*Astron. Astrophys. 334, 201-209 (1998)*
## Analyzing short-term X-ray variability of Cygnus X-1
with Linear State Space Models
**
Katja Pottschmidt ,
Michael König ,
Jörn Wilms and
Rüdiger Staubert
**
Institut für Astronomie und Astrophysik, Astronomie,
University of Tübingen, Waldhäuser Strasse 64, D-72076
Tübingen, Germany
*Received 7 October 1997 / Accepted 13 February 1998*
**Abstract**
Cyg X-1 exhibits irregular X-ray variability on all measured
timescales. The usually applied shot noise models describe the typical
short-term behavior of this source by superposition of randomly
occuring shots with a distribution of shot durations. We have
reanalyzed EXOSAT ME observations of Cyg X-1 using the more
general Linear State Space Models (LSSMs). These models, which
explicitly take the observation-noise into account, model the
intrinsic system variability with an autoregressive (AR) process. Our
fits show that an AR process of first order can reproduce the system
variability of Cyg X-1. A possible interpretation is again the
superposition of individual shots, but with a single relaxation time
. This parameter was found to be 0.19 s.
**Key words:** X-rays:
stars
binaries: close
accretion, accretion
disks
stars: individual:
Cyg X-1
methods: statistical
*Send offprint requests to:* K. Pottschmidt, (katja@astro.uni-tuebingen.de)
SIMBAD Objects
### Contents
© European Southern Observatory (ESO) 1998
Online publication: May 12, 1998
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