X-ray reflected spectra from accretion disk models. I. Constant density
  atmospheres
  We present new models for illuminated accretion disks, their structure and
reprocessed emission. We consider the effects of incident X-rays on the surface
of an accretion disk by solving simultaneously the equations of radiative
transfer, energy balance and ionization equilibrium over a large range of
column densities. We assume plane-parallel geometry and azimuthal symmetry,
such that each calculation corresponds to a ring at a given distance from the
central object. Our models include recent and complete atomic data for K-shell
processes of the iron and oxygen isonuclear sequences. We examine the effect on
the spectrum of fluorescent K$\alpha$ line emission and absorption in the
emitted spectrum. We also explore the dependence of the spectrum on the
strength of the incident X-rays and other input parameters, and discuss the
importance of Comptonization on the emitted spectrum.
