Correlations of Power-law Spectral and QPO Features In Black Hole   Candidate Sources
  Recent studies have shown that strong correlations are observed between low frequency QPO`s and the spectral power law index for a number of black hole candidate sources (BHC's), when these sources exhibit quasi-steady hard x-ray emission states. The dominant long standing interpretation of QPO's is that they are produced in and are the signature of the thermal accretion disk. Paradoxically, strong QPO`s are present even in the cases where the thermal component is negligible. We present a model which identifies the origin of the QPO's and relates them directly to the properties of a compact coronal region which is bounded by the adjustment from Keplerian to sub-Keplerian inflow into the BH and which is primarily responsible for the observed power law spectrum. The model also predicts the relationship between high and low frequency QPO's and shows how BH's can be unique identified from observations of the soft states of NS's and BHC's. 
Ralph Fiorito,(Catholic University of America/NASA-GSFC), Lev   Titarchuk (George Mason University/Naval Research Laboratory)