Non-LTE line formation for iron group elements.

Abstract

A non-LTE line formation calculation for Fe v is introduced. The data for radiative bound-bound transitions which have been derived as part of this work are described and their accuracy is evaluated. The theoretical non-LTE spectrum of Fe v is compared to the HST spectrum of the sdO star BD + 75 deg 325 resulting in a determination of the iron abundance. It is shown that a microturbulent velocity of no more than 5 km/s is needed to match the observations and that the value of 30 km/s as postulated by Hubeny et al. (1991) from an LTE analysis is an artifact of the LTE approximation.