Temporal Variability and Estimation of Jet Parameters for Ton 599

Abstract

The TeV blazar Ton 599 has exhibited a peculiar flare in 2017 November. The temporal variation of the source is studied using simultaneous γ -ray data from the Fermi Large Area Telescope and radio data from the Owens Valley Radio Observatory’s 40 m telescope, over the period of 9 yr. Four major flaring periods are observed in the γ -ray energy band of 0.1–300 GeV. These periods are studied on a shorter timescale and modeled with a time-dependent function containing exponential rising and decaying components. The physical parameters of the jet are estimated numerically and compared with those reported in the literature. During the fourth flare, a bunch of high-energy photons (>10 GeV) were detected. The two highest-energy photons, with energies of 76.9 and 61.9 GeV, are detected on MJD 58,059.0 and 58,073.3, respectively. This observation possibly constrains the γ -ray emission region to lie near the outer edge or outside the broad-line region of size ∼0.08 pc. The variation of equivalent width of an Mg ii line is studied using the spectroscopic data from Steward Observatory. It was observed that the equivalent width of the line varies inversely with the underlying power-law continuum.