A modeling perspective on the diversity of red-supergiant stars exploding within circumstellar material

TL;DR

This paper presents a comprehensive grid of radiation-hydrodynamics models to understand the diverse observational features of red-supergiant star explosions within circumstellar material, aiding future supernova observations.

Contribution

It introduces an extensive set of models covering various explosion energies and CSM properties, providing new insights into shock breakout signatures and spectral evolution in RSG supernovae.

Findings

CSM interaction enhances UV brightness and shortens optical rise time.

Higher ionization states are more prominent with compact CSM.

Spectral features are diversified by electron-scattering and Doppler broadening.

Abstract

With the ever faster cadence of untargeted surveys of the sky, the supernova (SN) community will capture in the coming years a growing number of shock breakouts in red-supergiant (RSG) stars. Expecting a high frequency of breakouts within circumstellar material (CSM), we have produced an extended, regular and cubic grid of models covering from low- to high-energy explosions, compact to extended CSM, moderate- to high-density CSM. Here, we document the main results from the radiation-hydrodynamics and nonlocal thermodynamic equilibrium radiative-transfer calculations over the first 15d of evolution, including the bolometric and multi-band light curves and the salient features from spectra. As before, CSM interaction is found to boost the UV brightness and shorten the optical rise time if compact. Higher ionization (e.g., as seen with OVI3820A) is obtained for more compact CSM, and is maximum for explosions in a vacuum. CSM interaction also diversifies the spectral evolution as seen in line profile morphology, with electron-scattering broadening dominating during the IIn phase. In the absence of CSM, Doppler broadening dominates immediately after shock breakout and leads to strongly blueshifted emission in lines such as HeII4686A or CIV5805A. This treasury of models will be used to analyze as well as predict future observations of RSG shock breakouts in CSM.