Cygnus X-1: shedding light on the spectral variability of a black hole





Citation of Original Publication

Grinberg, Victoria. “Cygnus X-1: Shedding Light on the Spectral Variability of a Black Hole.” In Proceedings of An INTEGRAL View of the High-Energy Sky (the First 10 Years) - 9th INTEGRAL Workshop and Celebration of the 10th Anniversary of the Launch — PoS(INTEGRAL 2012), 176:050. SISSA Medialab, 2013.


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The knowledge of the spectral state of a black hole is essential for the interpretation of data from black holes in terms of their emission models. Based on pointed observations of Cyg X-1 with the Rossi X-ray timing Explorer (RXTE) that are used to classify simultaneous RXTE-ASM observations, we develop a scheme based on RXTE-ASM colors and count rates that can be used to classify all observations of this canonical black hole that were performed between 1996 and 2011. We show that a simple count rate criterion, as used previously, leads to a significantly higher fraction of misclassified observations. This scheme enables us to classify single INTEGRALIBIS science windows and to obtain summed spectra for the soft, intermediate and hard state with low contamination by other states.