Scientific Prospects for Hard X-ray Polarimetry

TL;DR

Hard X-ray polarimetry offers new insights into high-energy astrophysical sources and fundamental physics, with technological advancements enabling effective measurements in the >10 keV range.

Contribution

This paper reviews scientific motivations for hard X-ray polarimetry and evaluates four innovative polarimeter designs through simulations for space missions.

Findings

Four polarimeter designs analyzed for performance

Simulations show feasibility for science goals

Instrument requirements matched with science objectives

Abstract

X-ray polarimetry promises to give qualitatively new information about high-energy sources. Examples of interesting source classes are binary black hole systems, rotation and accretion powered neutron stars, Microquasars, Active Galactic Nuclei and Gamma-Ray Bursts. Furthermore, X-ray polarimetry affords the possibility for testing fundamental physics, e.g. to observe signatures of light bending in the strong gravitational field of a black hole, to detect third order Quantum Electrodynamic effects in the magnetosphere of Magnetars, and to perform sensitive tests of Lorentz Invariance. In this paper we discuss scientific drivers of hard (>10 keV) X-ray polarimetry emphasizing how observations in the hard band can complement observations at lower energies (0.1 - 10 keV). Subsequently, we describe four different technical realizations of hard X-ray polarimeters suitable for small to medium sized space borne missions, and study their performance in the signal-dominated case based on Monte Carlo simulations. We end with confronting the instrument requirements for accomplishing the science goals with the capabilities of the four polarimeters.