Radiative Properties of Pair-instability Supernova Explosions

TL;DR

This paper models the radiative properties of pair-instability supernovae from various progenitors, revealing their light curves and spectra, and suggesting they are distinct from known super-luminous supernovae, with implications for high-redshift observations.

Contribution

It provides the first detailed non-LTE time-dependent radiative-transfer simulations of PISNe from physically-consistent progenitor models across different stellar types.

Findings

PISNe exhibit larger peak luminosities and longer durations than typical supernovae.

Spectra are dominated by FeII and FeI lines with red colors, especially post-peak.

PISNe are challenging to observe at high redshift due to their reddish appearance.

Abstract

We present non-LTE time-dependent radiative-transfer simulations of pair-instability supernovae (PISNe) stemming from red-supergiant (RSG), blue-supergiant (BSG) and Wolf-Rayet (WR) star rotation-free progenitors born in the mass range 160-230Msun, at 10^-4 Zsun. Although subject to uncertainties in convection and stellar mass-loss rates, our initial conditions come from physically-consistent models that treat evolution from the main-sequence, the onset of the pair-production instability, and the explosion phase. With our set of input models characterized by large 56Ni and ejecta masses, and large kinetic energies, we recover qualitatively the Type II-Plateau, II-peculiar, and Ib/c light-curve morphologies, although they have larger peak bolometric luminosities (~10^9 to 10^10 Lsun) and a longer duration (~200d). We discuss the spectral properties for each model during the photospheric and nebular phases, including Balmer lines in II-P and II-pec at early times, the dominance of lines from intermediate-mass-elements (IMEs) near the bolometric maximum, and the strengthening of metal line blanketing thereafter. Having similar He-core properties, all models exhibit similar post-peak spectra that are strongly blanketed by FeII and FeI lines, characterized by red colors, and that arise from photospheres/ejecta with a temperature of <4000K. Combined with the modest line widths after bolometric peak, these properties contrast with those of known super-luminous SNe suggesting that PISNe are yet to be discovered. Being reddish, PISNe will be difficult to observe at high redshift except when they stem from RSG explosions, in which case they could be used as metallicity probes and distance indicators.