Unlocking the secrets of supernovae through their light curves, spectra & polarization

Utilizing the radiative transfer code cmfgen, we have undertaken time-dependent radiative transfer calculations that compute the light curve and spectra for Type Ia, Ib, Ic, and II supernovae (SNe) through the photospheric and nebular phases. The non-LTE calculations allow for a multitude of atomic processes (bound–bound, bound–free, free–free, collisional, charge exchange, and Penning ionization) and for non-thermal excitation and ionization from non-thermal electrons created by the degradation in energy of high-energy (∼1 MeV) gamma-rays. The proper inclusion of all these processes requires a vast amount of atomic data. Not all the atomic data is available, and the quality of the available atomic data varies considerably. We have confirmed the results of Utrobin and Chugai (2005) that time dependent terms must be included in the statistical equilibrium equations in order to model the Hα evolution of SN 1987A, shown that time dependent terms influence other spectral features, and shown that these conclusions also apply to the modeling of Type II SNe in general. The inclusion of non-thermal processes has allowed us to model Hα and He i emission in Type II SNe into the nebular phase, and to model the He i emission in Type Ib and Ic SNe. Our calculations show that the He deficiency in Ic SNe is unlikely to be real – instead, the absence of He i on SNe Ic spectra is more likely related to inefficient excitation of He iions. Simply by varying the amount of mixing we are able to create spectra of Type Ib and Ic SNe using the SAME progenitor model. Based on a new grid of SNe Ib/c models, we confirm previous findings that the typically fast-rising narrow-peak fast-declining SNe Ib/c light curves imply ejecta masses ≲5M⊙, favoring intermediate-mass massive stars in interacting binaries. We are successfully applying cmfgen to model Type Ia SNe, and are currently exploring the role of mixing and non-thermal processes in these SNe. We highlight the differences between the various classes of SNe.