First constraints on point-like astrophysical sources using Baikal-GVD muon neutrino events

TL;DR

This paper reports on the search for astrophysical point-like neutrino sources using the Baikal-GVD detector, setting competitive upper limits and demonstrating the detector's potential for neutrino astronomy.

Contribution

First constraints on point-like astrophysical sources using Baikal-GVD muon neutrino events, employing a novel track reconstruction and analysis method with partial detector data.

Findings

No significant neutrino excess detected from 92 sources.

Upper limits on neutrino fluxes are competitive with ANTARES and KM3NeT.

Indication of a possible low-significance excess from Westerlund 1.

Abstract

Baikal-GVD is a new-generation neutrino telescope currently under construction in Lake Baikal, Russia. With an instrumented volume already at 0.7 km$^3$, Baikal-GVD is currently the largest neutrino telescope in the Northern hemisphere. A sub-degree angular resolution, made possible thanks to high purity of Baikal water, further enhances Baikal-GVD sensitivity to cosmic neutrino sources. In this work, we employ track-like events collected from the partially completed detector between April 2019 and March 2024 to search for muon neutrino fluxes from 92 astrophysical objects of interest. For this, a $\chi^2$-based track reconstruction method is used along with a cut-based analysis. The analysis uses upward-going muons only, providing coverage for declinations between -90$^\circ$ and +38$^\circ$. No significant excess has been found, so upper limits are reported. The obtained limits are competitive with those set by ANTARES and KM3NeT. We briefly comment on a possible low-significance indication of an excess from the direction of Westerlund 1. This work sets a major milestone on the way to full-scale scientific exploitation of Baikal-GVD data.