Type II-Plateau supernova radiation: dependencies on progenitor and explosion properties

TL;DR

This study models Type II-Plateau supernovae and their red-supergiant progenitors, revealing how progenitor properties influence supernova radiation, colors, and spectral features, with implications for understanding progenitor characteristics and metallicity effects.

Contribution

The paper extends supernova radiation modeling to include detailed phases and spectra without LTE assumptions, highlighting the impact of progenitor size, rotation, and metallicity on supernova observables.

Findings

Large FeI and FeII model atoms are necessary for accurate color modeling.

Progenitor stars larger than ~500Rsun produce too blue supernova colors.

Supernova color evolution is insensitive to explosion energy variations.

Abstract

We explore the properties of Type II-Plateau (II-P) supernovae (SNe) together with their red-supergiant (RSG) star progenitors. Using MESA STAR, we modulate the parameters (e.g., mixing length, overshoot, rotation, metallicity) that control the evolution of a 15Msun main-sequence star to produce a variety of physical pre-SN models and SN II-P ejecta. We extend previous modeling of SN II-P radiation to include photospheric and nebular phases, as well as multi-band light curves and spectra. Our treatment does not assume local thermodynamic equilibrium, is time dependent, treats explicitly the effects of line blanketing, and incorporates non-thermal processes. We find that the color properties of SNe II-P require large model atoms for FeI and FeII, much larger than adopted in Dessart & Hillier (2011). The color properties also imply RSG progenitors of limited extent (~500Rsun) --- larger progenitor stars produce a SN II-P radiation that remains too blue for too long. This finding calls for a reduction of RSG radii, perhaps through a strengthening of convective energy transport in RSG envelopes. Increased overshoot and rotation reduce the ratio of ejecta to helium-core mass, similarly to an increase in main-sequence mass, and thus complicate the inference ofprogenitor masses. In contrast to the great sensitivity on progenitor radius, SN II-P color evolution appears insensitive to variations in explosion energy. Finally, we document the numerous SN II-P signatures that vary with progenitor metallicity, revealing their potential for metallicity determinations in the nearby and distant Universe.