2024/08/08 by Andrew J. Long, Long, Andrew J., Enrico D. Schiappacasse +1 · 1 citation
Engineering · Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #Geophysics and Sensor Technology #High Energy Physics - Phenomenology (hep-ph) #Pulsars and Gravitational Waves Research
paper · pdf · doi:10.48550/arxiv.2408.04551
openalex publication_date 2024/08/08 · openalex created_date 2025/01/03 · openalex updated_date 2026/07/28
In the strong magnetic field of a neutron star's magnetosphere, axions coupled to electromagnetism develop a nonzero probability to convert into photons. Past studies have revealed that the axion-photon conversion can be resonantly enhanced. We recognize that the axion-photon resonance admits two parametrically distinct resonant solutions, which we call the mass-matched resonance and the Euler-Heisenberg assisted resonance. The mass-matched resonance occurs at a point in the magnetosphere where the radially-varying plasma frequency crosses the axion mass ωpl ≈ ma. The Euler-Heisenberg assisted resonance occurs where the axion energy satisfies ω≈ (2 ωpl2 / 7 gγγγγ B2 )1/2. This second resonance is made possible though the strong background magnetic field B as well as the nonzero Euler-Heisenberg four-photon self interaction, which has the coupling gγγγγ = 8 α2 / 45 me4. We study the resonant conversion of relativistic axion dark radiation into photons via the Euler-Heisenberg assisted resonance, and we calculate the expected electromagnetic radiation assuming different values for the axion-photon coupling gaγγ and different amplitudes for the axion flux onto the neutron star Φa. We briefly discuss several possible sources of axion dark radiation. Achieving a sufficiently strong axion flux to induce a detectable electromagnetic signal seems unlikely.