SN 2025wiu: A Type Ib Supernova with Post-Peak Optical Rebrightening
Abstract
We present optical photometric and optical/near-infrared spectroscopic observations of SN 2025wiu, a Type Ib supernova (SN) at z = 0.046927. The r-band light curve exhibits an initial maximum of approximately -18.2 mag, followed by a weaker optical rebrightening reaching approximately -17.8 mag at +38 days in the rest frame relative to the first maximum. However, the reconstructed bolometric light curve does not show a distinct second peak, but instead exhibits a reduced decline rate during the corresponding phase. The spectra consistently show Type Ib features without narrow emission components associated with circumstellar material. The late-time bolometric decline rate of 0.054 +/- 0.008 mag/day is faster than expected for complete trapping of 56Co decay. A radioactive-decay model for the first peak requires nickel mass = 0.47 solar masses, above the range typical of SNe Ib. A combined radioactive-decay and circumstellar-interaction model reproduces the full bolometric light curve with nickel mass ~ 0.38 solar masses, ejecta mass ~ 4.7 solar masses, and an effective circumstellar mass of ~ 0.10 solar masses, with the interaction contributing from the first peak onward. The lack of interaction signatures in the spectra favours an aspherical, disk-like circumstellar structure engulfed by the ejecta, in which the interaction energy is thermalized below the ejecta photosphere; the fitted circumstellar parameters are therefore effective values rather than direct measurements of the circumstellar geometry. SN 2025wiu demonstrates that optical rebrightening does not necessarily imply a genuine bolometric secondary maximum and highlights the importance of multi-band observations for identifying the powering mechanisms of double-peaked stripped-envelope supernovae.
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BibTeX
@misc{lai20262025wiu,
title = {{SN 2025wiu: A Type Ib Supernova with Post-Peak Optical Rebrightening}},
author = {Cheng-Han Lai and Ting-Wan Chen and Yu-Hao Zhang and Liang-Duan Liu and Jesper Sollerman and Amar Aryan and Anirban Dutta and Sheng Yang and Christoffer Fremling and Matthew J. Graham and David Hale and K. -Ryan Hinds and Mansi M. Kasliwal and Frank J. Masci and Reed L. Riddle and Sam Rose and Ben Rusholme and Niharika Sravan},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.23414},
eprint = {2610.23414},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.23414},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - SN 2025wiu: A Type Ib Supernova with Post-Peak Optical Rebrightening
AU - Cheng-Han Lai
AU - Ting-Wan Chen
AU - Yu-Hao Zhang
AU - Liang-Duan Liu
AU - Jesper Sollerman
AU - Amar Aryan
AU - Anirban Dutta
AU - Sheng Yang
AU - Christoffer Fremling
AU - Matthew J. Graham
AU - David Hale
AU - K. -Ryan Hinds
AU - Mansi M. Kasliwal
AU - Frank J. Masci
AU - Reed L. Riddle
AU - Sam Rose
AU - Ben Rusholme
AU - Niharika Sravan
PY - 2026
DA - 2026/10/16
PB - arXiv
DO - 10.48550/arxiv.2610.23414
UR - https://arxiv.org/abs/2610.23414
AB - We present optical photometric and optical/near-infrared spectroscopic observations of SN 2025wiu, a Type Ib supernova (SN) at z = 0.046927. The r-band light curve exhibits an initial maximum of approximately -18.2 mag, followed by a weaker optical rebrightening reaching approximately -17.8 mag at +38 days in the rest frame relative to the first maximum. However, the reconstructed bolometric light curve does not show a distinct second peak, but instead exhibits a reduced decline rate during the corresponding phase. The spectra consistently show Type Ib features without narrow emission components associated with circumstellar material. The late-time bolometric decline rate of 0.054 +/- 0.008 mag/day is faster than expected for complete trapping of 56Co decay. A radioactive-decay model for the first peak requires nickel mass = 0.47 solar masses, above the range typical of SNe Ib. A combined radioactive-decay and circumstellar-interaction model reproduces the full bolometric light curve with nickel mass ~ 0.38 solar masses, ejecta mass ~ 4.7 solar masses, and an effective circumstellar mass of ~ 0.10 solar masses, with the interaction contributing from the first peak onward. The lack of interaction signatures in the spectra favours an aspherical, disk-like circumstellar structure engulfed by the ejecta, in which the interaction energy is thermalized below the ejecta photosphere; the fitted circumstellar parameters are therefore effective values rather than direct measurements of the circumstellar geometry. SN 2025wiu demonstrates that optical rebrightening does not necessarily imply a genuine bolometric secondary maximum and highlights the importance of multi-band observations for identifying the powering mechanisms of double-peaked stripped-envelope supernovae.
ER -