Looking for binaries in old open clusters

We propose to observe the old open clusters NGC7142, NGC7789 and NGC3680. Basedon the ROSAT observation of M67, we expect to detect up to 10 Xray sources ineach cluster. Most of these will be interacting binaries but a hot white dwarfand/or a cataclysmic variable may also be detected. Interacting binaries in oldclusters are excellent test cases for the theory of binary evolution, in particular in relation to circularization and synchronization of the binaryorbit by tidal forces. Xray observations are an efficient way to identify suchinteracting binaries; furthermore, the detection of Xray sources in old openclusters is interesting for the comparison with Xray properties of globularclusters. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]