Baikal-GVD Astrophysical Neutrino Candidate near the Blazar TXS~0506+056

TL;DR

This paper reports the detection of a high-energy neutrino event by Baikal-GVD, spatially and temporally associated with the blazar TXS~0506+056, suggesting a potential astrophysical neutrino source.

Contribution

First observation of a high-energy cascade neutrino event by Baikal-GVD linked to a known blazar, supporting neutrino source identification.

Findings

Detected a 224 TeV neutrino cascade with 97.1% signalness.

Event's arrival direction is consistent with blazar TXS~0506+056.

Radio flare observed after the neutrino event supports source association.

Abstract

We report on the observation of a rare neutrino event detected by Baikal-GVD in April 2021. The event GVD210418CA is the highest-energy cascade observed by Baikal-GVD so far from the direction below the horizon. The estimated cascade energy is $224\pm75$~TeV. The evaluated signalness parameter of GVD210418CA is 97.1\% using an assumption of the E$^{-2.46}$ spectrum of astrophysical neutrinos. The arrival direction of GVD210418CA is near the position of the well-known radio blazar TXS~0506+056, with the angular distance being within a 90\% directional uncertainty region of the Baikal-GVD measurement. The event was followed by a radio flare observed by the RATAN-600 radio telescope, further strengthening the case for the neutrino-blazar association.