An X-Ray View of the Jet-Cycle in the Radio Loud AGN 3C120

TL;DR

This study investigates the central engine of radio galaxy 3C120 through multi-epoch X-ray and radio observations, supporting the jet-cycle paradigm with evidence of disk truncation, refilling, and jet ejection events.

Contribution

It provides a composite jet+disk model that explains spectral data and supports the jet-cycle paradigm with observational evidence of disk state changes and jet ejections.

Findings

Disk refilling and truncation observed during different epochs.

Detection of a new jet knot after disk refilling.

Observation of a step-like event with band lag indicating disturbance propagation.

Abstract

We present a study of the central engine in the broad-line radio galaxy 3C120 using a multi-epoch analysis of a deep XMM-Newton observation and two deep Suzaku pointings (in 2012). In order to place our spectral data into the context of the disk-disruption/jet-ejection cycles displayed by this object, we monitor the source in the UV/X-ray bands, and in the radio band. We find three statistically acceptable spectral models, a disk-reflection model, a jet-model and a jet+disk model. Despite being good descriptions of the data, the disk-reflection model violates the radio constraints on the inclination, and the jet-model has a fine-tuning problem, requiring a jet contribution exceeding that expected. Thus, we argue for a composite jet+disk model. Within the context of this model, we verify the basic predictions of the jet-cycle paradigm, finding a truncated/refilling disk during the Suzaku observations and a complete disk extending down to the innermost stable circular orbit (ISCO) during the XMM-Newton observation. The idea of a refilling disk is further supported by the detection of the ejection of a new jet knot approximately one month after the Suzaku pointings. We also discover a step-like event in one of the Suzaku pointings in which the soft band lags the hard band. We suggest that we are witnessing the propagation of a disturbance from the disk into the jet on a timescale set by the magnetic field.