High-energy neutrinos from blazar flares (INVITED)

The IceCube Collaboration recently reported the observation of a > 290 TeV muon neutrino, IceCube-170922A, coincident with a ~6-month-long γ-ray flare of the blazar TXS 0506+056. The neutrino detection prompted electromagnetic follow-up of the event, and the blazar flare was detected by several instruments, including MAGIC at energies exceeding > 100 GeV. The correlation of the neutrino with the flare of TXS 0506+056 is inconsistent with arising by chance at the 3σ level. An archival search revealed 13 ± 5 further high-energy neutrinos in the direction of TXS 0506+056 during a 6-month period in 2014-2015. These events were not accompanied by a γ-ray flare. Such an accumulation of events is inconsistent with arising from a background fluctuation at the 3.5σ level. Here, recent results on neutrino emission expectations, aimed at interpreting, and motivated by these observations are summarised. The topics briefly reviewed include models of neutrino production in TXS 0506+056 during the 2017 γ-ray flare, during the 2014-2015 period, and expectations of neutrino emission from blazar flares from other sources that occurred in the period 2008-2018 in declinations favourable for detection with IceCube.