Four colour photometry of late-type binary systems^*,**

I. First light curves of ZZ Ursae Majoris

¹ Departamento de Astronomía y Astrofísica, Universidad de Valencia, Dr. Moliner 50, E-46100 Burjassot, Valencia, Spain
² Departamento de Física Aplicada, E.U.I.T. Industrial, Universidad Politécnica de Madrid, Ronda de Valencia 3, E-28012 Madrid, Spain
³ The Niels Bohr Institute for Astronomy, Physics and Geophysics, Astronomical Observatory, Brorfeldevej 23, DK-4340, Töllöse, Denmark

Send offprint request to: R. Clement

Received: 3 June 1996
Accepted: 13 September 1996

Abstract

This paper presents first complete uvby light curves of the late-type detached eclipsing binary ZZ UMa (, ). This binary system has been observed during eight campaigns at the Calar Alto Observatory (Almeria, Spain)and at the Sierra Nevada Observatory (Granada, Spain). 294 points distributed over the binary period and covering both eclipses are given. The comparison stars used to calculate the differential light curves (SAO 15242 and SAO 15251) were confirmed as being good reference stars with constant flux. These observations are part of a 6 year uvby and monitoring program of low mass eclipsing binaries whose main objective is to provide accurate absolute astrophysical parameters for late-type main sequence stars. Details about the standardisation process and accuracy of the photometry are also given. The internal accuracy of the standard photometry measured as the mean RMS of the differences between standard and observed values for the standard stars observed along the program is only a few millimagnitudes. Detailed analysis of ZZ UMa, based on these light curves, will be published separately.