Presentation #109.03 in the session “Multi-Messenger Astrophysics (Session)”.
Blazars are relativistic jets from supermassive black holes that point very close to our line of sight. They are among the most powerful cosmic particle accelerators, which are known to exhibit highly variable multi-wavelength flaring activities. Recent detection of a very high energy neutrino event by IceCube that was coincident with the blazar TXS 0506+056 Fermi gamma-ray flare strongly suggests that blazars can be the extragalactic cosmic rays and neutrinos. Spider pulsars are millisecond pulsars in a compact binary system with a low-mass companion star. They are excellent galactic laboratories for particle acceleration in magnetized relativistic outflows. Although the two types of systems are widely different in physical scales, they are both magnetized plasma in extreme environment, in which magnetic dissipation is crucial to the particle acceleration. High-energy polarization can be ideal diagnostic of the magnetic field morphology and evolution for these systems. Here we present detailed numerical simulations of X-ray and MeV gamma-ray polarization signatures arising from these two systems. We find that high-energy polarization can unambiguously identify cosmic ray acceleration and neutrino production in blazars. For spider pulsars, high-energy polarization can probe the magnetic field morphology, which are crucial for the study of pulsar wind and particle acceleration therein. Future missions such as IXPE and AMEGO-X can unveil rich physics in these systems with their high-energy polarimetry capability.