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Learning about Stellar Dynamos from Long–term Photometry of Starspots

Published online by Cambridge University Press:  12 April 2016

Douglas S. Hall
Douglas S. Hall*
Affiliation:
Center of Excellence, Tenessee State University, Nashville, Tennessee 37203

Abstract

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Spottedness, as evidenced by photometric variability in 277 late-type binary and single stars, is found to occur when the Rossby number is less than about 2/3. This holds true when the convective turnover time versus B–V relation of Gilliland is used for dwarfs and also for subgiants and giants if their turnover times are twice and four times longer, respectively, than for dwarfs. Differential rotation is found correlated with rotation period (rapidly rotating stars approaching solid-body rotation) and also with lobe-filling factor (the differential rotation coefficient k is 2.5 times larger for F = 0 than F = 1). Also reviewed are latitude extent of spottedness, latitude drift during a solar-type cycle, sector structure and preferential longitudes, starspot lifetimes, and the many observational manifestations of magnetic cycles.

Type
Part IV Stellar activity
Information
International Astronomical Union Colloquium , Volume 130: The Sun and Cool Stars: activity, magnetism, dynamos , 1991 , pp. 353 - 369
Copyright
Copyright © Springer-Verlag 1991

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