Misaligned BL Lac object 3C 371

We then used this set of parameters to interpret the source MWL behaviour, modelling its broadband spectral energy distribution (SED) with theoretical blazar emission scenarios. The MWL variability of the source in the UV, X-ray, and gamma-ray bands is comparable to that in optical, especially considering the lower coverage of the first two wavebands. On the other hand, the radio bands show variability of much lower magnitude.

Moreover, this MWL emission shows a high degree of correlation, which is compatible with zero lag, again with the exception of the radio emission. The radio VLBI images reveal super-luminal motion of one of the identified components, which we used to set constraints on the jet kinematics and parameters, and to estimate a viewing angle of {GAMMA}=(9.6+/-1.6){deg}, a Doppler factor of {delta}=6.0+/-1.1, and a Lorentz factor of {GAMMA}=6.0+/-1.8.

The polarised radio emission was found to be anti-correlated with the total flux, and to follow the same behaviour as the polarised optical radiation. The optical-UV spectral behaviour shows a mild harder-when-brighter trend on long timescales, and other trends such as redder-when-brighter on shorter timescales. We successfully modelled the broadband emission with a leptonic scenario, where we compared the low and high emission states during the period of complete MWL coverage.

The difference between these two states can be ascribed mainly to a hardening of the distribution of particles. The derived features of the source confirm that 3C 371 is a BL Lac whose jet is not well aligned with the line of sight.