The Nickel Mass Distribution of Stripped-envelope Supernovae: Implications for Additional Power Sources

• Published in: The Astrophysical journal 2021-09, Vol.918 (2), p.89
• Main Authors: Afsariardchi, Niloufar, Drout, Maria R., Khatami, David K., Matzner, Christopher D., Moon, Dae-Sik, Ni, Yuan Qi
• Format: Article
• Language: English
• Subjects: Astrophysics; Composition effects; Core-collapse supernovae; Hydrogen; Luminosity; Magnetars; Mass distribution; Mathematical models; Modelling; Nickel; Numerical simulations; Photosphere; Power sources; Progenitors (astrophysics); Radioactive decay; Shock cooling; Supernova; Supernovae
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ac0aeb

We perform a systematic study of the 56 Ni mass ( M Ni ) of 27 stripped-envelope supernovae (SESNe) by modeling their light-curve tails, highlighting that use of “Arnett’s rule” overestimates M Ni for SESNe by a factor of ∼2. Recently, Khatami & Kasen presented a new model relating the peak time ( t p ) and luminosity ( L p ) of a radioactively powered supernova to its M Ni that addresses several limitations of Arnett-like models, but depends on a dimensionless parameter, β . Using observed t p , L p , and tail-measured M Ni values for 27 SESNe, we observationally calibrate β for the first time. Despite scatter, we demonstrate that the model of Khatami & Kasen with empirically calibrated β values provides significantly improved measurements of M Ni when only photospheric data are available. However, these observationally constrained β values are systematically lower than those inferred from numerical simulations, primarily because the observed sample has significantly higher (0.2–0.4 dex) L p for a given M Ni . While effects due to composition, mixing, and asymmetry can increase L p none can explain the systematically low β values. However, the discrepancy can be alleviated if ∼7%–50% of L p for the observed sample comes from sources other than radioactive decay. Either shock cooling or magnetar spin-down could provide the requisite luminosity. Finally, we find that even with our improved measurements, the M Ni values of SESNe are still a factor of ∼3 larger than those of hydrogen-rich Type II SNe, indicating that these supernovae are inherently different in terms of the initial mass distributions of their progenitors or their explosion mechanisms.