Recently the IceCube collaboration detected very high energy ( VHE ) neutrinos and associated them with the blazar TXS 0506+056 , raising a possible association of VHE neutrinos with this and other individual blazars .
Very Long Baseline Interferometry ( VLBI ) is so far the only technique enabling the imaging of the innermost jet at milli-arcsec resolution ( parsec scale ) , where the high energy emission possibly originates from .
Here , we report on the radio properties of the parsec scale jet in TXS 0506+056 derived from the analysis of multi-epoch multi-frequency archive VLBI data .
The half opening angle of the jet beam is about 3.8 \degr , and the jet inclination angle is about 20 \degr .
The overall jet structure shows a helical trajectory with a precessing period of 5–6 years , likely originating from instabilities operating at parsec scales .
The calculated beaming parameters ( Doppler boosting factor , bulk Lorentz factor ) suggest a moderately relativistic jet .
The pc-scale magnetic field strength is estimated in the contexts of core-shift and variability , and is in general agreement in the range of 0.2 - 0.7 G. And it is found to decrease from a relatively larger value during the quiescent period before the ongoing flare .
This suggests a conversion of magnetic field energy density to particle energy density that help accelerate injected particles at the jet base and result in variable shocked emission .
The neutrino event could be associated with the onset of energetic particle injection into the jet .
This scenario then supports the lepto-hadronic origin of the VHE neutrinos and \gamma -ray emission owing to a co-spatial origin .