X-RAY AND GAMMA-RAY EMISSION IN OPEN CLUSTERS

We have studied a number of galactic open clusters that lie in the err or boxes of COS B sources. These clusters belong to complexes in which similar star formation processes occur. They have similar ages, stell ar population and contain peculiar stars with very high-velocity stell ar winds. We propose that a system of shock fronts, set up at the inte rfaces between the hypersonic wind of the peculiar stars and the other cluster members, generates acceleration of cosmic ray particles, whos e interactions with the inter-cluster gas concentrations would be resp onsible for the observed gamma-ray emission. We find various observati onal evidences (including CGRO data, strongly supporting the associati on of the gamma-ray source J 2021+37=2CG075+00 with Berk 87) for the p resence of such shock fronts in some of these clusters. We show that t he diffuse hard X-ray emission from the clusters regions is consistent with the geometric scenario inferred from the data and with the assum ed mechanism of cosmic ray acceleration.