Probing Jet Conditions with Multi-frequency, Centimeter-band Linear Polarization: PKS 0420-01

TL;DR

This study uses multi-frequency polarization observations to analyze jet conditions in blazar PKS 0420-01 during a gamma-ray flare, identifying shocks and constraining jet parameters near the gamma-ray emission site.

Contribution

It introduces a method to probe jet conditions at parsec scales using polarization data during gamma-ray flares, revealing shock dynamics and jet parameters.

Findings

Identified three forward-moving shocks during the flare.

Determined shock Lorentz factor of 12.

Estimated observer's viewing angle of 2 degrees.

Abstract

We have used single-dish centimeter-band, multi-frequency linear polarization and total flux density monitoring observations obtained by UMRAO at 14.5, 8, and 4.8 GHz during gamma-ray flaring to constrain propagating shock-in-jet models; this procedure allows us to probe jet conditions at or near the presumed parsec-scale gamma-ray emission site within the relativistic jet. Results are presented for the blazar 0420-014 during the gamma-ray flare detected by the LAT which peaked in late January 2010. Our work identifies the passage of three forward-moving transverse shocks during the radio-band flaring, a shock Lorentz factor of 12, and an observer's viewing angle of 2 degrees and sets limits on the energy distribution of the radiating particles.