The Extreme Gamma-Ray Blazar S5 0716+714: Jet Conditions from Radio-Band Variability and Radiative Transfer Modeling

TL;DR

This study combines radio-band variability observations and radiative transfer modeling to investigate the physical conditions in the jet of the gamma-ray blazar S5 0716+714, revealing multiple strong shocks and jet parameters.

Contribution

It introduces a detailed analysis of radio variability and shock modeling to constrain jet conditions in a gamma-ray blazar, advancing understanding of jet physics during flaring events.

Findings

Identification of eight forward-moving shocks with high compression factors

Determination of shock Lorentz factor of 77 and flow Lorentz factor of 20

Constraints on jet viewing angle and opening angle

Abstract

As part of a program to identify the physical conditions in the jets of gamma-ray-flaring blazars detected by Fermi, including the role of shocks in the production of high-energy flaring, we obtained 4 years of 3-frequency, centimeter-band total flux density and linear polarization monitoring observations of the radio-bright blazar S5 0716+714 with the University of Michigan 26-m paraboloid. Light curves constructed from these data exhibit a series of rapid, high-amplitude, centimeter-band total flux density outbursts, and changes in the linear polarization consistent with the passage of shocks during the gamma-ray flaring. The observed spectral evolution of the radio-band flares, in combination with radiative transfer simulations incorporating propagating shocks, was used to constrain the shock and jet flow conditions in the parsec-scale regions of the jet. Eight forward-moving, transverse shocks with unusually-strong shock compression factors, a very fast Lorentz factor of the shocks of 77, a bulk Lorentz factor of the flow of 20, a viewing angle of 12 degrees, and an intrinsic opening angle of the radio jet of 5.2 degrees were identified.