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

Abstract We present optical photometric and spectroscopic observations of the Type II supernova SN 2022xus. The SN reached its peak V band magnitude of −16.32 mag within ∼7 days of explosion, followed by a plateau phase lasting ∼94 days with a declination rate of ∼1.2 mag (100 day)−1. Early time spectra exhibit broad features that could be caused by the blending of several high-ionisation 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 Hα 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⊙. The multi-band 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.