A&A Supplement Series, Vol. 125, October I 1997, 11-63
Received September 23; accepted December 16, 1996
photometry of 23 stars in 1991-1996K.G. Strassmeier
- J. Bartus
- G. Cutispoto
- M. Rodonó
Institut für Astronomie, Universität Wien,
Türkenschanzstraße 17, A-1180 Wien, Austria
Konkoly Observatory, Hungarian Academy of Sciences, H-1525 Budapest, Hungary
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 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:
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 WorldWideWeb
.
keywords: stars: activity -- stars: late-type -- stars: rotation -- binaries: spectroscopic -- techniques: photometric