Stripped-envelope core-collapse supernova ⁵⁶Ni masses

Abstract

Context. The mass of synthesised radioactive material is an important power source for all supernova (SN) types. In addition, the difference of 56Ni yields statistics are relevant to constrain progenitor paths and explosion mechanisms. Aims. Here, we re-estimate the nucleosynthetic yields of 56Ni for a well-observed and well-defined sample of stripped-envelope SNe (SE-SNe) in a uniform manner. This allows us to investigate whether the observed hydrogen-rich–stripped-envelope (SN II–SE SN) 56Ni separation is due to real differences between these SN types or because of systematic errors in the estimation methods. Methods. We compiled a sample of well-observed SE-SNe and measured 56Ni masses through three different methods proposed in the literature: first, the classic “Arnett rule”; second the more recent prescription of Khatami & Kasen (2019, ApJ, 878, 56) and third using the tail luminostiy to provide lower limit 56Ni masses. These SE-SN distributions were then compared to those compiled in this article. Results. Arnett’s rule, as previously shown, gives 56Ni masses for SE-SNe that are considerably higher than SNe II. While for the distributions calculated using both the Khatami & Kasen (2019, ApJ, 878, 56) prescription and Tail 56Ni masses are offset to lower values than “Arnett values”, their 56Ni distributions are still statistically higher than that of SNe II. Our results are strongly driven by a lack of SE-SN with low 56Ni masses, that are, in addition, strictly lower limits. The lowest SE-SN 56Ni mass in our sample is of 0.015 M⊙, below which are more than 25% of SNe II. Conclusions. 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.

Pre-supernova evolution, compact-object masses, and explosion properties of stripped binary stars

“…Observations of SN light curves suggest that, on average, stripped-envelope SNe produce more 56 Ni and are more energetic than SN IIP (e.g. Anderson 2019; Meza & Anderson 2020;Sharon & Kushnir 2020;Afsariardchi et al 2020), exactly as predicted by our models (Sect. 4.3).…”

Maximum luminosities of normal stripped-envelope supernovae are brighter than explosion models allow

“…A literature compilation by Anderson (2019) provides a calculated median of M56 Ni = 0.032 M for SNe II, and 0.163 and 0.155 M for SNe Ib and Ic, respectively. That study was repeated and augmented by Meza & Anderson (2020, see also Sharon & Kushnir 2020) concluding that there is a real, intrinsic difference in the amount of radioactive nickel between SNe II and SE SNe, even if the exact numbers are sensitive to the specific methodology.…”

Understanding the extreme luminosity of DES14X2fna

“…Again, this is not a Gaussian uncertainty, instead reflecting the maximum possible deviation due to uncertainty in explosion epoch. Meza & Anderson (2020) find SNe IIb and Ib 56 Ni masses that typically vary from ∼0.03-0.2 and ∼0.02-0.13 M using these methods, respectively. DES14X2fna would require a 56 Ni mass that is approximately four to five times larger than is typical for SNe IIb.…”

“…interaction with a surrounding circumstellar material (CSM) for SNe IIn; Moriya et al 2013), although a 56 Ni decay model can still be used to estimate some explosion properties (e.g. Prentice et al 2016;Meza & Anderson 2020). For SNe with light curves driven by 56 Ni decay such as SNe IIb, a more luminous SN indicates a higher synthesized mass of 56 Ni to power the peak of the light curve.…”