Gamma-Ray Spectral Variability of Cygnus X-1

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...

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Veröffentlicht in:arXiv.org 2001-06
Hauptverfasser: McConnell, M L, Bennett, K, Bloemen, H, Collmar, W, Hermsen, W, Kuiper, L, Paciesas, W, Phlips, B, Poutanen, J, Ryan, J M, Schoenfelder, V, Steinle, H, Strong, A W, Zdziarski, A A
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Sprache:eng
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Zusammenfassung: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.
ISSN:2331-8422
DOI:10.48550/arxiv.0106045