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Optical variability in the unusual K5 V infrared-excess star HD 98800
The dusty infrared-excess star HD 98800 (K5 V) was observed for severalweeks in the spring of 1993 by the Vanderbilt/Tennessee State 0.4 mautomatic photoelectric telescope. It was found to be a variable starwith an amplitude of 0.07 mag in V and a period of 14.7 days. We show,by comparison with other chromospherically active variable stars andconstant stars with good observational histories, that the Rossby numberfor HD 98800, determined to be 0.30, places it well within the regime ofstars whose convective envelopes and rotation rates combine to drive amagnetic dynamo strong enough to generate photometrically observablestarspots. The light curve suggests at least two large spots at somewhatdifferent longitudes on HD 98800, one of which could be as large as 16deg in radius.
| Hyades and Sirius supercluster members brighter than magnitude (V) 7.1. II - Right ascension six to twelve hours
The present star sample is contained in the Bright Star Catalogue andits Supplement, augmented with a further supplement of 788 stars foundduring various observing programs over the past 40 years. Accurate,four-color and H-beta, or (RI), photometry is available for most of thesupercluster members. The criteria for membership are the comparisons ofthe proper motion, radial velocity, and luminosity obtained from thesupercluster parameters with the observed motions and the luminosityderived from the photometric parameters. New proper motions, based onall available catalogs, have been derived for the additional 788 starsdiscussed here, as well as all supercluster members.
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