Unmasking the Active Galactic Nucleus in PKS J2310-437

TL;DR

This study provides detailed multi-wavelength observations of PKS J2310-437, revealing its core properties, variability, and emission mechanisms, and challenges existing AGN models by showing significant optical and X-ray variability.

Contribution

It offers new optical, radio, and X-ray measurements of PKS J2310-437, clarifying its emission processes and variability, and refines understanding of AGN with weak jets and bright X-ray cores.

Findings

Optical excess associated with the AGN detected

Radio core varies by about 20% over 38 months

X-ray emission consistent with synchrotron radiation

Abstract

PKS J2310-437 is an AGN with bright X-ray emission relative to its weak radio emission and optical continuum. It is believed that its jet lies far enough from the line of sight that it is not highly relativistically beamed. It thus provides an extreme test of AGN models. We present new observations aimed at refining the measurement of the source's properties. In optical photometry with the NTT we measure a central excess with relatively steep spectrum lying above the bright elliptical galaxy emission, and we associate the excess wholly or in part with the AGN. A new full-track radio observation with the ATCA finds that the core 8.64GHz emission has varied by about 20 per cent over 38 months, and improves the mapping of the weak jet. With Chandra we measure a well-constrained power-law spectral index for the X-ray core, uncontaminated by extended emission from the cluster environment, with a negligible level of intrinsic absorption. Weak X-ray emission from the resolved radio jet is also measured. Our analysis suggests that the optical continuum in this radio galaxy has varied by at least a factor of four over a timescale of about two years, something that should be testable with further observations. We conclude that the most likely explanation for the bright central X-ray emission is synchrotron radiation from high-energy electrons.