Fermi blazars as candidate neutrino emitters: a study of temporal coincidence with IceCube events

Multimessenger astronomy provides a unique tool for exploring the universe at the highest energies: the association between neutrinos and their astrophysical sources would constitute a powerful probe of the high-energy sky. In 2017, the neutrino event IceCube-170922A was found to be coincident in arrival time and direction with an enhanced γ-ray activity from the blazar TXS 0506+056 at redshift z ∼ 0.34, and it was associated to this source at the 3σ confidence level. This discovery motivates further research in the field of the blazar-neutrino connection. In this work, the temporal coincidence between the arrival times of IceCube neutrinos and the γ-ray (0.1 − 300 GeV) emission from a sample of Fermi-detected blazars is investigated. The spatial coincidence for the same sample had been investigated in a previous reference work. Different criteria for the definition of the flaring state of a source were adopted depending on the blazar class (HBL/IBL or LBL) and a subsample of 4 flare-neutrino coincident blazars was selected. A statistical test was performed on each class separately in order to assess the nature of the observed coincidences. An interesting excess was found for the class of HBLs/IBLs while no excess was observed for the LBLs. I discussed the implications of these results for the blazar neutrino connection and the future perspectives for this work.