Multi-site time series photometry of the open cluster M67

Early January 2004, a very ambitious multi-site campaign was launched. 22 astronomers using 9 telescopes distributed around the world were to observe as continuously as possible for 6 weeks. Their target was M67, one of the oldest known stellar open clusters. The primary goal was to detect solar-like oscillations in the cluster red giant stars, which was motivated by the very promising first clear detection of solar-like oscillations in the red giant star ξ Hya (Stello, 2002; Frandsen et al., 2002). Similar multi-site observations of M67 were conducted by Gilliland et al. (1993), but aimed at detecting solar-like oscillations in less luminous stars. As a spin-off, this huge observing campaign has furthermore provided extremely valuable time series photometry of high quality for several hundred stars in and around the cluster. These include different types of variable stars e.g. δ Scuti stars and eclipsing binaries. The brightest stars in the field show an internal noise in the time series of only 2 mmag per data point. This paper is a progress report on our M67 time series.