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A&A Supplement Series, Vol. 125, October I 1997, 11-63

Received September 23; accepted December 16, 1996

Starspot photometry with robotic telescopes

Continuous UBV and tex2html_wrap_inline3957 photometry of 23 stars in 1991-1996

K.G. Strassmeiertex2html_wrap3977 - J. Bartustex2html_wrap3979 - G. Cutispototex2html_wrap3981 - M. Rodonótex2html_wrap3981

tex2html_wrap3985  Institut für Astronomie, Universität Wien, Türkenschanzstraße 17, A-1180 Wien, Austria
tex2html_wrap3987  Konkoly Observatory, Hungarian Academy of Sciences, H-1525 Budapest, Hungary
tex2html_wrap3989  Catania Astrophysical Observatory, V.le A. Doria 6, I-95125 Catania, Italy,


We report on the progress of our ongoing photometric monitoring program of spotted late-type stars with automatic photoelectric telescopes (APTs) on Mt. Hopkins in Arizona and on Mt. Etna in Sicily. We present 9250 differential UBV and/or tex2html_wrap_inline3957 observations for altogether 23 chromospherically active stars, singles and binaries, pre main sequence and post main sequence, taken between 1991 and 1996. The variability mechanism of our target stars is mostly rotational modulation by an asymmetrically spotted stellar surface. Therefore, precise rotational periods and their seasonal variations are determined using baselines between 3 years for HD 129333 to 34 years for V410 Tauri. We report the largest V light-curve amplitude of any spotted star observed to date: tex2html_wrap_inline3965 for V410 Tau in 1994-95. Long-term variations of the overall light levels of our target stars are sometimes of similar amplitude as the rotational modulation itself and are most likely caused by an analog of the solar 11-year spot cycle but mostly without a well-defined periodicity. For some of our target stars (HD 12545, HD 17433, EI Eri, V410 Tau, LQ Hya, and HD 106225) we estimate a probable cycle period. A complete light curve of the semi-regular S-type giant HR Pegasii is presented. All data are available via the WorldWideWebgif.

keywords: stars: activity -- stars: late-type -- stars: rotation -- binaries: spectroscopic -- techniques: photometric

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