Explosion of a blue supergiant: a model for supernova SN1987A

Abstract

We present a model for the outburst of supernova SN1987A. This supernova was discovered in the Large Magellanic Cloud on 24 February, 1987. Astrometry^1,2 reveals the supernova to lie within 0.1 arcs of the B3 I supergiant Sanduleak (Sk) –69 202. The optical features indicate that the event was a type II supernova. Such supernovae are the expected consequence of the evolution of massive stars M >=10M⊙ and may be expected to leave behind a neutron star or black-hole remnant. Neutrinos released as a consequence of the anticipated core collapse to neutron star densities may indeed have been observed (ref. 3; Aglietta et al. preprint, 1987; Bionta et al. preprint, 1987). SN1987A certainly cannot be considered a prototype of a type II supernova, however, as it has proved to be unusual in several respects, including: (1) the progenitor of SN1987A appears to have been a blue supergiant rather than a red supergiant star; (2) SN1987A was found to be some 3 or 5 magnitudes dimmer at visual maximum than is known to be typical of supernovae of type II; and (3) SN1987A exhibited an extremely rapid spectral development, seemingly consistent with the very high expansion velocities inferred from studies of the hydrogen absorption features in the early spectra. Here we present a model for the outburst of SN1987A that permits a straightforward interpretation of the observed behaviour.