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U.J. Sofia (Whitman Coll.), D.M. Meyer (Northwestern U.)
It is difficult to determine the composition of the interstellar medium (ISM) because a large fraction of some metals are in the solid form (dust). For this reason, stellar abundances (mostly solar and/or B stars) are often adopted to represent the ISM composition. These stellar abundances, however, have not been completely satisfying because they have led to incompatibilities with interstellar grain theories. Recent work on solar and stellar abundances has prompted us to reevaluate the compositions of stars versus the ISM. We compare previously published abundances for B stars, young (\leq2 Gyr) later-type (F and G) stars and the Sun to the modeled dust- and measured gas-phase compositions of the interstellar medium. Abundances for the five most populous elements in dust grains, C, O, Mg, Si and Fe, and the cosmically abundant element, N are used for this analysis. B stars have measured metal abundances that are, in most cases, substantially lower than the later type stars and the Sun. These low abundances are incompatible with the composition of the interstellar medium. Young F and G disk stars and the Sun, however, agree quite well with each other and neither can be ruled out as a reliable proxy for the ISM composition. Each of these 2 abundance standards agrees well with both interstellar theory and measurements.