High-frequency quasi-periodic oscillations in black hole binaries

We present the results of the analysis of a large data base of X-ray observations of 22 galactic black hole transients with the Rossi X-Ray Timing Explorer throughout its operative life for a total exposure time of similar to 12 ms. We excluded persistent systems and the peculiar source GRS 1915+105, as well as the most recently discovered sources. The semi-automatic homogeneous analysis was aimed at the detection of high-frequency (1001000?Hz) quasi-periodic oscillations (QPO), of which several cases were previously reported in the literature. After taking into account the number of independent trials, we obtained 11 detections from two sources only: XTE J1550-564 and GRO J1655-40. For the former, the detected frequencies are clustered around 180? and 280?Hz, as previously found. For the latter, the previously reported dichotomy 300450?Hz is found to be less sharp. We discuss our results in comparison with kHz QPO in neutron-star X-ray binaries and the prospects for future timing X-ray missions.