  While blazars have long been one of the candidates in the search for the
origin of ultra-high energy cosmic rays and astrophysical neutrinos, the BL Lac
object TXS 0506+056 is the first extragalactic source that is correlated with
some confidence with a high-energy neutrino event recorded with IceCube. At the
time of the IceCube event, the source was found in a high state in gamma-rays
with Fermi-LAT and MAGIC. We have explored in detail the parameter space of a
lepto-hadronic radiative model, assuming a single emitting region inside the
relativistic jet. We present the complete range of possible solutions for the
physical conditions of the emitting region and its particle population. For
each solution we compute the expected neutrino rate, and discuss the impact of
this event on our general understanding of emission processes in blazars.
