| High-energy neutrino emission of radio-loud active galactic nuclei |
| Emma Kun |
| Konkoly Observatory, CSFK, Hungary |
| Relativistic jets in radio-loud active galactic nuclei (AGN) are the most powerful (persistent) particle accelerators in the universe, and they are emerging as strong sources of high-energy (HE) neutrino emission. Recent models suggest the cosmic-ray-induced HE neutrino production in AGN should be beamed, therefore those classes of AGN that launch their radio jet close to our line-of-sight, the blazars and quasars, are particular sources of interest. In 2018 the IceCube Collaboration with partner observatories on Earth and in space has been reported on the multimessenger observations of the gamma-ray flaring blazar TXS 0506+056 (recently re-classified as an FSRQ), and identified this AGN as the origin of neutrino IceCube-170922A. We reported on the radio brightening of this AGN at 15 GHz preceding the detection of the IceCube-neutrino, which was similar to what we already reported for the blazar PKS 0723-008 at 15 GHz and IceCube event ID5. The most recent neutrino candidate AGN, FSRQ PKS 1502+106 had its highest single-dish flux density at 15 GHz when the corresponding HE neutrino was detected, increasing the number of AGN behaving on this way to three. Although this number is rather small, even if we consider that the total number of HE neutrinos observed by IceCube is a bit more than 100, these simultaneous detections raise the question: do the HE neutrinos and the enhanced radio radiation share the same emission site in AGN? We demonstrate that given its exceptional resolution, very long baseline interferometry can help us to locate possible emission sites in AGN jets. |