SN 2021aaev: a Hydrogen-Rich Superluminous Supernova with Early Flash and Long-Lived Circumstellar Interaction in an Unusual Host Environment

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Main Authors: Hu, Yang, Lunnan, Ragnhild, Pessi, Priscila J., Saldana-Lopez, Alberto, Jerkstrand, Anders, Sollerman, Jesper, Schulze, Steve, Anderson, Joseph P., Brennan, Seán J., Cosentino, Stefano P., Gangopadhyay, Anjasha, Gkini, Anamaria, Gromadzki, Mariusz, Hayes, Matthew J., Inserra, Cosimo, Müller-Bravo, Tomás E., Nicholl, Matt, Pignata, Giuliano, Singh, Avinash, Wise, Jacob L., Yan, Lin, Adler, Judy, Chen, Ting-Wan, Chen, Tracy X., Kasliwal, Mansi M., Pessi, Thallis, Salmaso, Irene, Young, David R.
Format: Preprint
Published: 2025
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author Hu, Yang
Lunnan, Ragnhild
Pessi, Priscila J.
Saldana-Lopez, Alberto
Jerkstrand, Anders
Sollerman, Jesper
Schulze, Steve
Anderson, Joseph P.
Brennan, Seán J.
Cosentino, Stefano P.
Gangopadhyay, Anjasha
Gkini, Anamaria
Gromadzki, Mariusz
Hayes, Matthew J.
Inserra, Cosimo
Müller-Bravo, Tomás E.
Nicholl, Matt
Pignata, Giuliano
Singh, Avinash
Wise, Jacob L.
Yan, Lin
Adler, Judy
Chen, Ting-Wan
Chen, Tracy X.
Kasliwal, Mansi M.
Pessi, Thallis
Salmaso, Irene
Young, David R.
author_facet Hu, Yang
Lunnan, Ragnhild
Pessi, Priscila J.
Saldana-Lopez, Alberto
Jerkstrand, Anders
Sollerman, Jesper
Schulze, Steve
Anderson, Joseph P.
Brennan, Seán J.
Cosentino, Stefano P.
Gangopadhyay, Anjasha
Gkini, Anamaria
Gromadzki, Mariusz
Hayes, Matthew J.
Inserra, Cosimo
Müller-Bravo, Tomás E.
Nicholl, Matt
Pignata, Giuliano
Singh, Avinash
Wise, Jacob L.
Yan, Lin
Adler, Judy
Chen, Ting-Wan
Chen, Tracy X.
Kasliwal, Mansi M.
Pessi, Thallis
Salmaso, Irene
Young, David R.
contents We present photometric and spectroscopic observations of SN\,2021aaev, a hydrogen-rich, superluminous supernova with persistent (at least $\sim100$ days) narrow Balmer lines (SLSN-IIn) at redshift $z=0.1557$. We observed SN\,2021aaev to rise in $32.5 \pm 1.0$ days since first light and reach a peak absolute magnitude of $-21.46 \pm 0.01$ in the ATLAS $o$ band. The pre-peak spectra resemble those of typical SNe IIn with flash-ionization features arising from the interaction with a dense, confined circumstellar medium (CSM), albeit the flash timescale is longer than usual ($>20$ days). Post peak, the narrow emission lines evolve slowly, and the absence of ejecta features indicates strong deceleration by the CSM. The total radiated energy (about $1.41\times10^{51}$~ergs) is possible with a low-mass (1--$2\,M_{\odot}$) ejecta ploughing into a massive (9--$19\,M_{\odot}$), extended (outer radius $>1\times10^{16}$~cm) H-rich CSM, or alternatively, with magnetar-powered models. Interestingly, the host environment consists of a spiral galaxy with a red substructure in the south-eastern part, and the SN's exact location coincided with the quiescent red substructure (star-formation rate$=0.02^{+0.13}_{-0.02}\,M_{\odot}$~yr$^{-1}$). Given the atypical environment and the obscuring effect of the massive CSM, a thermonuclear (Type Ia-CSM) origin cannot be ruled out. Altogether, SN\,2021aaev is a compelling case to study the diversity of SLSN-IIn features and their host environment.
format Preprint
id arxiv_https___arxiv_org_abs_2508_11559
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle SN 2021aaev: a Hydrogen-Rich Superluminous Supernova with Early Flash and Long-Lived Circumstellar Interaction in an Unusual Host Environment
Hu, Yang
Lunnan, Ragnhild
Pessi, Priscila J.
Saldana-Lopez, Alberto
Jerkstrand, Anders
Sollerman, Jesper
Schulze, Steve
Anderson, Joseph P.
Brennan, Seán J.
Cosentino, Stefano P.
Gangopadhyay, Anjasha
Gkini, Anamaria
Gromadzki, Mariusz
Hayes, Matthew J.
Inserra, Cosimo
Müller-Bravo, Tomás E.
Nicholl, Matt
Pignata, Giuliano
Singh, Avinash
Wise, Jacob L.
Yan, Lin
Adler, Judy
Chen, Ting-Wan
Chen, Tracy X.
Kasliwal, Mansi M.
Pessi, Thallis
Salmaso, Irene
Young, David R.
High Energy Astrophysical Phenomena
Astrophysics of Galaxies
We present photometric and spectroscopic observations of SN\,2021aaev, a hydrogen-rich, superluminous supernova with persistent (at least $\sim100$ days) narrow Balmer lines (SLSN-IIn) at redshift $z=0.1557$. We observed SN\,2021aaev to rise in $32.5 \pm 1.0$ days since first light and reach a peak absolute magnitude of $-21.46 \pm 0.01$ in the ATLAS $o$ band. The pre-peak spectra resemble those of typical SNe IIn with flash-ionization features arising from the interaction with a dense, confined circumstellar medium (CSM), albeit the flash timescale is longer than usual ($>20$ days). Post peak, the narrow emission lines evolve slowly, and the absence of ejecta features indicates strong deceleration by the CSM. The total radiated energy (about $1.41\times10^{51}$~ergs) is possible with a low-mass (1--$2\,M_{\odot}$) ejecta ploughing into a massive (9--$19\,M_{\odot}$), extended (outer radius $>1\times10^{16}$~cm) H-rich CSM, or alternatively, with magnetar-powered models. Interestingly, the host environment consists of a spiral galaxy with a red substructure in the south-eastern part, and the SN's exact location coincided with the quiescent red substructure (star-formation rate$=0.02^{+0.13}_{-0.02}\,M_{\odot}$~yr$^{-1}$). Given the atypical environment and the obscuring effect of the massive CSM, a thermonuclear (Type Ia-CSM) origin cannot be ruled out. Altogether, SN\,2021aaev is a compelling case to study the diversity of SLSN-IIn features and their host environment.
title SN 2021aaev: a Hydrogen-Rich Superluminous Supernova with Early Flash and Long-Lived Circumstellar Interaction in an Unusual Host Environment
topic High Energy Astrophysical Phenomena
Astrophysics of Galaxies
url https://arxiv.org/abs/2508.11559