Testing High-Energy Emission Models for Blazars with X-ray Polarimetry

TL;DR

This study predicts X-ray polarization signatures in blazars to distinguish between leptonic and hadronic emission models, highlighting the potential for upcoming telescopes to detect these signals during flaring states.

Contribution

It introduces a multizone polarized leptonic jet model to predict X-ray polarization in blazars, aiding in differentiating emission mechanisms with future observations.

Findings

Significant polarization detection possible in flaring states for some blazars.

Proton synchrotron emission may be marginally detectable during flares.

Next-generation telescopes are needed for confident SSC polarization measurements.

Abstract

Both leptonic and hadronic emission processes may contribute to blazar jet emission; which dominates in blazars's high energy emission component remains an open question. Some intermediate synchrotron peaked blazars transition from their low to high energy emission components in the X-ray band making them excellent laboratories to probe both components simultaneously, and good targets for the newly launched Imaging X-ray Polarimetry Explorer. We characterize the spectral energy distributions for three such blazars: CGRaBS~J0211+1051, TXS~0506+056, and S5~0716+714, predicting their X-ray polarization behavior by fitting a multizone polarized leptonic jet model. We find that a significant detection of electron synchrotron dominated polarization is possible with a 300~ks observation for S5~0716+714 and CGRaBS~J0211+1051 in their flaring states, while even 500~ks observations are unlikely to measure synchrotron self-Compton polarization. Importantly, non-leptonic emission processes like proton synchrotron are marginally detectable for our brightest ISP, S5~0716+714, during a flaring state. Improved {\it IXPE} data reduction methods or next generation telescopes like {\it eXTP} are needed to confidently measure SSC polarization.