Close binary and other variable stars in the solar-age Galactic open cluster M 67^*

¹ Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
² University of Cambridge, Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK e-mail: yakut@ast.cam.ac.uk
³ University of Ege, Department of Astronomy & Space Sciences, 35100 Izmir, Turkey
⁴ Izmir Institute of Technology, Department of Physics, 35430 Izmir, Turkey
⁵ Royal Observatory of Belgium, Ringlaan 3, 1180 Brussel, Belgium
⁶ LPNHE – Université Paris, 75252 Paris Cedex 05, France
⁷ TÜBİTAK National Observatory, Antalya, Turkey
⁸ IMAPP, Radboud Universiteit Nijmegen, PO Box 9010, 6500 GL Nijmegen, The Netherlands

Received: 21 February 2009
Accepted: 5 June 2009

Abstract

We present multi-colour time-series CCD photometry of the solar-age galactic open cluster M 67 (NGC 2682). About 3600 frames spread over 28 nights were obtained with the 1.5 m Russian-Turkish and 1.2 m Mercator telescopes. High-precision observations of the close binary stars AH Cnc, EV Cnc, ES Cnc, the δ Scuti type systems EX Cnc and EW Cnc, and some long-period variables belonging to M 67 are presented. Three full multi-colour light curves of the overcontact binary AH Cnc were obtained during three observing seasons. Likewise we gathered three light curves of EV Cnc, an EB-type binary, and two light curves of ES Cnc, a blue straggler binary. Parts of the light change of long-term variables S1024, S1040, S1045, S1063, S1242, and S1264 are obtained. Period variation analysis of AH Cnc, EV Cnc, and ES Cnc were done using all times of mid-eclipse available in the literature and those obtained in this study. In addition, we analyzed multi-colour light curves of the close binaries and also determined new frequencies for the δ Scuti systems. The physical parameters of the close binary stars were determined with simultaneous solutions of multi-colour light and radial velocity curves. Finally we determined the distance of M 67 as 857(33) pc via binary star parameters, which is consistent with an independent method from earlier studies.