Long-term monitoring of active stars. V. photometry collected in Feb.-Mar. 1990^*

Osservatorio Astrofisico di Catania, V.le A.Doria 6, I-95125 Catania, Italy e-mail: gcutispoto@astrct.ct.astro.it

Send offprint request to: G. Cutispoto

Received: 5 February 1996
Accepted: 5 March 1996

Abstract

High-precision UBV(RI)_c photometry of 12 selected active stars, collected at the European Southern Observatory (La Silla, Chile) over the period February - March 1990, is presented. Significant evolution of the light curves, period variations and, in most cases, evidence for long-term variability of the global degree of spottedness are found. Some of the spectral classifications are discussed. This paper is part of a more extensive program focusing on the global properties and evolution of active stars and is aimed at establishing a time-extended photometric database which can give important clues on topics such as the stability of the spotted areas, differential rotation and solar-like cycles.