Implementing TOPbase/Iron Project: Continuous Absorption from Fe II
Abstract
We discuss implementation of TOPbase and Iron Project opacities for stellar spectral codes. We use a technique employed by Peach, where a Boltzmann-averaged cross section is calculated for selected temperatures, and the opacity obtained from double interpolation in temperature and wavelength. It is straightforward to include all levels for which cross sections have been calculated. Boltzmann-averaged cross sections for Fe II show a local maximum between 1700 and 2000[A]. We suggest this feature arises from 3d5 4snl to 3d5 4pnl transitions within Fe II. IUE spectra of iron-rich CP stars show local minima in this region. Theoretical calculations of a representative stellar continuum demonstrate that Fe II photoionization contributes significantly to the observed minima.
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