Supernova SN 1961v: An explosion of a very massive star

Abstract

An investigation of the outburst of the unique supernova SN 1961v in the galaxy NGC 1058 is carried out. An analysis of hydrodynamic models of supernova outbursts and a comparison with a considerable body of observational data on SN 1961v clearly show that the SN 1961v phenomenon is an explosion of a very massive star (VMS) of a mass of 2000M ⊙ and a radius of about 100R ⊙ which results in expelling the envelope with a kinetic energy of 1.8×1052 erg. The light curve of SN 1961v (Figures 1, 7a, and 7b) furnishes direct evidence for the heterogeneity of the presupernova interior. The chemical composition profile produced during the evolution of the VMS and in the final explosion must have a number of the essential features (Figure 11). In particular, hydrogen has to be underabundant relative to the solar content and distributed in a specific manner throughout the star. At the late stages from February, 1963 to February, 1967, the light curve of SN 1961v (Figure 1) may be accounted for by the interaction of the expelled envelope with the stellar wind of the presupernova. The latest observations of SN 1961v in 1968 and 1970 are virtually those of a giantHii region created by the VMS before the explosion. Two astrophysical phenomena-the peculiar outburst of SN 1961v and the most luminous object R136a in the Large Magellacnic Cloud (LMC) which reveals a striking similarity with the presupernova-are evidence for the existence of VMSs. The evolution of VMSs similar to the object R136a may be terminated by explosions like the outburst of SN 1961v. Such explosions give rise to the formation of energetic supernova remnants whose examples may be the Cygnus superbubble and the supergiant shells in the LMC. A comparison of the internal structure of the presupernova with the available evolutionary calculations allows one to conclude that the influence of mass loss on the evolution of VMSs is negligible.