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arXiv · 2512.06067

SN 2024afav: A Superluminous Supernova with Multiple Light Curve Bumps and Spectroscopic Signatures of Circumstellar Interaction

Harsh Kumar·Peter K. Blanchard·Edo Berger·Wasundara Athukoralalage·Daichi Hiramatsu·Sebastian Gomez·Moira Andrews·K. Azalee Bostroem·Joseph R. Farah·D. Andrew Howell·Curtis McCully
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Abstract

We present a comprehensive optical and near-infrared spectroscopic study of SN 2024afav - a hydrogen-poor superluminous supernova (SLSN-I) that peaks at $\approx$ -20.7 mag and exhibits an unusual multi-bumped light curve. Our spectroscopic observations, spanning phases of -14 to +160 d, reveal several unusual features: (i) a narrow (1,800 km s$^{-1}$) and blueshifted (11,000 km s$^{-1}$) absorption from H$\alpha$ starting at +20 d; (ii) persistent optical and NIR He I lines at all available phases, showing double absorption structure in NIR spectra at +23 d, with a high velocity component at a similar velocity to H$\alpha$; (iii) early appearance of nebular [O III] emission starting at $\approx$ +50 d; and (iv) strong [O II] + [Ca II] 7300 {\AA} emission complex starting at $\approx$ +110 d. These unusual features, and their onset at the time of the light curve bumps, provide compelling evidence of circumstellar interaction between the SN ejecta and a nearby hydrogen-rich shell, as well as the presence of helium in both the outer layers of the progenitor star and in the circumstellar medium. A comparison of SN 2024afav to other SLSNe-I showing bumpy light curves and similar spectral properties (PTF10hgi, SN 2017egm, SN 2019hge), points to a rare sub-group of SLSNe-I in which CSM interaction provides an important modulation to the energy input.

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Harsh Kumar, Peter K. Blanchard, Edo Berger, Wasundara Athukoralalage, Daichi Hiramatsu, Sebastian Gomez, Moira Andrews, K. Azalee Bostroem, Joseph R. Farah, D. Andrew Howell, Curtis McCully. 2025-12-05. SN 2024afav: A Superluminous Supernova with Multiple Light Curve Bumps and Spectroscopic Signatures of Circumstellar Interaction. https://arxiv.org/abs/2512.06067

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