56Ni masses in supernovae

These SE-SN distributions were then compared to those compiled in this article. Results. Arnett's rule, as previously shown, gives ^56^Ni masses for SE-SNe that are considerably higher than SNe II.

While for the distributions calculated using both the Khatami & Kasen (2019ApJ...878...56K) prescription and Tail ^56^Ni masses are offset to lower values than "Arnett values", their ^56^Ni distributions are still statistically higher than that of SNe II. Our results are strongly driven by a lack of SE-SN with low ^56^Ni masses, that are, in addition, strictly lower limits. The lowest SE-SN ^56^Ni mass in our sample is of 0.015M_{sun}_, below which are more than 25% of SNe II.

We conclude that there exist real, intrinsic differences in the mass of synthesised radioactive material between SNe II and SE-SNe (types IIb, Ib, and Ic). Any proposed current or future CC SN progenitor scenario and explosion mechanism must be able to explain why and how such differences arise or outline a bias in current SN samples yet to be fully explored.