Bright Type II SN 2023ixf in M101: A Quick Analysis of the Early-Stage Spectroscopic and Near-Infrared Light Curves

Abstract

We present the early-stage analysis of the low-resolution ($R=1000$) optical spectra and the near-infrared light curves of the bright Type II supernova (SN II) 2023ixf in the notable nearby face-on spiral galaxy M101, which are obtained since $t=1.7$ until $8.0$ d. Our first spectrum shows remarkable emission features of Balmer series, He~{\sc ii}, N~{\sc iv}, and C~{\sc iv} with a strong blue continuum. Compared with SNe II showing the flash-ionized features, we suggest that this SN could be categorized into high-luminosity SNe II with a nitrogen/helium-rich circumstellar material (CSM), e.g., SNe 2014G, 2017ahn, and 2020pni. The H~{$\alpha$} emission line is composed of broad (~2800 km~s$^{-1}$), intermediate (520 km~s$^{-1}$), and narrow ($<200$ km~s$^{-1}$) components. The near-infrared light curves are well consistent with those of another luminous SN II 2017ahn, and the absolute magnitudes locate on the bright end in the lumosity distribution of SNe II. These observational facts support that SN 2023ixf is well consistent with a high-luminosity SN II with the dense nitrogen/helium-rich CSM.Comment: 5 pages, 4 figures, submitted to PASJ Letter