Inferring the Progenitor Properties of ILRTs: A Combined Analysis of Observations and Theoretical Models

Among the most energetic phenomena in the universe, Supernovae are the most spectacular and exotic ones, reaching luminosities ranges $10^{41}-10^{43}$ erg$s^{-1} $ comparable with the luminosity of an entire galaxy. In the last few decades, large sky surveys have revealed new categories of astrophysical objects called "Gap transients", such as Luminous Blue Variables, Luminous Red Novae and Faint Supernovae. Despite the similarities in the energy range, Gap transients can originate from radically different physical processes and progenitor systems. In addition to these transient categories, recently discovered Intermediate-Luminosity Red Transients (ILRTs), represent a rare class of H-rich stellar explosions with typical peak bolometric luminosities around $10^{40}-10^{41}$erg$s^{-1}$, two order of magnitudes below the Supernovae type II, placing them between classical novae and core-collapse supernovae (CCSNe). A major challenge in interpreting ILRTs lies in the presence of a sufficiently dense, extended circumstellar medium (CSM), which strongly shapes the light curves through ejecta-CSM interaction. Despite growing observational efforts, the physical mechanism that produces this kind of transient sources is still debated, with electron capture SNe (ECSNe) from $8–10M_\odot$ progenitors being a leading scenario. In this work I present a novel semi-analytical model developed to describe the radiative output from the interaction between SN ejecta and a structured H-rich CSM, allowing me to place constraints on both the explosion properties and CSM configuration directly from the photometric data. Finally, I apply it to a well-monitored ILRT, SN 2019abn, offering insights into its progenitor and pre-explosion mass-loss history.