Leptohadronic Blazar Models Applied to the 2014–2015 Flare of TXS 0506+056

We investigate whether the emission of neutrinos observed in 2014–2015 from the direction of the blazar TXS 0506+056 can be accommodated with leptohadronic multiwavelength models of the source commonly adopted for the 2017 flare. While multiwavelength data during the neutrino flare are sparse, the large number of neutrino events (13 ± 5) challenges the missing activity in gamma-rays. We illustrate that two to five neutrino events during the flare can be explained with leptohadronic models of different categories: a one-zone model, a compact-core model, and an external radiation field model. If, however, significantly more events were to be accommodated, the predicted multiwavelength emission levels would be in conflict with observational X-ray constraints, or with the high-energy gamma-ray fluxes observed by the Fermi Large Area Telescope, depending on the model. For example, while the external radiation field model can predict up to five neutrino events without violating X-ray constraints, the absorption of high-energy gamma-rays is in minor tension with the data. We therefore do not find any model that can simultaneously explain the high event number quoted by IceCube and the (sparse) electromagnetic data during the neutrino flare.