Giant outbursts of clumpy material preceding Type II supernova 2024qiw

¹ Department of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland
² Aalto University Metsähovi Radio Observatory, Metsähovintie 114, 02540 Kylmälä, Finland
³ Aalto University Department of Electronics and Nanoengineering, P.O. BOX 15500, FI-00076 Aalto, Finland
⁴ National Astronomical Observatory of Japan, National Institutes of Natural Sciences, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
⁵ Finnish Centre for Astronomy with ESO (FINCA), FI-20014 University of Turku, Finland
⁶ Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan
⁷ School of Sciences, European University Cyprus, Diogenes Street, Engomi, 1516 Nicosia, Cyprus
⁸ Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
⁹ Astrophysics Research Cluster, School of Mathematical and Physical Sciences, University of Sheffield, Sheffield S3 7RH, UK

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Received: 4 December 2025
Accepted: 8 March 2026

Abstract

Observations of core-collapse supernovae (CCSNe) suggest that some massive stars undergo intense mass loss shortly before explosion, but the underlying mechanisms remain unknown. Here, we report evidence of giant outbursts of clumpy material from a massive star in the final decades before explosion. Photometric, spectroscopic, and polarimetric data of SN 2024qiw reveal a bumpy light curve, a broad Hα profile, and variable polarization, all consistent with interactions taking place between SN ejecta and clumpy circumstellar material, implying a mass-loss rate of ≳10⁻² M_⊙ yr⁻¹. Taken together, the most likely explanation is multiple major eruptions, similar to those of luminous blue variables (LBVs), but occurring shortly before explosion. This challenges standard stellar evolution theory by requiring either that LBVs explode terminally or that other evolutionary phases produce eruptive episodes. In spite of very high pre-SN mass loss, the resulting SN is classed as Type II, rather than Type IIn, highlighting diverse and previously unrecognized late-stage mass-loss processes.