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.
