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W. B. Focke, E. D. Bloom, B. Giebels, G. Godfrey, Y. Jiang, P. Saz Parkinson, K. T. Reilly, G. Shabad, D. M. Tournear (Stanford Linear Accelerator Center, Stanford Univ.), K. S. Wood, R. M. Bandyopadhyay, G. Fritz, P. Hertz, M. P. Kowalski, M. N. Lovellette, P. S. Ray, M. T. Wolff, D. J. Yentis (E. O. Hurlbert Center for Space Research, NRL), J. D. Scargle (NASA/Ames)
Uttley & McHardy (MNRAS, 323, L26, 2001) demonstrated a simple new diagnostic of variability in accreting sources. It involves the relation of the RMS (absolute, not fractional) variability of the source to its luminosity. They observed a linear relation in a black hole candidate and a neutron star, and observed behavior consistent with such a relation in an active galactic nucleus.
We explore and expand on this diagnostic. The diagnostic is applied to data collected with ARGOS/USA and RXTE/PCA data for Cygnus~X-1 and other accretion powered X-ray sources. We find that a two-dimensional distribution is necessary to describe the data. We apply the diagnostic to model light curves to constrain models of the time variability of the sources.
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.