STELLA lightcurves of energetic pair instability supernovae in the context of SN2018ibb

Abstract

SN2018ibb is a recently observed hydrogen poor super-luminous supernova which appears to be powered by the decay of $30\;\rm{M_\odot}$ of radioactive nickel. This supernova has been suggested to show hybrid signatures of a pair instability supernova and an interacting supernova. In a previous paper, we found that rotating, metal enriched pair instability supernova progenitors appeared to check both of these boxes. In this paper, we model the lightcurves of the pair instability supernovae using STELLA. We find that the STELLA models can explain the overall shape of the bolometric lightcurve of SN2018ibb, though not specific morphological features such as the luminosity peak or the bump at roughly three hundred days after the peak. We also estimate the contribution from interaction, and find that with relatively low wind velocities, the circum-stellar medium originating from the stellar winds is consistent with the evidence for interaction in the spectra. The observed values of the photosphere velocity in the hundred days after peak luminosity are similar to the STELLA models, but the deceleration is lower. This leads to the biggest inconsistency which is the black body temperature of SN2018ibb being much hotter than any of the STELLA models. We note that this high temperature (and the flat velocity) may be difficult to reconcile with the long rise time of SN2018ibb, but nevertheless conclude that if it is accurate, this discrepancy represents a challenge for SN2018ibb being a robust PISN candidate. This result is noteworthy given the lack of other scenarios for this supernova.