Evolution of the Precursor of SN1987A

Abstract

The evolution of a 17.5 M⊙ star, chosen to be similar to the precursor of SN1987A, has been studied using the input physics described in Wood and Faulkner (1987). The calculations: use opacities from the Astrophysical Opacity Library of Huebner et al (1977) with H, He, C, N, O and other metals in LMC ratios; treat semi-convection in the manner of Lamb, Iben and Howard (1976); and assume the mass loss rate to be the minimum of (a) α times the rate give in Waldron (1985) (this rate applied in the blue part of the HR diagram), and (b) L/(cv) (this rate applied in the red), where v is the stellar wind expansion velocity which was taken to be 12 km s−1.Typical evolutionary tracks resulting from these calculations are shown in Figure 1. The track shown as a continuous line is the one shown in Wood and Faulkner (1987) and corresponds to α = 2.5, while the track shown as a dotted line results from a slightly different treatment of semi-convection on the main-sequence and to α = 1.