17.
On the rotation-activity correlation for active binary stars.
Gunn A.G., Mitrou C.K. & Doyle J.G.,
MNRAS, 1998, 296, 150.
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ABSTRACT. We present an investigation of rotation-activity
correlations using International Ultraviolet Explorer
(IUE) SWP measurements of the CIV emission line at 1550
Angstroms for 72 active binary systems. We use a standard stellar
evolution code to derive non-empirical Rossby numbers, Ro, for each
star in our sample and compare the resulting CIV rotation-activity
correlation to that found for empirically derived values of Rossby
number and that based on rotation alone. For dwarf stars our values
of Ro do not differ greatly from empirical ones and we find a
corresponding lack of improvement in correlation. Only a marginal
improvement 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
theoretical 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 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.
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