dependencies of chromospheric activity are also unrelated to mass and angular momentum loss may be considered a self-regulating mechanism which is not related to the details of stellar structure such as the convective zone depth.