Very Long Baseline Interferometry Observations of the Proposed Radio Counterpart of an EGRET Source

TL;DR

This study uses high-resolution VLBI imaging over multiple epochs to analyze the radio source J1826+3431, revealing superluminal motion, Doppler boosting, and flux variability, supporting its association with a gamma-ray source.

Contribution

It provides detailed VLBI observations and analysis of J1826+3431, demonstrating its blazar characteristics and strengthening its link to the gamma-ray source 3EG J1824+3441.

Findings

Detection of superluminal motion in the jet

High brightness temperature indicating Doppler boosting

Substantial flux density variability observed

Abstract

We present high-resolution radio interferometric imaging observations of the radio source NVSS J182659+343113 (hereafter J1826+3431), the proposed radio counterpart of the ${\gamma}$-ray source, 3EG J1824+3441 detected by the Energetic Gamma Ray Experiment Telescope (EGRET) on board the Compton Gamma Ray Observatory satellite. We analyzed eight epochs of archival multi-frequency very long baseline interferometry data. We imaged the asymmetric core-jet structure of the source, and detected apparent superluminal motion in the jet. At the highest observing frequency, 15.3 GHz, the core shows high brightness temperature indicating Doppler boosting. Additionally, the radio features undergo substantial flux density variability. These findings strengthen the previous claim of the association of the blazar J1826+3431 with the possible ${\gamma}$-ray source, 3EG J1824+3441.