On the Low and High Frequency Correlation in Quasi-Periodic Oscillations Among White Dwarfs, Neutron Star and Black Hole Binaries

Abstract

We interpret the correlation over five orders of magnitude between high frequency and low frequency in a quasi-periodic oscillations (QPO) found by Psaltis, Belloni & van der Klis (1999) for black hole (BH), neutron star (NS) systems and then extended by Mauche (2002) to white dwarf (WD) binaries. We argue that the observed correlation is a natural consequence of the Keplerian disk flow adjustment to the innermost sub-Keplerian boundary conditions near the central object. In the framework of the transition layer model the high frequency is related to the Keplerian frequency at the outer (adjustment) radius and the low frequency is related to the magnetoacoustic oscillation (MA) frequency. Using a relation between the MA frequency the magnetic and gas pressure and the density and the hydrostatic equilibrium condition in the disk we infer a linear correlation the Keplerian frequency and the MA frequency. We estimate the magnetic field strength near the TL outer radius for BHs NSs and WDs. The fact that the observed high-low frequency correlation over five orders of magnitude is valid for BHs, NSs, and down to WDs strongly rules out relativistic models for QPO phenomena. We come to the conclusion that the QPOs observations indicate the adjustment of the geometrically thin disk to sub-Keplerian motion near the central object. This effect is a common feature for a wide class of systems, starting from white dwarf binaries up to black hole binaries.Comment: 8 pages, 1 figure, accepted for publication in the ApJ. Letters 2002 August