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Abteilung Astronomie

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Preprint 04b/97

Analyzing short-term X-ray variability of Cygnus X-1 - Application of Linear State Space Models

Katja Pottschmidt and Michael König

Institut für Astronomie und Astrophysik, Astronomie, Universität Tübingen, Waldhäuser Str. 64, D-72076 Tübingen, Germany

Contribution to the Florence and George Wise Observatory 25th Anniverary Symposium on Astronomical Time Series, Tel Aviv, Israel, December 30, 1996 - January 1, 1997

Abstract. Cyg X-1 exhibits X-ray variability on all measured time scales. The observed short-term behaviour is usually described by shot noise models, which assume that the lightcurve is produced by superposition of randomly occuring shots. A more general approach is to analyse the X-ray variability by Linear State Space Models (LSSMs) which are based on the idea that the lightcurve can be modeled by an autoregressive process covered by observational noise. We have reanalysed EXOSAT ME observations of Cyg X-1 using Fourier techniques and LSSMs to describe the variability. The LSSM fits suggest the presence of a single relaxation time scale of ~0.2 s in the lightcurves.

Paper (147k gzip'ed Postscript including figures)

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