On the Light Curves of Stripped‐Envelope Supernovae

Representative light curves of supernovae of Types Ib and Ic, and the peculiar Type II that makes a transition to Ib, are collected and analyzed. Their main characteristics are (1) a group of fast and heterogeneous light curves corresponding to spectroscopic Type Ic and (2) a group of intermediate and homogeneous light curves among which are examples of spectroscopic Types Ib, Ic, and II transition. The latter have a well-defined slope of ~0.019 mag day -1 after ~150 days. A simple model based on the deposition of the energy provided by the radioactive decay of 56 Ni and 56 Co in expanding spherical shells is presented and used to qualitatively explain these families of light curves. The γ-ray deposition function has two different regimes. At early times, it is strongly dependent on the physical parameters of the shells, which explains the heterogeneity of group 1 above. At late times, however, it reaches an asymptotic regime in which the slope in excess of the 56 Co decay rate is given by 5 t -1 log e mag day -1 , where t is the time since explosion in days, independently of any parameter of the ejecta. The photometric group 2 above may be, at least partially, a result of this asymptotic behavior.