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Study of FK Comae Berenices
II. Spot evolution from 1994 to 1997 *
H. Korhonen 1,
S.V. Berdyugina 1,
T. Hackman 2,
K.G. Strassmeier 3 and
I. Tuominen 1
Received 5 May 2000 / Accepted 5 July 2000
We present new surface (Doppler) images of the late-type single giant FK Com for June-July 1996, July-August 1996, April 1997 and June 1997. These images are compared with the previously published images from 1994 and 1995. The consecutive maps are cross-correlated to see the possible migration of the spots and the effects of differential rotation. The cross-correlation confirms an average longitudinal spot migration of in phase within a year. This movement is probably an artifact caused by a difference between the accepted rotation period and the real photometric period for these years. If this is true, then the photometric rotation period for these years is . Measurements from these four years and six maps limit the surface differential rotation to , where is the difference between polar and equatorial angular velocities relative to the equatorial angular velocity.
Key words: stars: activity stars: imaging stars: individual: FK Comae stars: late-type stars: starspots
* Based on the observations obtained at the Nordic Optical Telescope, Observatorio Roque de los Muchachos, La Palma, Canary Islands, Spain; the National Astronomical Observatory, Rozhen, Bulgaria; the Kitt Peak National Observatory, USA; the Automatic Photometric Telescope, Phoenix 10, Arizona, USA.
Send offprint requests to: H. Korhonen (email@example.com)
Online publication: August 23, 2000