Radiation and Polarization Signatures from Magnetic Reconnection in Relativistic Jets. II. Connection with γ-Rays

It is commonly believed that blazar jets are relativistic magnetized plasma outflows from supermassive black holes. One key question is how the jets dissipate magnetic energy to accelerate particles and drive powerful multiwavelength flares. Relativistic magnetic reconnection has been proposed as the primary plasma physical process in the blazar emission region. Recent numerical simulations have shown strong acceleration of nonthermal particles that may lead to multiwavelength flares. Nevertheless, previous works have not directly evaluated gamma-ray signatures from first-principles simulations. In this paper, we employ combined particle-in-cell and polarized radiation transfer simulations to study multiwavelength radiation and optical polarization signatures under the leptonic scenario from relativistic magnetic reconnection. We find harder-when-brighter trends in optical and Fermi-LAT gamma-ray bands as well as closely correlated optical and gamma-ray flares. The swings in optical polarization angle are also accompanied by gamma-ray flares with trivial time delays. Intriguingly, we find highly variable synchrotron self-Compton signatures due to inhomogeneous particle distributions during plasmoid mergers. This feature may result in fast gamma-ray flares or orphan gamma-ray flares under the leptonic scenario, complementary to the frequently considered minijet scenario. It may also imply neutrino emission with low secondary synchrotron flux under the hadronic scenario, if plasmoid mergers can accelerate protons to very high energy.

Automated summary

This study investigates the multiwavelength radiation and optical polarization signatures in relativistic magnetic reconnection using particle-in-cell and polarized radiation transfer simulations. The study finds a correlation between the brightness and hardness in optical and Fermi-LAT gamma-ray bands, as well as a close relationship between optical and gamma-ray flares. The study also discovers highly variable synchrotron self-Compton signatures during plasmoid mergers. These findings provide important insights into the physical processes of blazar jets.