Journal Article

PUBDB-2026-00739

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Searching for axion dark matter near relaxing magnetars

Roy, S. ; Prabhu, A. ; Thompson, C. ; Witte, S.DESY* ; Blanco, C. ; Zhang, J.

2026
American Physical Society Ridge, NY

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Please use a persistent id in citations: doi:10.1103/glnt-t93q

Report No.: DESY-25-050; arXiv:2505.20450

Abstract: Axion dark matter passing through the magnetospheres of magnetars can undergo hyperefficient resonant mixing with low-energy photons, leading to the production of narrow spectral lines that could be detectable on Earth. Since this is a resonant process triggered by the spatial variation in the photon dispersion relation, the luminosity and spectral properties of the emission are highly sensitive to the charge and current densities permeating the magnetosphere. To date, a majority of the studies investigating this phenomenon have assumed a perfectly dipolar magnetic field structure with a near-field plasma distribution fixed to the minimal charge-separated force-free configuration. While this may be a reasonable treatment for the closed field lines of conventional radio pulsars, the strong magnetic fields around magnetars are believed to host processes that drive strong deviations from this minimal configuration. In this work, we study how realistic magnetar magnetospheres impact the electromagnetic emission produced from axion dark matter. Specifically, we construct charge and current distributions that are consistent with magnetar observations and use these to recompute the prospective sensitivity of radio and submillimeter telescopes to axion dark matter. We demonstrate that the two leading models yield vastly different predictions for the frequency and amplitude of the spectral line, indicating systematic uncertainties in the plasma structure are significant. Finally, we discuss various observational signatures that can be used to differentiate the local plasma loading mechanism of an individual magnetar, which will be necessary if there is hope of using such objects to search for axions.

Note: cc-by, 38 pages, 13 figures

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Contributing Institute(s):

1. Theorie-Gruppe (T)

Research Program(s):

1. DFG project G:(GEPRIS)390833306 - EXC 2121: Das Quantisierte Universum II (390833306) (390833306)
2. 611 - Fundamental Particles and Forces (POF4-611) (POF4-611)

Experiment(s):

1. No specific instrument

Appears in the scientific report 2026

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Database coverage:
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