Explosion Imminent: the appearance of Red Supergiants at the point of core-collapse

Abstract

From the early radiation of type II-P supernovae (SNe), it has been claimed that the majority of their red supergiant (RSG) progenitors are enshrouded by large amounts of circumstellar material (CSM) at the point of explosion. The inferred density of this CSM is orders of magnitude above that seen around RSGs in the field, and is therefore indicative of a short phase of elevated mass-loss prior to explosion. It is not known over what timescale this material gets there: is it formed over several decades by a `superwind' with mass-loss rate $\dot{M}\sim 10^{-3}{\mathrm{M}}_{\odot }\mathrm{y}{\mathrm{r}}^{-1}$; or is it formed in less than a year by a brief `outburst' with $\dot{M}\sim 10^{-1}{\mathrm{M}}_{\odot }\mathrm{y}{\mathrm{r}}^{-1}$? In this paper, we simulate spectra for RSGs undergoing such mass-loss events, and demonstrate that in either scenario the CSM suppresses the optical flux by over a factor of 100, and that of the near-IR by a factor of 10. We argue that the `superwind' model can be excluded as it causes the progenitor to be heavily obscured for decades before explosion, and is strongly at odds with observations of II-P progenitors taken within 10 years of core-collapse. Instead, our results favour abrupt outbursts $<$1 year before explosion as the explanation for the early optical radiation of II-P SNe. We therefore predict that RSGs will undergo dramatic photometric variability in the optical and infrared in the weeks-to-months before core-collapse.

8 pages, 7 figures. Accepted for publication in MNRAS

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• A Luminous Red Supergiant and Dusty Long-period Variable Progenitor for SN 2023ixf
• Synthetic red supergiant explosion model grid for systematic characterization of Type II supernovae
• Using spectral modeling to break light-curve degeneracies of type II supernovae interacting with circumstellar material
• Identifying the SN 2022acko progenitor with JWST
• The effect of mass loss in models of red supergiants in the Small Magellanic Cloud
• Precursors of Supernovae from Mass Eruption: Prospects for Early Warning of Nearby Core-collapse Supernovae
• Investigating episodic mass loss in evolved massive stars: I. Spectroscopy of dusty massive stars in ten southern galaxies
• Sample of hydrogen-rich superluminous supernovae from the Zwicky Transient Facility
• Inferring CSM Properties of Type II SNe Using a Magnitude-Limited ZTF Sample
• One Year of SN 2023ixf: Breaking Through the Degenerate Parameter Space in Light-Curve Models with Pulsating Progenitors
• Stellar evolution through the Red Supergiant phase