$\textit{Fermi}$-LAT realtime follow-ups of high-energy neutrino alerts

TL;DR

This paper discusses how the Fermi-LAT telescope conducts real-time follow-ups of high-energy neutrino alerts to identify gamma-ray counterparts, enhancing multi-messenger astronomy efforts.

Contribution

It presents the strategies and activities for real-time gamma-ray follow-up of neutrino alerts using Fermi-LAT, including recent observations and future improvements.

Findings

Identification of gamma-ray sources coincident with neutrino alerts

Successful real-time follow-up strategies implemented

Future plans for improved neutrino-gamma-ray counterpart detection

Abstract

The detection of the flaring gamma-ray blazar TXS 0506+056 in spatial and temporal coincidence with the high-energy neutrino IC-170922A represents a milestone for multi-messenger astronomy. The prompt multi-wavelength coverage from several ground- and space-based facilities of this special event was enabled thanks to the key role of the $\textit{Fermi}$-Large Area Telescope (LAT), continuously monitoring the gamma-ray sky. Exceptional variable and transient events, such as bright gamma-ray flares of blazars, are regularly reported to the whole astronomical community to enable prompt multi-wavelength observations of the astrophysical sources. As soon as realtime IceCube high-energy neutrino event alerts are received, the relevant positions are searched, at multiple timescales, for gamma-ray activity from known sources and newly detected emitters positionally consistent with the neutrino localization. In this contribution, we present an overview of follow-up activities and strategies for the realtime neutrino alerts with the $\textit{Fermi}$-LAT, focusing on some interesting coincidences observed with gamma-ray sources. We will also discuss future plans and improvements in the strategies for the identification of gamma-ray counterparts of single high-energy neutrinos.