Stellar activity in synchronized binaries. I. Dependence on rotation.

Abstract

The authors have examined a large sample of late-type binaries with orbital periods from 1 to 100 days for relationships between stellar activity and rotation period, which is assumed to be synchronized with the stellar orbital period. Most of the systems are in the RS Canum Venaticorum class of close binaries. The activity diagnostics were observed with the IUE and the Einstein Observatory and range from the mid-chromosphere to the corona. There is a dependence of activity on rotation in the synchronized binaries; surface flux is the preferable measure of activity. This dependence is approximately linear in the corona and rather weak in the chromosphere (intermediate for the transition region). These results for binaries are compared with those for single stars.