Prospects for Detecting X-ray Polarization in Blazar Jets

Abstract

X-ray polarization should provide new probes of magnetic field geometry and acceleration physics near the base of blazar jets, but near-future missions will have limited sensitivity. We thus use existing lower energy data and X-ray variability measurements in the context of a basic synchro-Compton model to predict the X-ray polarization level and the probability of detection success for individual sources, listing the most attractive candidates for an IXPE campaign. We find that, as expected, several high-peak blazars such as Mrk 421 can be easily measured in 100 ksec exposures. Most low peak sources should only be accessible to triggered campaigns during bright flares. Surprisingly, a few intermediate peak sources can have anomalously high X-ray polarization and thus are attractive targets.