“Core-collapse supernovae (CCSNe) mark the explosive deaths of massive (>8-10Msun) stars. Among these, Type II supernovae (SNeII) are the most common, originating from red supergiant (RSG) progenitors that retain their hydrogen-rich envelopes. A subclass of SNeII are type IIn, which exhibit narrow emission lines in their spectra, caused by the interaction between the SN ejecta and dense, slow-moving circumstellar material (CSM) near the progenitor star. Recent early-time observations of SNe II, obtained within hours to days after explosion, have revealed spectra dominated by narrow, highly ionized emission lines,  indicating strong interaction with CSM. These features gradually disappear after a few days, giving way to spectra typical of normal SNe II. However, how a RSG progenitor produces the required dense CSM is still unclear.
In this talk, I will discuss how early-time observations of two of the closest SNe II in the past decade, SN 2023ixf and SN 2024ggi, contribute to our understanding of progenitor properties and CSM interaction. Additionally, I will present results from a study of 70 SNe II with photometric and spectroscopic data, which aims to bridge the gap between single SN studies showing early-time interaction in their spectra, and  statistical studies of early-time SN light curves.”