Summary: Mon. Not. R. Astron. Soc. 000, 000--000 (0000) Printed 11 November 1997 (MN L a T E X style file v1.4)
On the rotation­activity correlation for active binary stars
A. G. Gunn 1;2? , C. K. Mitrou 2;3 and J. G. Doyle 2
1 University of Manchester, Nuffield Radio Astronomy Laboratories, Jodrell Bank, Macclesfield, Cheshire, SK11 9DG, UK
2 Armagh Observatory, College Hill, Armagh, BT61 9DG, N. Ireland
3 Section of Astrophysics, Astronomy and Mechanics, Dept. of Physics, University of Athens, Athens 15783, Greece
Accepted 1997 Received 1997 in original form June 1997
ABSTRACT
We present an investigation of rotation­activity correlations using IUE SWP mea­
surements of the Civ emission line at 1550 š Afor 72 active binary systems. We use a
standard stellar evolution code to derive non­empirical Rossby numbers, R o , for each
star in our sample and compare the resulting Civ rotation­activity correlation to that
found for empirically derived values of Rossby number and that based on rotation
alone. For dwarf stars our values of R o do not differ greatly from empirical ones and
we find a corresponding lack of improvement in correlation. Only a marginal improve­
ment in correlation is found for evolved components in our sample. We discuss possible
additional factors, other than rotation or convection, that may influence the activity
levels in active binaries. Our observational data implies, in contrast to the theoreti­
cal predictions of convective motions, that activity is only weakly related to mass in
evolved stars. We conclude that current dynamo theory is limited in its application

Source: Armagh Observatory

Collections: Physics