PKS~2332$-$017 and PMN J1916$-$1519: Candidate Blazar Counterparts to Two High-energy Neutrino Events

TL;DR

This study identifies two blazars as potential sources of high-energy neutrinos, linking gamma-ray flares and multi-wavelength variability to neutrino emission, advancing understanding of astrophysical neutrino origins.

Contribution

The paper presents the first association of specific blazars with high-energy neutrino events through multi-wavelength analysis and gamma-ray flare correlation.

Findings

PKS 2332-017 and PMN J1916-1519 are likely neutrino sources.

Gamma-ray flares coincided with neutrino detection times.

Optical and MIR brightening observed during flares.

Abstract

We report our counterpart identification study for two high-energy neutrino events IC-130127A and IC-131204A listed in the IceCube Event Catalog of Alert Tracks. These two events belong to Gold alerts, which have a significant probability of being of astrophysical origin.Within the events' 90\% positional uncertainty regions, we respectively find PKS~2332$-$017 and PMN J1916$-$1519. The first source is a flat-spectrum radio quasar at redshift $z= 1.18$ and the second a blazar of an uncertain type with photometric $z= 0.968$. As they correspondingly had a $\gamma$-ray flare temporally coincident with the arrival times of IC-130127A and IC-131204A, we identify them as the respective neutrino emitters. Detailed analysis of the $\gamma$-ray data for the two blazars, obtained with the Large Area Telescope (LAT) onboard {\it the Fermi Gamma-ray Space Telescope (Fermi)}, is conducted. The two flares respectively from PKS~2332$-$017 and PMN~J1916$-$1519 lasted $\sim$4\,yr and $\sim$4\,month, and showed possible emission hardening by containing high-energy $\sim$2--10\,GeV photons in the emissions. Accompanying the flare of PKS~2332$-$017, optical and MIR brightening variations were also observed. We discuss the properties of the two sources and compare the properties with those of the previously reported (candidate) neutrino-emitting blazars.