2014-2018 multiwavelength obs. of PKS 1502+106

Based on the variability timescale, the physical parameters of the flaring region (e.g., minimum Doppler factor, emission region size, etc.) are constrained. At the peak of the flare, the {gamma}-ray spectrum hardens to {Gamma}_{gamma}_=1.82+/-0.04 and exhibits an obvious curvature/break characteristic that is caused by the typical "cooling break." Modeling of multiband spectral energy distributions reveal a very hard electronic energy spectrum with the electronic spectral index of 1.07+/-0.53.

This result suggests that this fast {gamma}-ray flare may be triggered by magnetic reconnection. (II) During the outburst in 2017, the degree of optical polarization and optical fluxes showed a very tight correlation. By analyzing the Stokes parameters of polarization observations, our results show that this outburst could be triggered by a transverse shock with a compression ratio of {eta}>2.2, and the magnetic field intensity of the shock emission region is about 0.032G.