The role of radioactive nickel in shaping the plateau phase of Type II supernovae

Abstract

In the present study, we systematically explore the effect of the radioactive 56 Ni and its mixing properties in the ejecta on the plateau of Type IIP supernovae (SNe). We evaluate the importance of 56 Ni in shaping light curves of SNe IIP by simulating light curves for two red supergiant models using different amounts of 56 Ni and with different types of mixing: uniform distribution of 56 Ni out to different fractions of the envelope and "boxcar" distribution of 56 Ni. We find, similarly to previous studies, that 56 Ni extends duration of the plateau. We find a formula to estimate the extension based on the observed bolometric light curves and show that for most SNe IIP 56 Ni extends the plateau by about 20 %. Another effect of 56 Ni consists in reduction of the plateau decline rate, i.e. 56 Ni presented in the ejecta flattens the plateau. Our simulations suggest that for typical SNe IIP it can reduce the decline rate by about 1 mag/100 day. We find that for the contribution of 56 Ni seen in most SNe our simulated bolometric light curves resemble observed ones for various types of 56 Ni mixing. We thereby cannot determine the level of 56 Ni mixing in these SNe based on the light curve alone. However, for SN 2009ib we find that only a model where 56 Ni is mixed significantly throughout most of the hydrogen envelope is consistent with the observed light curve. Our light curves are available via link https://wwwmpa.mpa-garching.mpg.de/ ccsnarchive/data/Kozyreva2018/.

A Massive Star’s Dying Breaths: Pulsating Red Supergiants and Their Resulting Type IIP Supernovae

“…is the 56 Ni decay luminosity given in Nadyozhin (1994), which is taken to be equivalent to the instantaneous heating rate of the ejecta assuming complete trapping. ET also scales with the progenitor radius for constant M ej and E exp , given as ET ∝ R by the analytics and modeling of Nakar et al (2016); Shussman et al (2016); Kozyreva et al (2018), and as ET ∝ R 0.91 recovered from MESA+STELLA models by Goldberg et al (2019). The middle panel of Figure 7 shows the agreement between ET in our model lightcurves and the scalings.…”

Observational Signature of Circumstellar Interaction and 56Ni-mixing in the Type II Supernova 2016gfy

“…The plot description is same as Figure 10. The slightly higher 56 Ni mass estimate obtained using the steepness parameter in comparison with other techniques is an indication that the LC of SN 2016gfy exhibits a non-negligible degree of 56 Ni-mixing, which can decrease the steepness during the transition phase (Kozyreva et al 2019). 7.1.5.…”

“…Unlike the case of SN 2009ib, the slight bump noticed in SN 2016gfy could only be a result of centrally concentrated or partially mixed 56 Ni. As the bump is evident only past ∼ 50 d, the theoretical light curves in Kozyreva et al (2019) point towards a 56 Nimixing with one-third of the ejecta. Nakar et al (2016) defined two other dimensionless variables to quantify the effect of 56 Ni, given as:…”

Shock breakouts from red supergiants: analytical and numerical predictions

“…We examine the dependence of the colour temperature on explosion energy and radius based on a wider set of red supergiant models. In Figure 11, we show two models from Kozyreva et al (2019) for which explosion energy scatters in 1 foe, between roughly 0.5 foe and 1.5 foe. This range for explosion energy is valid for the normal SNe IIP according to Pejcha & Prieto (2015) and Müller et al (2017) on the one hand, and also from the core-collapse explosion simulations by Ertl et al (2016) and Sukhbold et al (2016), on the other hand.…”