Search for neutrino emission from blazar $γ$-ray flares accounting for possible neutrino time delays

Abstract

We report the results of the search for the high-energy neutrino emission associated with blazar flares, accounting for a possible lag of neutrinos with respect to the electromagnetic emission, either due to the slowness of the proton energy losses in $pγ$ collisions and/or proton acceleration. We perform two tests, cross-matching neutrinos with energies $E_ν \gtrsim 100$ TeV from the public catalogue of neutrino alerts IceCat-1 with active galactic nuclei from two source samples based on 1) the MOJAVE database and 2) the CGRaBS catalogue, and utilising Fermi-LAT light curves from the public light curve repository. We scan over a wide range of values of the jet-frame time delay $t^{\prime}_{\mathrm{delay}}$ between the neutrino arrival and the time of the prior major $γ$-ray flare and find a pre-trial $\sim 2σ$ correlation at $t^{\prime}_{\mathrm{delay}} \sim 10^{3}$ d, which is consistent ($p_{\mathrm{post-trial}} \sim 0.1$) with expectations under the null hypothesis after trial correction.