Brennan, SJ, Schulze, S, Lunnan, R, Sollerman, J, Yan, L, Fransson, C, Irani, I, Melinder, J, Chen, TW, De, K, Fremling, C, Kim, YL, Perley, D, Pessi, PJ, Drake, AJ, Graham, MJ, Laher, RR, Masci, FJ, Purdum, J and Rodriguez, H (2024) SN 2021adxl: A luminous nearby interacting supernova in an extremely low-metallicity environment. Astronomy & Astrophysics, 690. ISSN 0004-6361

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Abstract

SN 2021adxl is a slowly evolving, luminous, Type IIn supernova with asymmetric emission line profiles, similar to the well-studied SN 2010jl. We present extensive optical, near-ultraviolet, and near-infrared photometry and spectroscopy covering ~1.5 years post discovery. SN 2021adxl occurred in an unusual environment, atop a vigorously star-forming region that is offset from its host galaxy core. The appearance of Lyα and O ii, as well as the compact core, would classify the host of SN 2021adxl as a “Blueberry” galaxy, analogous to higher redshift, low-metallicity, star-forming dwarf “Green Pea” galaxies. Using several abundance indicators, we find a metallicity of the explosion environment of only [Formula Presented], the lowest reported metallicity for a Type IIn SN environment. SN 2021adxl reaches a peak magnitude of Mr ≈ −20.2 mag and since discovery, SN 2021adxl has faded by only ~4 magnitudes in the r band with a cumulative radiated energy of ~1.5 × 1050 erg over 18 months. SN 2021adxl shows strong signs of interaction with a complex circumstellar medium, seen by the detection of X-rays, revealed by the detection of coronal emission lines, and through multicomponent hydrogen and helium profiles. In order to further understand this interaction, we model the Hα profile using a Monte Carlo electron scattering code. The blueshifted high-velocity component is consistent with emission from a radially thin spherical shell resulting in the broad emission components due to electron scattering. Using the velocity evolution of this emitting shell, we find that the SN ejecta collide with circumstellar material of at least [Formula Presented] assuming a steady-state mass-loss rate of ~4−6 × 10−3 M yr−1 for the first ~200 days of evolution. SN 2021adxl was last observed to be slowly declining at ~0.01 mag d−1, and if this trend continues, SN 2021adxl will remain observable after its current solar conjunction. Continuing the observations of SN 2021adxl may reveal signatures of dust formation or an infrared excess, similar to that seen for SN 2010jl.

Item Type:	Article
Uncontrolled Keywords:	0201 Astronomical and Space Sciences; Astronomy & Astrophysics
Subjects:	Q Science > QB Astronomy Q Science > QC Physics
Divisions:	Astrophysics Research Institute
Publisher:	EDP Sciences
SWORD Depositor:	A Symplectic
Date Deposited:	15 Nov 2024 16:58
Last Modified:	15 Nov 2024 17:00
DOI or ID number:	10.1051/0004-6361/202349036
URI:	https://researchonline.ljmu.ac.uk/id/eprint/24794

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