High Energy Polarization of Blazars : Detection Prospects

Abstract

Emission from blazar jets in the ultraviolet, optical, and infrared is polarized. If these low-energy photons were inverse-Compton scattered, the upscattered high-energy photons retain a fraction of the polarization. Current and future X-ray and gamma-ray polarimeters such as INTEGRAL-SPI, PoGOLITE, X-Calibur, Gamma-Ray Burst Polarimeter, GEMS-like missions, ASTRO-H, and POLARIX have the potential to discover polarized X-rays and gamma-rays from blazar jets for the first time. Detection of such polarization will open a qualitatively new window into high-energy blazar emission; actual measurements of polarization degree and angle will quantitatively test theories of jet emission mechanisms. We examine the detection prospects of blazars by these polarimetry missions using examples of 3C 279, PKS 1510-089, and 3C 454.3, bright sources with relatively high degrees of low-energy polarization. We conclude that while balloon polarimeters will be challenged to detect blazars within reasonable observational times (with X-Calibur offering the most promising prospects), space-based missions should detect the brightest blazars for polarization fractions down to a few percent. Typical flaring activity of blazars could boost the overall number of polarimetric detections by nearly a factor of five to six purely accounting for flux increase of the brightest of the comprehensive, all-sky, Fermi-LAT blazar distribution. The instantaneous increase in the number of detections is approximately a factor of two, assuming a duty cycle of 20% for every source. The detectability of particular blazars may be reduced if variations in the flux and polarization fraction are anticorrelated. Simultaneous use of variability and polarization trends could guide the selection of blazars for high-energy polarimetric observations.

Matches published version in ApJ

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Cited by in corpus (5)

• $\gamma$-ray polarimetry with conversions to $e^{+}{e}^{-}$ pairs: polarization asymmetry and the way to measure it
• Monte-Carlo Applications for Partially Polarized Inverse External-Compton Scattering (MAPPIES) II -- Application to the UV/Soft X-ray Excess in Blazar Spectra
• MeV-GeV Polarimetry with $\gamma \to e^{+}{e}^{-}$: Asserting the Performance of Silicon Strip Detectors-Based Telescopes
• High-Energy Polarization: Scientific Potential and Model Predictions
• e-ASTROGAM mission: a major step forward for gamma-ray polarimetry