In this paper we have presented a precise determination of absolute
parameters for the two components of the binary ZZ UMa, based on the first
light curves of this system combined with recent spectroscopic
determination of mass ratio.
For the cleaning of the light curve of intrinsic stellar activity, we have implemented a new iterative approach used first in the analysis of the high variable binary system BH Vir. Filling factors of 0.04 have been obtained from the activity wave analysis, that also indicate a complex geometry with at least two activity centres over the stellar surface. Due to the fact that we have mixed points from eight different observing runs, the above to referred activity centres could be a consequence of the superposition of different "instantaneous" waves more than of a real surface twin centre.
The geometric and photometric results obtained led us to conclude that ZZ UMa is composed of two main sequence stars of spectral type G0 and G5, with masses, radii and chemical compositions comparable to the Sun, that undergo total eclipse at secondary minimum.
The accuracy reached, in the determination of absolute parameters, is good enough to include ZZ UMa in the group of late-type binaries that can be used to improve the Mass-Luminosity Relationship at the end of the main sequence.
Acknowledgements
The 1.5 m telescope at Calar Alto is operated by the Observatorio Astronómico Nacional. We want to express our gratitude to the observatory staff. This work has been supported by the Spanish Comisión Interministerial de Ciencia y Tecnologıa (PB90-0001-C02).