Measurement of Mass and Spin of Black Holes with QPOs

There are now four low mass X-ray binaries with black holes which show twin resonant-like HFQPOs. Similar QPOs might have been found in Sgr A∗. I review the power spectral density distributions of the three X-ray flares and the six NIR flares published for Sgr A∗ so far, in order to look for more similarities than just the frequencies between the microquasar black holes and Sgr A∗. The three X-ray flares of Sgr A∗ are re-analysed in an identical way and white noise probabilities from their power density distributions are given for the periods reported around ∼ 1100 s. Progress of the resonant theory using the anomalous orbital velocity effect is summarized.