Hubble Space Telescope observations of oxygen-rich supernova remnants in the Magellanic Clouds. II. Elemental abundances in N132D and 1E 0102.2-7219

We present Hubble Space Telescope (HST) Wide Field and Planetary Camera 2 i mages and Faint Object Spectrograph data of two young supernova remnants in the Magellanic Clouds, N132D (LMC) and 1E 0102.2-7219 (SMC). The spectra c over essentially the entire UV/optical range available to HST and provide t he first true comparison of UV/optical line intensities from astrophysical shocks that do not depend on scalings from different aperture sizes or inst ruments. For the spectra, we isolated specific knots and filaments that con tain fast-moving debris of nuclear-processed material that are devoid of hy drogen and appear to have originated from the cores of the progenitor stars . In N132D we also observed a knot on the outer rim of the remnant that rep resents a shocked interstellar cloud. In the debris from both remnants, we identify only the elements O, Ne, C, and Mg. We find no evidence for oxygen -burning products, such as S, Ca, Ar, etc., which are seen in Cas A and are expected from models of Type II supernovae. We suggest that the progenitor stars of N132D and 1E 0102.2-7219 had large, oxygen-rich mantles (perhaps Wolf-Rayet stars) and may be the products of Type Ib supernovae. Shock mode ling demonstrates systematic differences in the relative abundances in the O-rich debris, possibly pointing to different progenitor masses for these t wo objects. The shocked interstellar knot in N132D shows that we are probab ly seeing a range of conditions within the similar to 1 " aperture and that no evidence is present for enrichment by a precursor star wind.