Chemical abundance in the SN 1987A ejecta

A simple model is considered for the region where the absorption features are formed in the spectrum of SN 1987A. Taking into account the proposed identifications for those features, we have estimated the heavy-element abundances in the reversing layer. The abundances are consistent with the actual LMC metallicity. From the forbidden oxygen lines we have estimated an ejected hydrogen-mass around 9 solar masses and a total envelope mass of around 14-15 solar masses if helium is enriched by 40 per cent with respect to the normal value. (author)