Multimessenger Gamma-Ray and Neutrino Coincidence Alerts using HAWC and IceCube sub-threshold Data

TL;DR

This paper presents a real-time multimessenger search for extragalactic sources emitting both gamma rays and neutrinos using HAWC and IceCube data, identifying coincident events with low false alarm rates.

Contribution

It introduces a novel real-time analysis algorithm within the AMON framework that combines sub-threshold gamma-ray and neutrino data for multimessenger astrophysics.

Findings

Two coincident events detected with FAR <1/year during archival data analysis.

Real-time alerts issued since November 2019 with FAR <4/year.

Method demonstrates effective multimessenger coincidence detection.

Abstract

The High Altitude Water Cherenkov (HAWC) and IceCube observatories, through the Astrophysical Multimessenger Observatory Network (AMON) framework, have developed a multimessenger joint search for extragalactic astrophysical sources. This analysis looks for sources that emit both cosmic neutrinos and gamma rays that are produced in photo-hadronic or hadronic interactions. The AMON system is running continuously, receiving sub-threshold data (i.e. data that is not suited on its own to do astrophysical searches) from HAWC and IceCube, and combining them in real-time. We present here the analysis algorithm, as well as results from archival data collected between June 2015 and August 2018, with a total live-time of 3.0 years. During this period we found two coincident events that have a false alarm rate (FAR) of $<1$ coincidence per year, consistent with the background expectations. The real-time implementation of the analysis in the AMON system began on November 20th, 2019, and issues alerts to the community through the Gamma-ray Coordinates Network with a FAR threshold of $<4$ coincidences per year.