Multiple Flares in the Changing-Look AGN NGC 5273

TL;DR

This study tracks the long-term multi-wavelength variability of NGC 5273, revealing multiple changing-look events and their connection to accretion processes, including the rare observation of NIR broad lines appearing during these transitions.

Contribution

It provides a detailed multi-epoch analysis of NGC 5273's changing-look behavior, including the first NIR broad line detection during such events, highlighting complex accretion dynamics.

Findings

Multiple changing-look events identified from 2000 to 2022.

First NIR broad Paschen lines observed in a changing-look AGN.

Variable luminosity influences the broad line region reprocessing.

Abstract

NGC 5273 is a known optical and X-ray variable AGN. We analyze new and archival IR, optical, UV, and X-ray data in order to characterize its long-term variability from 2000 to 2022. At least one optical changing-look event occurred between 2011 and 2014, when the AGN changed from a Type 1.8/1.9 Seyfert to a Type 1. It then faded considerably at all wavelengths, followed by a dramatic but slow increase in UV/optical brightness between 2021 and 2022. Near-IR (NIR) spectra in 2022 show prominent broad Paschen lines that are absent in an archival spectrum from 2010, making NGC 5273 one of the few AGNs to be observed changing-look in the NIR. We propose that NGC 5273 underwent multiple changing-look events between 2000 and 2022 -- starting as a Type 1.8/1.9, NGC 5273 changes-look to a Type 1 temporarily in 2002 and again in 2014, reverting back to a Type 1.8/1.9 by 2005 and 2017, respectively. In 2022, it is again a Type 1 Seyfert. We characterize the changing-look events and their connection to the dynamic accretion and radiative processes in NGC 5273, and propose that the variable luminosity (and thus, Eddington ratio) of the source is changing how the broad line region (BLR) reprocesses the continuum emission.