Unveiling the nature of SN 2022jli: The first double-peaked stripped-envelope supernova showing periodic undulations and dust emission at late times

¹ Gemini Observatory, NSF’s National Optical-Infrared Astronomy Research Laboratory Casilla 603 La Serena, Chile
² Instituto de Estudios Astrofísicos, Facultad de Ingeniería y Ciencias, Universidad Diego Portales Av. Ejército Libertador 441 Santiago, Chile
³ Centro de Astronomía (CITEVA), Universidad de Antofagasta Avenida Angamos 601 Antofagasta, Chile
⁴ Las Campanas Observatory, Carnegie Observatories Casilla 601 La Serena, Chile
⁵ Department of Physics and Astronomy, Aarhus University Ny Munkegade 120 DK-8000 Aarhus C, Denmark
⁶ Fundación Chilena de Astronomía Santiago, Chile
⁷ Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas c/. Serrano 121 E-28006 Madrid, Spain
⁸ Institut de Ciències del Cosmos (UB-IEEC) c/. Martí i Franqués 1 E-080228 Barcelona, Spain
⁹ Millennium Institute of Astrophysics MAS, Nuncio Monseñor Sotero Sanz 100 Off. 104 Providencia Santiago, Chile
¹⁰ European Southern Observatory Alonso de Córdova 3107 Casilla 19 Santiago, Chile
¹¹ Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile Av. Vicuña Mackenna 4860 Santiago, Chile

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Received: 24 October 2024
Accepted: 7 September 2025

Abstract

We present optical and infrared observations from maximum light until around +800 days of supernova (SN) 2022jli, a peculiar stripped-envelope (SE) SN showing two maxima, each one with a peak luminosity of about 3 × 10⁴² erg s⁻¹, separated by 50 days. The second maximum is followed by unprecedented periodic undulations with a period of P ∼ 12.5 days. The spectra and the photometric evolution of the first maximum are consistent with the behaviour of a standard SE SN with an ejecta mass of ∼1.5 M_⊙ and a radioactive ⁵⁶Ni mass of ∼0.12 M_⊙. The optical spectra after +400 days relative to the first maximum correspond to a standard SN Ic event, and at late times SN 2022jli exhibits a significant drop in the optical luminosity, implying that the physical phenomena that produced the secondary maximum have ceased to power the SN light curve. Among other potential scenarios, we discuss how the second maximum could be powered by a magnetar, while the light curve periodic undulations could be produced by accretion of material from a companion star onto the neutron star in a binary system. The near-infrared spectra shows clear first CO overtone emission from about +190 days after the first maximum, and it becomes undetected at +400 days. A significant near-infrared excess from hot dust emission is detected at +238 days, having been produced by either newly formed dust in the SN ejecta or a strong near-infrared dust echo. Depending on the assumptions of the dust composition, the estimated dust mass is 2 − 16 × 10⁻⁴ M_⊙. The potential magnetar power of the second maximum can fit into a more general picture in which magnetars are the power source of SE super-luminous SNe, and could explain bumps, undulations, and late-time excess emission in SE SNe. The CO detection and the dust emission of SN 2022jli are key to understanding the molecule and dust formation in the ejecta of SE SNe and in their environment.