Evolution of the precursor of SN 1987A.

Evolutionary calculations have been made for a star of initial mass 17.5 solar masses in order to emulate the evolution of the precursor of SN1987A. The results give good agreement with the observed properties of Sanduleak -69 deg 202 (star 1) when the model reaches the supernova epoch, and with the observed distribution of red and blue supergiants in the LMC. Mass loss throughout the life of the star at rates reasonably consistent with observed values is required to produce these results. At the time of explosion, the supernova has a mass of only about 5.4 solar masses and is surrounded by about 8 solar masses of wind material in a shell of about 0.4-pc radius.