SN 2022xus: bridging the gap between Type IIP and IIL supernovae

Le résumé fourni par la source

ABSTRACT We present optical photometric and spectroscopic observations of the Type II supernova SN 2022xus. The supernova (SN) reached its peak V-band magnitude of ${-}16.32$ mag within $\sim$7 d of explosion, followed by a plateau phase lasting $\sim$94 d with a declination rate of $\sim$1.2 mag (100 d)$^{-1}$. Early-time spectra exhibit broad features that could be caused by the blending of several high-ionization lines, likely arising from a relatively weak interaction between the SN ejecta and the surrounding circumstellar medium (CSM). Compared to typical Type IIP SNe, SN 2022xus exhibits a smaller H $\alpha$ absorption-to-emission ratio ($a/e$), indicating a relatively small hydrogen envelope mass at the time of explosion. From nebular-phase spectroscopy and bolometric light-curve modelling, the progenitor mass is estimated to be in the range of 12–15 M$_\odot$. The multiband light-curve modelling using redback infers a similar progenitor mass, a low mass-loss rate, and a confined CSM. Although several photometric and spectroscopic characteristics place the SN within the Type IIL population, it displays mixed properties of both Type IIP and Type IIL SNe and cannot be cleanly classified into either subclass. We therefore identify SN 2022xus as a transitional event between Type IIP and Type IIL SNe, providing further evidence for a continuum between these two classes.

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