X-ray QPOs in Black-Hole Binary Systems

We briefly review the properties and physical consequences of quasiperiodic oscillations (QPOs) seen on many occasions in the X-ray emission from black-hole binary systems. We also report on the discovery of QPOs at 164 and 328 Hz in GRS1915+105. These appear to be analogous to the harmonic systems of high-frequency QPOs seen in XTEJ1550-564 and GROJ1655-40.