The Polarized X-ray Universe: Insights and Discoveries

TL;DR

This paper reviews the significance of X-ray polarization in understanding distant astrophysical sources, discussing physical mechanisms, observational missions, and recent advances in the field.

Contribution

It provides a comprehensive overview of X-ray polarization, including its physical basis, sources, measurement techniques, and recent breakthroughs, highlighting upcoming missions.

Findings

Polarized X-rays reveal internal geometries of astrophysical sources.

Recent missions have advanced the detection of X-ray polarization.

X-ray polarization measurements inform about magnetic fields and particle properties.

Abstract

Polarization is one of the fundamental natures of electromagnetic radiation. The detection of polarization or polarized photons from distant X-ray radiating systems (such as X-ray binaries (XBs), active galactic nuclei (AGN), pulsars, and stars) complements the timing, spectral, and imagining analysis to better understand the physical mechanisms taking place in these sources. Polarization has enhanced the understanding of the internal geometry of these systems and their vicinity. Polarized X-rays can be generated either directly through non-thermal physical processes in the presence of a magnetic field(B) or through the scattering of unpolarized thermal radiation within plasma structures such as an accretion disk. X-ray polarization can measure the two important independent parameters, the polarization degree (PD) and polarization angle (PA) of the X-ray photons. These parameters are crucial as they reveal the characteristics of particles in such a strong magnetic and gravitational field. In this chapter, we have discussed (i) the basic idea of polarization, (ii) some distant sources radiating polarized X-ray photons, (iii) missions dedicated to observing polarized X-ray photons, and (iv) recent breakthroughs and upcoming missions.