On the origin of multifrequency temporal and spectral variability in Ton 599

TL;DR

This study analyzes the broadband variability of the quasar Ton 599 during a long flaring episode, revealing correlated emissions across multiple wavelengths, stochastic variability, and insights into the physical processes driving its activity.

Contribution

It provides a comprehensive multi-wavelength analysis of Ton 599, including flux state identification, variability characterization, and modeling of emission mechanisms during a prolonged flaring event.

Findings

Detection of three distinct flares and flux states.

Identification of pink-noise stochastic variability without a spectral break.

Evidence of disk-jet coupling from thermal black body emission.

Abstract

In this work, we studied the broadband temporal and spectral properties of the flat-spectrum radio quasar (FSRQ) Ton 599. We collected the long-term data from Jan 2019 to August 2024 when the source was in a long flaring episode. We used the Bayesian block methodology to identify the various flux states, including three flares. The broadband fractional variability is estimated during two flaring states. The Fvar variation with respect to frequency shows a nearly double hump structure similar to broadband SED. The Power spectral density (PSD) shows a pink-noise kind of stochastic variability in the light curve and we do not see any break in the power spectrum, suggesting a much longer characteristic time scale is involved in gamma-ray variability. The flux distribution is well-fitted with a double log-normal flux distribution, suggesting the variability of non-linear in nature. The gamma-ray, optical, and X-ray emissions were found to be highly correlated with a zero time lag, suggesting a co-spatial origin of their emissions. We used the one-zone leptonic model to reproduce the broad-band spectrum in the energy range from IR to very high-energy gamma-ray. The increase in the magnetic field and the Doppler factor were found to be the main cause for high flux states. The XMM-Newton spectra taken during one of the flaring durations exhibit a signature of thermal black body emission from the accretion disk, suggesting a possible disk-jet coupling. This has also been indicated by the gamma-ray flux distribution, which shows the distribution as non-linear in nature, which is mostly seen in galactic X-ray binaries or AGN where the accretion disk dominates the emission.