The Nickel Mass Distribution of Normal Type II Supernovae

Core-collapse supernova (SN) explosions expose the structure and environment of massive stars at the moment of their death. We use the global fitting technique of Pejcha & Prieto to estimate a set of physical parameters of 19 normal SNe II, such as their distance moduli, reddenings, ⁵⁶Ni masses {M}_{Ni}, and explosion energies {E}_\exp from multicolor light curves and photospheric velocity curves. We confirm and characterize known correlations between {M}_{Ni} and bolometric luminosity at 50 days after the explosion, and between {M}_{Ni} and {E}_\exp . We pay special attention to the observed distribution of {M}_{Ni} coming from a joint sample of 38 SNe II, which can be described as a skewed-Gaussian-like distribution between 0.005 {M}_⊙ and 0.280 {M}_⊙ , with a median of 0.031 {M}_⊙ , mean of 0.046 {M}_⊙ , standard deviation of 0.048 {M}_⊙ , and skewness of 3.050. We use a two-sample Kolmogorov-Smirnov test and two-sample Anderson-Darling test to compare the observed distribution of {M}_{Ni} to results from theoretical hydrodynamical codes of core-collapse explosions with the neutrino mechanism presented in the literature. Our results show that the theoretical distributions obtained from the codes tested in this work, KEPLER and Prometheus Hot Bubble, are compatible with the observations irrespective of different pre-SN calibrations and different maximum mass of the progenitors.