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Astron. Astrophys. 346, 101-110 (1999)

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Study of FK Comae Berenices

I. Surface images for 1994 and 1995 *

H. Korhonen 1,3, S.V. Berdyugina 1, T. Hackman 2, R. Duemmler 1, I.V. Ilyin 1 and I. Tuominen 1

1 Astronomy Division, University of Oulu, P.O. Box 3000, FIN-90401 Oulu, Finland
2 Observatory, P.O. Box 14, University of Helsinki, FIN-00014 Helsinki, Finland
3 Nordic Optical Telescope, Apartado 474, E-38700 S/C de La Palma, Canarias, Spain

Received 2 September 1998 / Accepted 10 March 1999

Abstract

We present new surface images of FK Com for August 1994 and July 1995. For the 1995 images two different inversion methods, Tikhonov regularization and the Occamian approach, are used to check the dependence on the formal assumptions. The images are found to be very similar when the same local line profiles, models, stellar parameters and observations are used as inputs for both methods. The validity of the maps and their temperature scales are independently checked with photometric observations.

The maps for both years show active regions of very similar substructures and latitudes. It seems that the same spot group has survived on the surface of FK Com for the 11 months between the observations; however, during that time it has moved about 0.2 in phase. The movement and evolution of the spot groups seem to cause the photometrically observed "flip-flop" phenomenon, which is noticed to be repeated with an average period of 6.5 years, similar to some RS CVn-stars.

Key words: stars: activity – stars: imaging – stars: individual: FK Com – 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.

Send offprint requests to: H. Korhonen (heidi.korhonen@oulu.fi)

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© European Southern Observatory (ESO) 1999

Online publication: May 6, 1999
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