Gamma-Ray Pair Regime Polarimetry with AMEGO-X

Abstract

Many astrophysical sources such as gamma-ray bursts, active galactic nuclei (AGN), and pulsars emit high-energy radiation in the form of gamma rays. Gamma-ray polarimetry can reveal critical information about their emission mechanisms, which may be otherwise unattainable. The All-sky Medium Energy Gamma-ray Observatory eXplorer (AMEGO-X) is a proposed NASA mission concept designed to detect gamma rays from extreme cosmic sources in the 100 keV to 1 GeV range. Above 10 MeV, gamma rays interacting with the detector primarily undergo pair production, converting into an electron and positron. The azimuthal angle of these two particles carries information about the gamma ray's initial linear polarization. However, multiple scattering of the electron and positron in the detector material is a fundamental limitation and the primary source of polarization sensitivity loss. To evaluate AMEGO-X's ability to measure polarization, Monte Carlo simulations of polarized gamma rays and dedicated data analysis software are used to study the instrument's response. This research presents preliminary simulations that include realistic detector effects to assess the response of AMEGO-X to polarized gamma rays. These results support future advances in high-energy gamma-ray polarimetry.