Studying the nature of the astrophysical transient AT2025zjx

Abstract

Intermediate-Luminosity Red Transients (ILRTs) are a class of gap transients situated between the two extremes of classical novae and core-collapse supernovae in terms of their peak luminosity. In this work, a photometric and spectroscopic study of the transient event AT2025zjx is presented, making use of observations carried out at a dozen observatories around the world. The transient took place in the interacting galactic system NGC 520 and presents a light curve with a single maximum with an absolute magnitude of Mr = −14.27 ± 0.15. The event exhibits a slow cooling with a mild reddening of the continuum, accompanied by narrow Balmer, Ca II, and [Ca II] lines in its spectra, as well as a decrease of the Na I D absorption line due to the interaction with the dense surrounding material. The evolution of the Balmer decrement (Hα/Hβ) suggests possible dust formation in late phases. The event AT2025zjx is classified as a fast-decaying ILRT, whose properties likely represent the final explosion of a dust-enshrouded super-AGB star.