THE CA-II EMISSION-LINES OF SN-1987A

We study the evolution of the [Ca II] lambdalambda7300 and Ca II lambdalambda8600 emission lines in the spectrum SN 1987A. We can explain the observations with a model in which (1) the lines come from approximately 1.7 x 10(-4) M. of calcium distributed with filling factor f(Ca) approximately 0.1 in a sphere expanding with velocity 2500 km s-1; (2) the electron number density is given by N(e) approximately 4 x 10(9) cm-3 (t/100 d)-3; (3) the gas temperature decreases from T almost-equal-to 6400 K at 200 days to T almost-equal-to 3900 K at 500 days and (4) ultraviolet pumping in the Ca II lambdalambda3934, 3969 (K, H) lines is required to explain the line ratios for t greater than or similar to 350 days. The mass of calcium in our model is consistent with the LMC abundance of calcium in approximately 5 M. of hydrogen in the inner envelope of SN 1987A. If more calcium is produced by supernova nucleosynthesis, it must be in dense clumps that are too cool (T less than or similar to 3000 K at 200 days) to emit the [Ca II] lambdalambda7300 and Ca II lambdalambda8600 lines.