2016MNRAS.458.2094D

Using radiation hydrodynamics and radiative transfer simulations, we explore the origin of the spectral diversity of interacting supernovae (SNe) of Type IIn. We revisit SN 1994W and investigate the dynamical configurations that can give rise to spectra with narrow lines at all times. We find that a standard ∼10 M_☉ 10⁵¹ ergSN ejecta ramming into a 0.4 M_☉ dense circumstellar material is inadequate for SN 1994W, as it leads to the appearance of broad lines at late times. This structure, however, generates spectra that exhibit the key morphological changes seen in SN 1998S. For SN 1994W, we consider a completely different configuration, which involves the interaction at a large radius of a low-mass inner shell with a high-mass outer shell. Such a structure may arise in an 8-12 M_☉ star from a nuclear flash (e.g. of Ne) followed within a few years by core collapse. Our simulations show that the large mass of the outer shell leads to the complete braking of the inner shell material, the formation of a slow dense shell, and the powering of a luminous SN IIn, even for a low inner shell energy. Early on, our model line profiles are typical of SNe IIn, exhibiting narrow cores and broad electron-scattering wings. As observed in SN 1994W, they also remain narrow at late times. Our SN 1994W model invokes two low-energy ejections, both atypical of observed massive stars, and illustrates the diversity of configurations leading to SNe IIn. These results also highlight the importance of spectra to constrain the dynamical properties and understand the origin of SNe IIn.