The Blazar 3C 66A in 2003-2004: hadronic versus leptonic model fits

The low‐frequency peaked BL Lac object 3C 66A was the subject of an extensive multi‐wavelength campaign from July 2003 till April 2004, which included quasi‐simultaneous observations at optical, X‐rays and very high energy gamma‐rays. Here we apply the hadronic Synchrotron‐Proton Blazar (SPB) model to the observed spectral energy distribution time‐averaged over a flaring state, and compare the resulting model fits to those obtained from the application of the leptonic Synchrotron‐Self‐Compton (SSC) model. The results are used to identify diagnostic key predictions of the two blazar models for future multi‐wavelength observations.