Modelling type IIP/IIL supernovae interacting with recent episodic mass ejections from their presupernova stars with MESA & SNEC

Abstract

We show how dense compact discrete shells of circumstellar gas immediately outside the red supergiants affect the optical light curves of type II-P/II-L SNe taking the example of SN 2013ej. The earlier efforts in the literature had used an artificial circumstellar medium (CSM) stitched to the surface of an evolved star which had not gone through a phase of late-stage heavy mass loss, which in essence, is the source of the CSM to begin with. In contrast we allow enhanced mass loss rate from the modeled star during the $^{16}$O and $^{28}$Si burning stages and construct the CSM from the resulting mass-loss history in a self-consistent way. Once such evolved pre-SN stars are exploded, we find that the models with early interaction between the shock and the dense CSM reproduce the light curves far better than those without that mass loss and hence having no dense, nearby CSM. The required explosion energy for the progenitors with a dense CSM is reduced by almost a factor of two compared to those without the CSM. Our model, with a more realistic CSM profile and presupernova and explosion parameters, fits observed data much better throughout the rise, plateau and radioactive tail phases compared to previous studies. This points to an intermediate class of supernovae between type II-P/II-L and type II-n SNe with the characteristics of simultaneous UV and optical peak, slow decline after peak and a longer plateau.