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Preprint 05a/02

Short term X-ray rms variability of Cyg X-1

T. Gleissner (1), J. Wilms (1), K. Pottschmidt (2,3), P. Uttley (4), M.A. Nowak (5) and R. Staubert (1)

(1) Institut für Astronomie und Astrophysik, Astronomie, Universität Tübingen, Sand 1, D-72076 Tübingen, Germany
(2) Max-Planck-Institut für extraterr. Physik, Postfach 1312, 85748 Garching, Germany
(3) INTEGRAL Science Data Center, 16, Chemin d'Ecogia, 1290 Versoix, Switzerland
(4) Department of Physics and Astronomy, University of Southampton, Southampton S017 1BJ, UK
(5) MIT-CXC, NE80-6077, 77 Massachusetts Ave., Cambridge, MA 02139, USA

To appear in: Proceedings of the 4^th Microquasar Workshop, eds. Ph Durouchoux, Y. Fuchs and J. Rodriguez, published by the Center for Space Physics: Kolkata

Abstract. A linear dependence of the amplitude of broadband noise variability on flux for GBHC and AGN has been recently shown by Uttley & McHardy. We present the long term evolution of this rms-flux-relation for Cyg X-1 as monitored from 1998-2002 with RXTE. We confirm the linear relationship in the hard state and analyze the evolution of the correlation for the period of 1996-2002. In the intermediate and the soft state, we find considerable deviations from the otherwise linear relationship. A possible explanation for the rms-flux-relation is a superposition of local mass accretion rate variations.

Key words: -

Paper (73k gzip'ed Postscript including figures)

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