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Issue A&A Volume 371, Number 3, June I 2001 Page(s) 1024 - 1034 Section Formation, structure and evolution of stars DOI 10.1051/0004-6361:20010466

A&A 371, 1024-1034 (2001)
DOI: 10.1051/0004-6361:20010466

I. UBV photometry of selected members of the Pleiades and Alpha Persei clusters in 1999

S. Messina

Catania Astrophysical Observatory, via S. Sofia 78, 95125 Catania, Italy

(Received 8 September 2000 / Accepted 22 March 2001 )

Abstract
The rotational brightness variations in magnetically active stars are due to the combined light contribution of cool spots and bright faculae on the stellar photosphere. The amplitude of the rotational brightness variations can be used to probe the dependence of the amount of photospheric magnetic fields associated to such inhomogeneities on global stellar parameters such as the rotation rate. However, the upper envelope of the amplitude values must be considered, since the rotational modulation amplitude represents a lower limit of the spots and faculae coverage, being their visibility modulation reduced by several factors. In order to determine accurately the maximum amplitude upper envelope and its dependence on global stellar parameters a program of photometric monitoring of ultra fast rotating active members of the Pleiades and Alpha Persei star clusters was undertaken in the fall of 1999. Light curves and period determinations of 21 target stars are presented as result from the first observing season. The newly determined values of amplitudes of the brightness variations versus rotation period have values as expected based on previous results.

Key words: stars: late-type -- activity -- rotation -- starspots

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© ESO 2001

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