Abundances of the Elements in Sharp-lined Early-Type Stars from IUE High-Dispersion Spectrograms. II. The Nitrogen Deficiency in Mercury-Manganese Stars

摘要

We determine nitrogen abundances from co-added IUE high-dispersion SWP spectrograms of four HgMn stars and five normal or superficially normal main-sequence B and A stars. We find N deficiencies in the HgMn stars greater than previously reported (depletion factors of 135-400 relative to the Sun). N abundance discrepancies from UV and IR studies of normal stars are discussed in light of possible non-LTE effects. Our data set for our sample of HgMn stars (observed with a consistent strategy to maximize the benefits of co-additions) is an improvement over the single or few images previously used to derive N abundances for most of these stars.