Carpet-2 search for gamma rays above 100 TeV in coincidence with HAWC and IceCube alerts

TL;DR

This paper reports a search for ultra-high-energy gamma rays coinciding with HAWC and IceCube alerts using the Carpet-2 detector, setting upper limits and probing neutrino production in Galactic sources.

Contribution

First search combining HAWC and IceCube alerts with Carpet-2, providing new constraints on gamma-ray and neutrino emission from astrophysical sources.

Findings

No significant gamma-ray excess observed.

Upper limits set on gamma-ray fluences.

Constraints begin to probe neutrino production in Galactic flares.

Abstract

We report on the search of astrophysical gamma rays with energies in the 100 TeV to several PeV range arriving in directional and temporal coincidence with public alerts from HAWC (TeV gamma rays) and IceCube (neutrinos above ~100 TeV). The observations have been performed with the Carpet-2 air-shower detector at the Baksan Neutrino Observatory, working in the "photon-friendly" mode since 2018. Photon candidate showers are selected by their low muon content. No significant excess of the photon candidates have been observed, and upper limits on gamma-ray fluences associated with the alerts are obtained. For events with good viewing conditions, the Carpet-2 effective area for photons is of the order of the IceCube effective area for neutrinos of the same energy, so the constraints start to probe the production of neutrinos in fast flares of Galactic sources.