TU Bootis: An ambiguous W Ursae Majoris system

¹ Section of Astrophysics, Department of Physics, University of Athens, Panepistimiopolis, GR-15783 Zographos, Athens, Greece
² Alter Weg 7, D-54570 Weidenbach, Germany
³ Astronomisches Institut, Wilhelm-Klemm-Str. 10, D-48149 Münster, Germany

Send offprint request to: P.G. Niarchos

Received: 20 January 1995
Accepted: 11 November 1995

Abstract

The W UMa system TU Boo has a period of 0.32438 days and a spectral type G3. We present here the first photometric analysis, based on photoelectric B and V light curves. The q-search method was used to find the preliminary range of the mass-ratio in order to search for the final solution. The unspotted solution was found by using the unperturbed part of the light curve and applying the DC program of the WD code. Spot models were computed, a one-spot model to explain the O'Connell effect ( fainter than ) by introducing a cool spot on the larger component, and a two-spot model to explain both the O'Connell effect and the small excess of light just after by assuming, in addition, a bright region on the smaller component near the neck region of the common envelope. TU Boo is an A-type W UMa system with complete eclipses, the secondary minimum being an occultation. However, the derived physical parameters of the system and its light curve anomalies are more common for slightly evolved W-type systems.