Analysis of Late--time Light Curves of Type IIb, Ib and Ic Supernovae

J. Craig Wheeler, V. Johnson, A. Clocchiatti

Published 2014-11-21Version 1

The shape of the light curve peak of radioactive-powered core-collapse "stripped-envelope," supernovae constrains the ejecta mass, nickel mass, and kinetic energy by the brightness and diffusion time for a given opacity and observed expansion velocity. Late-time light curves give constraints on the same parameters, given the gamma-ray opacity. Previous work has shown that the principal light curve peaks for SN IIb with small amounts of hydrogen and for hydrogen/helium-deficient SN Ib/c are often rather similar near maximum light, suggesting similar ejecta masses and kinetic energies, but that late-time light curves show a wide dispersion, suggesting a dispersion in ejecta masses and kinetic energies. It was also shown that SN IIb and SN Ib/c can have very similar late-time light curves, but different ejecta velocities demanding significantly different ejecta masses and kinetic energies. We revisit these topics by collecting and analyzing well-sampled single color and quasi-bolometric light curves from the literature. We find that the late-time light curves of all stripped-envelope core collapse supernovae are heterogeneous. The peak behavior is a poor predictor of the late-time light curve. The values for ejecta mass and energy derived from the peak nearly always predict too steep a late-time decline. The physics of the late-time light curves is fairly simple, so the discrepancies may lie in the physics of the peak. These discrepancies may point the way to asymmetries on small or large scales that alter the gamma-ray deposition near peak light or to time-dependent optical opacities that are not captured in simple models.