Gamma-ray spectral variability of Cygnus X-1

Academic Article


  • 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.
  • Authors

  • McConnell, Mark
  • Bennett, K
  • Bloemen, H
  • Collmar, W
  • Hermsen, W
  • Kuiper, L
  • Paciesas, W
  • Phlips, B
  • Poutanen, J
  • Ryan, JM
  • Schonfelder, V
  • Steinle, H
  • Strong, AW
  • Zdziarski, AA
  • Status

    Publication Date

  • 2001
  • Published In


  • astro-ph
  • Digital Object Identifier (doi)

    Start Page

  • 96
  • End Page

  • 100
  • Volume

  • 587
  • Issue

  • 1