A Multiwavelength study of the ongoing Changing-look AGN AT2021fxu

TL;DR

This study analyzes the multiwavelength behavior of the Changing-look AGN AT2021fxu, revealing spectral and brightness changes consistent with an accretion-rate-driven transition from Type-II to Type-1 AGN.

Contribution

It provides a detailed multiwavelength observational analysis of a Changing-look AGN, highlighting the spectral and brightness evolution during the transition.

Findings

Optical brightness increased by up to 0.6 magnitudes, UV by 1.1 magnitudes.

X-ray flux doubled post-outburst with stable spectral shape.

Spectral changes indicate a transition from Type-II to Type-1 AGN.

Abstract

We present multiwavelength analyses of an active optical transient AT2021fxu which shows the appearance of previously absent broad emission lines in a recent optical spectrum, suggesting a Changing-look (CL) Active Galactic Nucleus (AGN). During the spectral transition, the brightness in the individual photometric bands increased up to $\approx$0.6 in the optical bands and up to $\approx$1.1 magnitudes in the UV bands. The brightening was accompanied by a blueward shift of the optical spectrum. AT2021fxu shows high X-ray (0.3-10 keV) flux variability before and after the outburst, with the average X-ray flux increasing by a factor of $\approx$2 post-outburst. However, the X-ray spectral shape remains roughly the same, with no significant change in the line-of-sight column density. AT2021fxu's overall properties are consistent with an accretion-rate-driven transition from a Type-II to a Type-1 AGN.