VLBI analysis of a potential high-energy neutrino emitter blazar, CTD74

Recent studies suggest that high-energy neutrinos can be produced in the jets of blazars, radio-loud active galactic nuclei (AGN) with jets pointing close to the line of sight. Follow-up of possible high-energy neutrino counterpart objects is essential in the electromagnetic regime due to the relatively poor angular resolution of current neutrino detectors. Since the Very Long Baseline Interferometry (VLBI) technique provides the highest angular resolution to study the radio jets of blazars, a growing number of investigations are conducted to connect individual blazars to given high-energy neutrino events. We analysed more than 20 years of available archival VLBI data of the blazar CTD 74, which has been listed as a possible counterpart of the neutrino event EHEA2012-05-23. Using cm-wavelength data, we studied the apparent speed of jet components, and we investigated the jet structure and core flux density before and after the neutrino event. Our results indicate a significant brightening of the core after the neutrino event.