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Vacuum polarization effects in baryon-loaded magnetar bursts and implications for x-ray polarization

Tomoki Wada*

  • *Contact author: tomoki.wada@astr.tohoku.ac.jp
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Phys. Rev. D 112, 123027 – Published 15 December, 2025

DOI: https://doi.org/10.1103/k3hz-k6v4

Abstract

Magnetars provide natural laboratories for strong-field quantum electrodynamics processes, such as vacuum polarization, which gives rise to vacuum resonance together with the plasma response. We develop a general framework to describe vacuum resonance in a three-component plasma consisting of ions, electrons, and positrons, as expected in baryon-loaded magnetar bursts. By introducing a parametrization of the plasma composition, we establish the general criterion for the occurrence of vacuum resonance in such plasmas. Our analysis encompasses both Mikheyev-Smirnov-Wolfenstein-like adiabatic mode conversion and nonadiabatic eigenmode transition, highlighting their dependence on the plasma composition. Applying this framework to baryon-loaded fireballs in magnetar bursts, we estimate the characteristic x-ray polarization signatures. Detection of these polarizations will provide observational signatures of vacuum polarization as well as baryon loading in magnetar fireballs.

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Phys. Rev. D 112, 123027– Published 15 December, 2025
  • Received 2 September 2025
  • Revised 5 November 2025
  • Accepted 7 November 2025
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