Search for multi-flare neutrino emissions in 10 years of IceCube data from a catalog of sources

TL;DR

This study conducts time-dependent searches for neutrino emissions from a catalog of sources using 10 years of IceCube data, identifying potential flares and cumulative excesses, and advancing methods to detect multiple flares from individual sources.

Contribution

Introduces novel time-dependent analysis methods to identify multiple neutrino flares from sources, improving sensitivity over previous approaches.

Findings

M87 is the most significant time-dependent source at 1.7σ post-trial.

Two flares are reconstructed from TXS 0506+056.

A cumulative excess at 3.0σ is associated with four sources.

Abstract

A recent time-integrated analysis of a catalog of 110 candidate neutrino sources revealed a cumulative neutrino excess in the data collected by IceCube between April 6, 2008 and July 10, 2018. This excess, inconsistent with the background hypothesis in the Northern hemisphere at the $3.3~\sigma$ level, is associated with four sources: NGC 1068, TXS 0506+056, PKS 1424+240 and GB6 J1542+6129. This letter presents two time-dependent neutrino emission searches on the same data sample and catalog: a point-source search that looks for the most significant time-dependent source of the catalog by combining space, energy and time information of the events, and a population test based on binomial statistics that looks for a cumulative time-dependent neutrino excess from a subset of sources. Compared to previous time-dependent searches, these analyses enable a feature to possibly find multiple flares from a single direction with an unbinned maximum-likelihood method. M87 is found to be the most significant time-dependent source of this catalog at the level of $1.7~\sigma$ post-trial, and TXS 0506+056 is the only source for which two flares are reconstructed. The binomial test reports a cumulative time-dependent neutrino excess in the Northern hemisphere at the level of $3.0~\sigma$ associated with four sources: M87, TXS 0506+056, GB6 J1542+6129 and NGC 1068.