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Astron. Astrophys. 343, 33-40 (1999) AcknowledgementsWe are grateful to G. Palumbo for critical reading of the manuscript. We would like to thank T. Yaqoob, W. Wamsteker for useful discussions, and L. Angelini for help in reducing the archival EXOSAT data. We wish to thank the referee for useful comments on the manuscript. ![]() ![]() ![]() ![]() © European Southern Observatory (ESO) 1999 Online publication: March 1, 1999 ![]() |