2025/12/05 by Kumar, Harsh, Blanchard, Peter K., Berger, Edo +8
Engineering · Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Astrophysics of Galaxies (astro-ph.GA) #CCD and CMOS Imaging Sensors #FOS: Physical sciences #Gamma-ray bursts and supernovae #High Energy Astrophysical Phenomena (astro-ph.HE) #Solar and Stellar Astrophysics (astro-ph.SR)
paper · doi:10.48550/arxiv.2512.06067
openalex publication_date 2025/12/05 · openalex created_date 2025/12/10 · openalex updated_date 2026/07/28
We present a comprehensive optical and near-infrared spectroscopic study of SN 2024afav - a hydrogen-poor superluminous supernova (SLSN-I) that peaks at ≈ -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 Hα 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 Hα; (iii) early appearance of nebular [O III] emission starting at ≈ +50 d; and (iv) strong [O II] + [Ca II] 7300 Å emission complex starting at ≈ +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.