Work

Pair Cascades in Magnetar Magnetospheres

Year: 2025

Type: article

Abstract: Resonant inverse Compton scattering (RICS) of soft thermal photons by relativistic particles on closed magnetic field loops has been proposed to explain the hard emission observed up to and beyond 200 keV from magnetars. If particles injected at the base of the loops have Lorentz factors ≳102, the RICS spectra will be attenuated by both one-photon pair production and photon splitting in the ultrastrong magnetar fields, producing additional spectral components from pair synchrotron radiation and split photons that produce further generations of pairs and split photons. We investigate such cascades initiated by the primary injected electrons through a Monte Carlo simulation, and study the cascade spectra and pair distributions. For most observer angles, the pair synchrotron and split-photon spectra dominate the RICS primary spectra and produce complex polarization signals. In particular, the synchrotron spectra are highly polarized with degree 40%–80%, are softer than the RICS spectra, and may account for the high polarization of some magnetar spectra observed by the Imaging X-ray Polarimetry Explorer above 3 keV.

Source: The Astrophysical Journal

DOI: 10.3847/1538-4357/adfa06

Authors: Alice K. Harding, Zorawar Wadiasingh, Matthew G. Baring

Institutions: Los Alamos National Laboratory, Goddard Space Flight Center, University of Maryland, College Park, Rice University

Language: English

Topic: Astrophysics and Cosmic Phenomena

Subfield: Nuclear and High Energy Physics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $4,499

Funders: U.S. Department of Energy, National Aeronautics and Space Administration, National Energy Research Scientific Computing Center