The discovery of extraterrestrial very-high-energy neutrinos by the IceCube collaboration has launched a quest for the identification of their astrophysical sources. Gamma-ray blazars have been predicted to yield a cumulative neutrino signal exceeding the atmospheric background above energies of 100 TeV, assuming that both the neutrinos and the γ-ray photons 2 are produced by accelerated protons in relativistic jets. Since the background spectrum falls steeply with increasing energy, the individual events with the clearest signature of being of an extraterrestrial origin are those at PeV energies. Inside the large positional-uncertainty fields of the first two PeV neutrinos detected by IceCube, the integrated emission of the blazar population has a sufficiently high electromagnetic flux to explain the detected IceCube events, but fluences of individual objects are too low to make an unambiguous source association.Here, we report that a major outburst of the blazar PKS B1424−418 occurred in temporal and positional coincidence with the third PeV-energy neutrino event (IC 35) detected by IceCube. Based on an analysis of the full sample of γ-ray blazars in the IC 35 field and assuming a photo-hadronic emission model, we show that the long-term average γ-ray emission of blazars as a class is in agreement with both the measured all-sky flux of PeV neutrinos and the spectral slope of the IceCube signal. The outburst of PKS B1424−418 has provided an energy output high enough to explain the observed PeV event, indicative of a direct physical association.The neutrino excess detected by IceCube comprises 37 events with energies between 30 TeV and 2 PeV, rejecting a purely atmospheric origin at a significance of 5.7 standard deviations [1][2][3] .These events show a broad distribution across both hemispheres of the sky consistent with an extragalactic source population. Due to the very steep background of atmospheric neutrinos, events at PeV energies are best suited for attempting to establish associations with individual blazars. In the first two years of observations, IceCube detected two events with about 1 PeV of deposited energy 1, 2 (IC 14, and IC 20; dubbed 'Bert' and 'Ernie') the diffuse neutrino flux due to the integrated emission of AGN in a given large field at a given time, as well as the maximum possible neutrino flux associated with an individual object of the sample.Blazars are radio-loud AGN with jets oriented close to the line of sight. This substantially increases the apparent brightness of these objects owing to the Doppler boosting of the emission from the relativistically moving emission zones. A direct association of a PeV-neutrino with an * A different analysis of IceCube muon neutrinos finds an excess signal also from the northern sky 14 . † http://pulsar.sternwarte.uni-erlangen.de/tanami 4 individual γ-ray blazar would have the important implication that a sizeable fraction of their observed γ-ray emission must be due to hadronic decays, and that blazar jets are also sources of ultra-high-energy cos...

Supermassive black holes with masses of millions to billions of solar masses are commonly found in the centers of galaxies. Astronomers seek to image jet formation using radio interferometry but still suffer from insufficient angular resolution. An alternative method to resolve small structures is to measure the time variability of their emission. Here we report on gamma-ray observations of the radio galaxy IC 310 obtained with the MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov) telescopes, revealing variability with doubling time scales faster than 4.8 min. Causality constrains the size of the emission region to be smaller than 20% of the gravitational radius of its central black hole.We suggest that the emission is associated with pulsar-like particle acceleration by the electric field across a magnetospheric gap at the base of the radio jet

Supermassive black holes (SMBH) are essential for the production of jets in radio-loud active galactic nuclei (AGN). Theoretical models based on (Blandford & Znajek 1977, MNRAS, 179, 433) extract the rotational energy from a Kerr black hole, which could be the case for NGC 1052, to launch these jets. This requires magnetic fields on the order of 10 3 G to 10 4 G. We imaged the vicinity of the SMBH of the AGN NGC 1052 with the Global Millimetre VLBI Array and found a bright and compact central feature that is smaller than 1.9 light days (100 Schwarzschild radii) in radius. Interpreting this as a blend of the unresolved jet bases, we derive the magnetic field at 1 Schwarzschild radius to lie between 200 G and ∼8.3 × 10 4 G consistent with Blandford & Znajek models.