Abundances of the elements in sharp-lined early-type stars from IUE high-dispersion spectrograms. II. The nitrogen deficiency in mercury-manganese stars

We determine nitrogen abundances from co-added IUE high-dispersion SWP spec trograms of four HgMn stars and five normal or superficially normal main-se quence 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 discusse d 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.