Mon. Not. R. Astron. Soc., 383, 741-749 (2008/January-2)
High-frequency X-ray variability as a mass estimator of stellar and supermassive black holes.
GIERLINSKI M., NIKOLAJUK M. and CZERNY B.
Abstract (from CDS):
There is increasing evidence that supermassive black holes in active galactic nuclei (AGN) are scaled-up versions of Galactic black holes. We show that the amplitude of high-frequency X-ray variability in the hard spectral state is inversely proportional to the black hole mass over eight orders of magnitude. We have analysed all available hard-state data from RXTE of seven Galactic black holes. Their power density spectra change dramatically from observation to observation, except for the high-frequency (≳10 Hz) tail, which seems to have a universal shape, roughly represented by a power law of index -2. The amplitude of the tail, CM(extrapolated to 1 Hz), remains approximately constant for a given source, regardless of the luminosity, unlike the break or quasi-periodic oscillation frequencies, which are usually strongly correlated with luminosity. Comparison with a moderate-luminosity sample of AGN shows that the amplitude of the tail is a simple function of black hole mass, CM= C/M, where C ~ 1.25M☉/Hz. This makes CMa robust estimator of the black hole mass which is easy to apply to low- to moderate-luminosity supermassive black holes. The high-frequency tail with its universal shape is an invariant feature of a black hole and, possibly, an imprint of the last stable orbit.
2007 The Authors. Journal compilation © 2007 RAS
accretion, accretion discs - galaxies: active - X-rays: binaries
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