A search for solar-like oscillations in the stars of M67 with CCD ensemble photometry on a network of 4 m telescopes

Results are presented from a large observational project directed toward the detection of solar-like oscillations in an ensemble of open cluster stars. Seven groups collaborated in 1992 January to observe twelve stars in M67 with 4 m class telescopes for a one week period. High quality time series were collected on 22 telescope nights for a total of 156 h. The technique of CCD ensemble photometry allowed precisions of about 250 μmag per minute to be reached in the best cases, and provided robust results in conditions that sometimes were far from photometric. The longitude-distributed network, coupled with generally low noise levels, provided a good window function and yielded detection thresholds of about 20 μmag (five times solar) for solar-like oscillations in the best ensemble stars