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Understanding the long-term spectral variability of Cygnus X-1 with BATSE and ASM observations by Zdziarski, Andrzej A.; Poutanen, Juri; Paciesas, William S.; Wen, Linqing is a scholarly article available to read on EtoBox.

What is Understanding the long-term spectral variability of Cygnus X-1 with BATSE and ASM observations about?

We present an analysis of all observations of Cygnus X-1 by the BATSE (20-300 keV) and by ASM (1.5-12 keV) until 2002 June, including 1200 days of simultaneous data. We find a number of correlations between fluxes and hardnesses in different energy bands. In the hard state, the variability can be explained by softening the overall spectrum with a pivot at 50 keV and another, independent variability pattern where the spectral shape does not change when the luminosity changes. In the soft state, the variability is caused by a variable hard tail of a constant shape superimposed on a constant soft component. These variability patterns are in agreement with the energy-dependent rms variability in the two states. We also study in detail recent soft states in 2000-02. The last of them has lasted so far for >200 days. Their spectra are harder in the 1.5-5 keV band but similar or in the 3-12 keV band than those of the 1996 soft state whereas the rms variability is stronger in all the ASM bands. On the other hand, the 1994 soft state transition observed by BATSE appears very similar to the 1996 one. We interpret the variability patterns by theoretical Comptonization models. In the hard state

Author

Zdziarski, Andrzej A.; Poutanen, Juri; Paciesas, William S.; Wen, Linqing

Published

2002

Language

EN