  We have observed the broad-line radio galaxy Arp 102B with ASCA in order to
determine the absorbing column density towards its X-ray source and measure its
X-ray spectrum. The ultimate goal was to constrain the properties of the medium
responsible for the metastable Fe II absorption lines observed in its UV
spectrum. The 0.5-10 keV X-ray spectrum is described by a simple power-law
model of photon index 1.58+/-0.04 modified by photoelectric absorption with an
column density of (2.8+/-0.3)x10^{21} cm^{-2}. An Fe K-alpha line is not
detected with an upper limit to its equivalent width of 200 eV (assuming FWHM =
60,000 km/s. Using the above column density the observed S.E.D. as constraints,
we explore simple photoionization models for the absorber for a wide range of
densities and ionization parameters in an effort to reproduce the strengths of
the UV absorption lines. We find that densities of at least 1x10^{11} cm^{-3}
are needed. However, a single ionization parameter cannot explain all of the
observed lines. An ionization parameter between 10^{-2.5} and 10^{-3.5} is
needed for the Mg and Fe lines and the soft X-ray absorption, but lines from
Si, C, Al, and H require different density-ionization parameter combinations.
According to the models, such an absorbing medium must be located very close to
the source of ionizing radiation (within 5,000 gravitational radii) and must be
very compact. As such, the properties of this absorbing medium differ from
those of more luminous quasars, but are reminiscent of the absorber in the
Seyfert galaxy NGC 4151. We suggest that the absorber is in the form of thin
sheets or filaments embedded in a wind wind that overlays the accretion disk of
Arp 102B. This picture is consistent with all of the available constraints on
the central engine of this object.
