Interstellar abundances in the Magellanic Clouds .1. GHRS observations of the Small Magellanic Cloud star Sk 108

We present HST GHRS echelle-B and G160M spectra of the Wolf-Rayet binary Sk 108, located in the northeastern part of the main ''bar'' of the Small Magellanic Cloud. The spectra show interstellar absorption from C I, O I, Si II, Si II*, S II, P II, Cr II, Mn II, Fe II, Ni II, and Zn II. We find at least 25 interstellar components, which may be grouped via similar kinematics and/or similar relative heavy element abundances into two sets arising in the Galactic disk and halo, plus three sets located in the SMC. The SMC component groups may correspond to large-scale SMC gas complexes identified in H I 21 cm emission surveys. The relative gas phase abundances for Si II, Cr II, Mn II, Fe II, Ni II, and Zn II found for the SMC interstellar components are similar to those found for interstellar clouds in the Galactic halo. Since the relative total abundances for those elements found for F-G supergiants and gaseous nebulae in the SMC are similar to those present in comparable Galactic objects, we conclude that the interstellar depletion patterns are also similar in the SMC and in the Galactic halo clouds, despite the significantly lower metallicity and dust-to-gas ratio in the SMC. We do not see the distinctive depletion patterns commonly found for cold and warm clouds in the Galactic disk for any of the SMC components along the line of sight to Sk 108. We discuss some implications of these results for understanding the abundances found for QSO absorption-line systems and conclude that both nucleosynthetic and depletion effects contribute to the observed abundances-to different degrees for different systems.