Abstract
Blazars have long been considered as accelerator candidates for cosmic rays. In such a scenario, hadronic interactions in the jet would produce neutrinos and gamma rays. Correlating the astrophysical neutrinos detected by IceCube with the gamma-ray emission from blazars could therefore help elucidate the origin of cosmic rays. In our method we focus on periods where blazars show an enhanced gamma-ray flux, as measured by Fermi-LAT, thereby reducing the background of the search. We present results for TXS 0506+056, using nearly 10 years of IceCube data and discuss them in the context of other recent analyses on this source. In addition, we give an outlook on applying this method in a stacked search for the combined emission from a selection of variable Fermi blazars.
Highlights
Blazars are a promising class of potential cosmic-ray accelerators and neutrino sources
The coincidence between a single Extremely High Energy (EHE) neutrino registered by IceCube on September 22nd 2019 and a blazar flare from TXS 0506+056 [6] could be the first evidence for a astrophysical neutrino source
From the lightcurve LC(t) it derives a signal time probability distribution function (PDF), which gets combined with the point spread function (PSF) and energy PDF p(E) to define the signal term S in the likelihood: S(x, E, t; γ, Φ0) = PSF(x) × p(E) × max {0, (LC(t) − Φ0) /norm}. x, E, and t are respectively the spatial coordinates, energy, and arrival time of a given neutrino event
Summary
Blazars are a promising class of potential cosmic-ray accelerators and neutrino sources. The 2017 flare began several months prior to the neutrino event and the same blazar was active in the years before. Similar analyses have been performed on other blazars individually [7], the method had not yet been used in the kind of stacking analyses which are the most powerful probes of the contribution of blazars to the astrophysical neutrino flux [8]. In this contribution we present such a combined analysis which could provide stronger limits, or a discovery
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