Explosions of pulsating red supergiants: A natural pathway for the diversity of Type II-P/L supernovae

¹ Heidelberger Institut für Theoretische Studien, Schloss-Wolfsbrunnenweg 35, 69118 Heidelberg, Germany
² Universität Heidelberg, Department of Physics and Astronomy, Im Neuenheimer Feld 226, 69120 Heidelberg, Germany
³ Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium
⁴ Leuven Gravity Institute, KU Leuven, Celestijnenlaan 200D, Box 2415 3001 Leuven, Belgium
⁵ Anton Pannekoek Institute of Astronomy, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands
⁶ Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut, Mönchhofstr. 12-14, 69120 Heidelberg, Germany
⁷ London Centre for Stellar Astrophysics, Vauxhall, London
⁸ University of Oxford, St Edmund Hall, Oxford OX1 4AR, UK

^⋆ Corresponding author: vincent.bronner@h-its.org

Received: 19 March 2025
Accepted: 1 September 2025

Abstract

Red supergiants (RSGs), which are progenitors of hydrogen-rich Type II supernovae (SNe), have been known to pulsate, both from observations and theory. The pulsations can be present at core collapse and affect the resulting SN. However, SN light curve models of such RSGs commonly use hydrostatic progenitor models and ignore pulsations. Here, we model the final stages of a 15 M_⊙ RSG and self-consistently follow the hydrodynamical evolution. We observe the growth of large-amplitude radial pulsations in the envelope. After a transient phase in which the envelope restructures, the pulsations settle to a steady and periodic oscillation with a period of 817 days. We show that they are driven by the κγ mechanism, which is an interplay between changing opacities and the release of recombination energy of hydrogen and helium. This leads to complex and incoherent expansion and contraction in different parts of the envelope, which greatly affects the SN progenitor properties, including its location in the Hertzsprung-Russell diagram. We simulate SN explosions of this model at different pulsation phases. Explosions in the compressed state result in a flat light curve (Type II-P). In contrast, the SN light curve in the expanded state declines rapidly, reminiscent of a Type II-L SN. For cases in between, we find light curves with various decline rates. Features in the SN light curves are directly connected to features in the density profiles. These are, in turn, linked to the envelope ionization structure, which is the driving mechanism of the pulsations. We predict that some of the observed diversity in Type II SN light curves can be explained by RSG pulsations. For more massive RSGs, we expect stronger pulsations that might even lead to dynamical mass ejections of the envelope and to an increased diversity in SN light curves.