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Institut für Astronomie und Astrophysik

Abteilung Astronomie

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Preprint 11b/98

Temporal Properties of Cygnus X­1

Katja Pottschmidt (1) , Jörn Wilms (1) , Michael A. Nowak (2) , James B. Dove (2) , Mitchell C. Begelman (2) , Rüdiger Staubert (1)

(1) Institut für Astronomie und Astrophysik, Astronomie, Universität Tübingen, Waldhäuser Str. 64, D-72076 Tübingen, Germany
(2) JILA, University of Colorado, Boulder, CO, USA

3rd Integral Symposium - The Extreme Universe, in press

Abstract. We compare observational results from two RXTE observations of the black hole candidate Cygnus X-1 performed in 1996 October and 1997 December. The observations have the same intrinsic flux, but the second observation was made during a considerably harder spectral state and shows evidence for reprocessing of radiation in cold material.

We present results from Fourier timing techniques (power spectral densities and time lags). See Nowak et al. (1999) for a self-contained introduction to these methods. We verify the Belloni and Hasinger (1990) effect of a variable break frequency in the PSD. The cross energy analysis shows that the shape of the time lag can differ substantially between hard state observations of the same intrinsic luminosity.

Key words: -

Paper (69k gzip'ed Postscript including figures)

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Jürgen Barnstedt (barnstedt AT astro.uni-tuebingen.de)
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