Very blue-shifted broad Hα in a low-redshift type-1.9 active galactic nucleus: a disc-emitter or a recoiling black hole scenario?

In this work, we provide a detailed analysis of the broadband temporal and spectral properties of the blazar Ton\, 599 by using the observations from Fermi-LAT and Swift-XRT/UVOT telescopes, during its brightest -ray flaring. The one-day bin -ray light curve exhibits multiple substructures with asymmetric and symmetric profiles. Notably, the -ray light curve shows a maximum flux of 3. 63 10^-6\, ph \, cm^-2\, s^-1 on MJD\, 59954. 50, which is the highest flux ever observed from this source. The correlation between the -ray flux and -ray spectral indices suggests a moderate harder when the brighter trend. Taking -ray light curve as the reference, a strong correlation is observed with X-ray, optical, and UV energies. Additionally, the -rays and optical/UV emissions exhibit higher variability compared to X-rays. To understand the parameter variation during the active state of the source, we conducted a statistical broadband spectral modelling of the source in 10 flux intervals of equal duration. A one-zone leptonic model involving synchrotron, synchrotron-self-Compton, and external-Compton processes successfully reproduces the broadband SED in each of these flux intervals. We observed that the flux variation during the active state is mainly associated with the variation in the magnetic field and the particle spectral indices.