Zooming into the neutrino-associated blazar candidate J1718+4239

TL;DR

This study used VLBI observations to confirm that the radio source J1718+4239 is a blazar, showing variable, Doppler-boosted emission with a compact structure, supporting its candidacy as a neutrino source.

Contribution

First VLBI observations of J1718+4239 that reveal its blazar nature through detailed radio analysis, confirming its potential as a neutrino-associated source.

Findings

Detected highly variable, Doppler-boosted radio emission.

Confirmed compact structure at multiple scales.

Identified a jet inclination angle of ≤5 degrees.

Abstract

The radio quasar NVSS~J171822+423948 (J1718+4239) was proposed as the counterpart of the IceCube neutrino event IC-201221A. To reveal the nature of the source, we conducted new very long baseline interferometry (VLBI) observations of this blazar candidate with the Very Long Baseline Array (VLBA). The observations were carried out in dual-band mode between $4$ and $7$~GHz. Archival radio data from the literature were also collected for comparison. Our analysis revealed highly variable, Doppler-boosted radio emission of the source, with compact structure at both kpc and pc scales, a slightly inverted spectrum, and a maximum jet inclination angle of $\theta\le5\degr$. These results confirm J1718+4239 as a blazar-type object.