Abstract
ABSTRACT Polarization offers a unique view in the physical processes of astrophysical jets. We report on optical circular polarization (CP) observations of two famous blazars, namely 3C 279 and PKS 1510−089, at high linearly polarized states. This is the first time PKS 1510−089 is observed in optical CP. While only upper limits can be extracted from our observing campaign, the non-detection of optical CP allows us to provide meaningful constraints on their magnetic field strength and jet composition. We find that high-energy emission models requiring high magnetic field strength and a low positron fraction can be excluded.
Highlights
Polarization is a powerful tool to understand the magnetic field structure and evolution in black hole jets (Blandford et al 2019; Hovatta & Lindfors 2019)
We report on optical circular polarization observations of two famous blazars, namely 3C 279 and PKS 1510−089, at high linearly polarized states
While only upper limits can be extracted from our observing campaign, the non-detection of optical circular polarization allows us to provide meaningful constraints on their magnetic field strength and jet composition
Summary
Polarization is a powerful tool to understand the magnetic field structure and evolution in black hole jets (Blandford et al 2019; Hovatta & Lindfors 2019). Due to the synchrotron nature of their radiation, blazars are highly polarized and show variable, and often quite peculiar, polarization behavior. This behavior is connected to their high-energy emission (Blinov et al 2018), the origin of which is still a mystery. The main mechanisms invoked to explain the high-energy emission in blazar jets are inverse-Compton scattering of relativistic electrons ( known as leptonic processes) by either internal (SSC) or external (EC) photon fields, and proton synchrotron, Bethe-Heitler pair production, pion decay etc. Assuming an intrinsic CP signal exists, we use the detected upper limits in combination with their linear polarization degree to constrain their magnetic field strength and jet composition
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