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Issue A&A Volume 374, Number 1, July IV 2001 Page(s) 171 - 181 Section Formation, structure and evolution of stars DOI 10.1051/0004-6361:20010682

A&A 374, 171-181 (2001)
DOI: 10.1051/0004-6361:20010682

Surface imaging of HD 199178 ( V1794 Cygni )

T. Hackman¹, L. Jetsu¹ and I. Tuominen<sup>2

1</sup>  Observatory, PO Box 14, 00014 University of Helsinki, Finland
²  Astronomy Division, PO Box 3000, 90014 University of Oulu, Finland

(Received 13 September 1999 / Accepted 10 May 2001 )

Abstract
We present surface temperature maps for the FK Comae-type star HD 199178 (V1794 Cygni) calculated from high resolution spectra obtained in 1994 and 1995. The spot pattern evolves, but all maps reveal a large cool spot remaining nearly at the same high latitude. The main spot is 1200-1600 K cooler than the mean surface temperature. The observed slightly flat bottomed absorption lines would usually be interpreted as evidence for a large cool polar spot. We argue that antisolar surface differential rotation offers a better explanation for the box like shape of the line profiles. However, we do not find conclusive evidence for antisolar differential rotation and note that there are still other possible explanations for the slightly flat bottomed line profiles.

Key words: stars: activity, imaging, late-type, starspots, individual: HD 199178

Offprint request: T. Hackman, Thomas.Hackman@Helsinki.Fi

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