Bright Type II supernova 2023ixf in M 101: A quick analysis of the early-stage spectra and near-infrared light curves

Abstract

We present early-stage analyses of low-resolution (R = 1000) optical spectra and near-infrared light curves of the bright Type II supernova (SN II) 2023ixf in the notable nearby face-on spiral galaxy M 101, which were obtained from t = 1.7 to 8.0 d. Our first spectrum showed remarkable emission features of the Balmer series, He ii, N iii, C iv, and N iv with a strong blue continuum. Compared with the SNe II which show flash-ionized features, we suggest that this SN could be categorized as a high-luminosity SN II with a nitrogen/helium-rich circumstellar material (CSM), e.g., SNe 2014G, 2017ahn, and 2020pni. The Hα emission line can be tentatively explained by a narrower component with a velocity of <300 km s−1 and a broader one with ∼2200 km s−1. The near-infrared light curves were well consistent with those of the another luminous SN 2017ahn, and its absolute magnitudes are located at the bright end of the luminosity distribution of SNe II. These observational facts support that SN 2023ixf is well consistent with high-luminosity SNe II showing evidence of a dense nitrogen/helium-rich CSM.