Speaker
Description
We present results from our comprehensive multiwavelength studies of the FSRQ 3C 279 (Krishna Mohana A et al. 2024, MNRAS, 527, 6970; 2025, ApJ, 989, 125) — one of the brightest and most variable blazars in the gamma-ray sky — alongside the first data release of the quasi-Simultaneous Multiwavelength Monitoring of gamma-ray-loud AGNs with the Nanshan 26 m radio telescope (SMMAN; Cui, Krishna Mohana A et al. 2026, ApJS, 283, 69). We carried out a multiband radio cross-correlation analysis of 3C 279 spanning over a decade (2008–2022) across seven frequency bands ranging from 2 to 230 GHz. Prominent flares appear first at higher frequencies and propagate to lower frequencies, with lag–frequency relations well described by linear fits of slope $\sim -30$ day GHz$^{-1}$. By comparing these variations with the evolution of bright moving knots in multi-epoch VLBA maps, we infer physical changes in the jet, with some variations consistent with shock propagation and others better explained by a change in the Doppler beaming factor as the knot trajectory bends slightly, given a small viewing angle to the jet. Extending this to a full broadband perspective, we model 168 quasi-simultaneous SEDs constructed from Fermi-LAT, Swift-XRT/UVOT, WEBT, and radio data over the $\sim14$-year Fermi era. A one-zone leptonic scenario, with the emission region outside the broad-line region, successfully reproduces the observed emission, revealing that flares are driven by increases in the Doppler beaming factor coupled with variations in the emitting electron population. The SMMAN program has monitored 131 northern gamma-ray-loud AGN at 4.8 and 23.6 GHz over eight years (2016-2024) with the Nanshan 26 m Telescope. Sources show stronger variability at 23.6 GHz, with BL Lacs more variable than FSRQs. FSRQs are more radio-luminous, and both classes exhibit higher gamma-ray loudness than radio galaxies. The SMMAN dataset, incorporated with other historical and ongoing monitoring programs, will provide a unique opportunity to investigate the evolution of SEDs, search for QPOs, and analyse supermassive black hole binary systems.