FRAMEx II: Simultaneous X-ray and Radio Variability in Active Galactic Nuclei $-$ The Case of NGC 2992

TL;DR

This study presents the first simultaneous X-ray and radio variability observations of NGC 2992, revealing correlated changes likely driven by magnetic reconnection events affecting the accretion disk and broad line region.

Contribution

It provides new insights into the physical connection between X-ray and radio emissions in AGNs through simultaneous multi-wavelength observations.

Findings

Large radio luminosity drop (>3x) coincided with >5x increase in X-ray luminosity.

X-ray spectral index remained unchanged during the flare.

Radio luminosity change explained by free-free absorption in the broad line region.

Abstract

Using simultaneous Very Long Baseline Array and Neil Gehrels Swift Observatory X-ray Telescope observations of the active galactic nucleus (AGN) in NGC 2992 over a six-month observing campaign, we observed a large drop in core 5 cm radio luminosity, by a factor of $>3$, in tandem with factor of $>5$ increase in $2-10$ keV X-ray luminosity. While NGC 2992 has long been an important object for studies of X-ray variability, our study is the first simultaneous X-ray and radio variability campaign on this object. We observe that the X-ray spectral index does not change over the course of the flare, consistent with a change in the bulk amount of Comptonizing plasma, potentially due to a magnetic reconnection event in the accretion disk. The drop in apparent radio luminosity can be explained by a change in free-free absorption, which we calculate to correspond to an ionized region with physical extent and electron density consistent with the broad line region (BLR). Our results are consistent with magnetic reconnection events in the dynamic accretion disk creating outbursts of ionizing material, increasing Compton up-scattering of UV accretion disk photons and feeding material into the BLR. These findings present an important physical picture for the dynamical relationship between X-ray and radio emission in AGNs.