SN 2021adxl: A luminous nearby interacting supernova in an extremely low-metallicity environment

Abstract

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 sim 1.5 years post discovery. occurred in an unusual environment, atop a vigorously star-forming region that is offset from its host galaxy core. The appearance of and O II as well as the compact core, would classify the host of 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 $ odot $, the lowest reported metallicity for a Type IIn SN environment. reaches a peak magnitude of _r mag and since discovery has faded by only sim 4 magnitudes in the $r$ band with a cumulative radiated energy of $ $ erg over 18 months. 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 multi-component hydrogen and helium profiles. In order to further understand this interaction, we model the 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 sim 5 assuming a steady-state mass-loss rate of $ for the first sim 200 days of evolution. was last observed to be slowly declining at $ mag $, and if this trend continues will remain observable after its current solar conjunction. Continuing the observations of may reveal signatures of dust formation or an infrared excess, similar to that seen for SN 2010jl.