Neutron stars as photon double-lenses: Constraining resonant conversion into ALPs

Kyrylo Bondarenko, Alexey Boyarsky, Josef Pradler, Anastasia Sokolenko (Corresponding author)

Publications: Contribution to journalArticlePeer Reviewed


Axion-photon conversion is a prime mechanism to detect axion-like particles that share a coupling to the photon. We point out that in the vicinity of neutron stars with strong magnetic fields, magnetars, the effective photon mass receives comparable but opposite contributions from free electrons and the radiation field. This leads to an energy-dependent resonance condition for conversion that can be met for arbitrary light axions and leveraged when using systems with detected radio component. Using the magnetar SGR J1745-2900 as an exemplary source, we demonstrate that sensitivity to |gaγ|∼10−12GeV−1 or better can be gained for ma≲10−6eV, with the potential to improve current constraints on the axion-photon coupling by more than one order of magnitude over a broad mass range. With growing insights into the physical conditions of magnetospheres of magnetars, the method hosts the potential to become a serious competitor to future experiments such as ALPS-II and IAXO in the search for axion-like particles.
Original languageEnglish
Article number138238
Number of pages7
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Publication statusPublished - 10 Nov 2023

Austrian Fields of Science 2012

  • 103012 High energy physics


  • Axion-like particle
  • Axion-photon resonant conversion
  • Magnetar

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