Gamma-Ray Spectral Variability of Cygnus X-1

M. L. McConnell; K. Bennett; H. Bloemen; W. Collmar; W. Hermsen; L. Kuiper; W. Paciesas; B. Phlips; J. Poutanen; J. M. Ryan; V. Schoenfelder; H. Steinle; A. W. Strong; A. A. Zdziarski

doi:10.1063/1.1419379

arXiv · astro-ph/0106045

Gamma-Ray Spectral Variability of Cygnus X-1

M. L. McConnell·K. Bennett·H. Bloemen·W. Collmar·W. Hermsen·L. Kuiper·W. Paciesas·B. Phlips·J. Poutanen·J. M. Ryan·V. Schoenfelder·H. Steinle·A. W. Strong·A. A. Zdziarski

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Abstract

We have used observations from CGRO to study the variation in the MeV emission of Cygnus X-1 between its low and high X-ray states. These data provide a measurement of the spectral variability above 1 MeV. The high state MeV spectrum is found to be much harder than that of the low state MeV spectrum. In particular, the power-law emission seen at hard X-ray energies in the high state spectrum (with a photon spectral index of 2.6) is found to extend out to at least 5 MeV, with no evidence for any cutoff. Here we present the data and describe our efforts to model both the low state and high state spectra using a hybrid thermal/nonthermal model in which the emission results from the Comptonization of an electron population that consists of both a thermal and nonthermal component.

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M. L. McConnell, K. Bennett, H. Bloemen, W. Collmar, W. Hermsen, L. Kuiper, W. Paciesas, B. Phlips, J. Poutanen, J. M. Ryan, V. Schoenfelder, H. Steinle, A. W. Strong, A. A. Zdziarski. 2001-06-04. Gamma-Ray Spectral Variability of Cygnus X-1. https://doi.org/10.1063/1.1419379

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