A NEW SCHEME FOR MULTIDIMENSIONAL LINE TRANSFER .2. ETLA METHOD IN ONE DIMENSION WITH APPLICATION TO IRON K-ALPHA LINES

The one-dimensional version of the radiation hydrodynamics computer code ALTAIR is described. It is an implementation of the equivalent two-level atom method, and also incorporates a variety of other iterative techniques to achieve a fast, accurate solution of the problem of coupled atomic kinetics and radiative transfer. All the techniques are described in sufficient detail to enable their use by others. The application of the program is illustrated by a set of calculations of the iron X-ray emission spectrum from intercloud hot gas that may exist in the broad-line region of active galactic nuclei. These calculations demonstrate that such spectra may be a rich lode to mine for information about the hot gas in AGNs, and also that the concept of "the iron, K-alpha line" inadequately depicts the spectrum.