EDP Sciences
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Volume 389, Number 1, July I 2002
Page(s) 202 - 212
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361:20020506

A&A 389, 202-212 (2002)
DOI: 10.1051/0004-6361:20020506

Doppler imaging of stellar surface structure

XVIII. The very active RS CVn binary UZ Librae revisited
K. Oláh1, K. G. Strassmeier2 and M. Weber2

1  Konkoly Observatory of the Hungarian Academy of Sciences, 1525 Budapest, Hungary
    e-mail: olah@konkoly.hu
2  Astrophysical Institute Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany

(Received 7 December 2001 / Accepted 3 April 2002)

We present eight Doppler images of UZ Librae from the years 1994, 1996, 1997, 1998 and 2000. These maps indicate a preferred temperature distribution from one year to the other and suggest preferred spot locations for at least the seven years of our observations. Two equatorial active regions appear facing towards and opposite the (unseen) companion star. A large and cool polar spot, with two or maybe three appendages extending down to a latitude of 40°-50°, is present and causes the long-term light variability of UZ Lib. The appendages appear at longitudes very similar to the two equatorial active regions and sometimes are possibly even attached to them. No coherent sign of differential rotation is found for the equatorial regions up to a latitude of approximately +50°, but the polar appendages may indicate a general acceleration of the polar regions. If interpreted as being due to differential rotation, if real at all, then UZ Lib clearly exhibits a non-solar flow pattern.

Key words: starspots -- stars: activity -- stars: atmospheres -- stars: late-type -- stars: individual: UZ Lib -- stars: binaries: close

Offprint request: K. G. Strassmeier, Kstrassmeier@aip.de, Mweber@aip.de

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