THEORETICAL LIGHT-CURVE OF SN-1987A AND MIXING OF HYDROGEN AND NICKEL IN THE EJECTA

Refined light curve models for SN 1987A are presented. Improvements are due to the presupernova models taken from the evolutionary calculations and the postexplosion abundance distribution in the ejecta as inferred from the X-ray and y-ray light curves. We have found the following effects of material mixing in the ejecta on the light curve shape. Radioactive materials mixed into the surface layer with the expansion velocity of ∼3000 km s-1 provide energy to increase the luminosity after ∼ day 25; this accounts for the observed light curve and the Bochum event. Mixing of hydrogen into the core shows a significant effect on the light curve, since the hydrogen recombination wave plays an essential role in forming a plateau-like peak of the light curve. The calculated plateau is broader if the minimum velocity of the hydrogen layer vminH is lower, i.e., if hydrogen is mixed into the deeper core. For vminH ∼ 800 km s-1, the calculated light curve is successful in reproducing the broad peak from ∼ day 60-100. With such mixing of hydrogen and 56Ni, the theoretical light curve is in good agreement with the observation if the ratio between the explosion energy and the mass of the hydrogen-rich envelope is E/Menv = (1.1 ± 0.3) × 5050 ergs M⊙-1. The light curves of other Type II supernovae are also discussed in terms of vminH.