A non-empirical rotation--activity correlation for active binaries
Abstract
We present an investigation of rotation-activity correlations using IUE SWP measurements of the CIV emission line at 1550AA for 72 active binary systems. We use a standard stellar evolution code to derive non-empirical Rossby numbers for each system. We compare the resulting rotation--CIV activity correlation to that found for empirically derived Rossby numbers and to the one based on period only. The marginal only improvement in the correlation that we find, is surprising considering that the empirically derived Rossby numbers were for main-sequence stars and should not be appropriate for evolved stars. This suggests an additional factor (other than rotation and convective motion) influencing the activity levels. Our observational data imply that activity is only weakly related to mass in evolved stars, in contrast to the theoretical predictions of convection zone motions. We conclude that current dynamo theory is limited in its application to the study of active stars, because of the uncertainty in the angular velocity--depth profile in stellar interiors and the unknown effects of binarity and surface gravity.
- Publication:
-
Joint European and National Astronomical Meeting
- Pub Date:
- 1997
- Bibcode:
- 1997jena.confE.145G