Quasiperiodic Oscillations in Bright Galactic X-Ray Sources - Preliminary Results from Recent EXOSAT Observations

The author presents preliminary results of a series of EXOSAT observations of bright galactic X-ray sources carried out between 1985 August 28 and September 23 which led to the discovery of fast (2 - 30 Hz) quasi-periodic oscillations (QPO) in GX 17+2 and 4U1820-30, confirmed the presence of QPO in GX 349+2 and revealed a series of very interesting new features in the QPO from Rapid Burster (MXB 1730-33), when the source was in its flat-topped type II bursting mode. These new results are compared with the properties of QPO in the other three galactic X-ray sources for which this type of fast activity has been found (GX 5-1, Sco X-1 and Cyg X-2) and a classification scheme is proposed.