  We report new spectral modeling of the accreting X-ray pulsar Hercules X- 1.
Our radiation-dominated radiative shock model is an implementation of the
analytic work of Becker & Wolff on Comptonized accretion flows onto magnetic
neutron stars. We obtain a good fit to the spin-phase averaged 4 to 78 keV
X-ray spectrum observed by the Nuclear Spectroscopic Telescope Array during a
main- on phase of the Her X-1 35-day accretion disk precession period. This
model allows us to estimate the accretion rate, the Comptonizing temperature of
the radiating plasma, the radius of the magnetic polar cap, and the average
scattering opacity parameters in the accretion column. This is in contrast to
previous phenomenological models that characterized the shape of the X-ray
spectrum but could not determine the physical parameters of the accretion flow.
We describe the spectral fitting details and discuss the interpretation of the
accretion flow physical parameters.

High Energy Astrophysical Phenomena