2026/02/13 by Duvier Suarez Fontanella, D. Suárez-Fontanella, M. Ángeles Pérez-García +1
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Dark Matter and Cosmic Phenomena #Pulsars and Gravitational Waves Research #astro-ph.HE #hep-ph
paper · pdf · doi:10.3847/1538-4357/ae8794
published as The Astrophysical Journal, 1006:237 (12pp), 2026 · 13 pages, 5 figures
arxiv created 2026/02/13 · openalex publication_date 2026/07/30 · arxiv updated 2026/07/31 · openalex created_date 2026/07/31 · openalex updated_date 2026/07/31
Abstract We consider the early binary neutron star inspiral phase as a scenario to probe environmental axion–photon resonant conversion. For this we approximately model the merger site electromagnetic fields as the superposition of two rotating dipolar stellar magnetic fields at the 1000 km scale when both magnetospheres are not largely distorted. We capture the time-sliced near-zone magnetospheric geometry relevant for axion–photon mixing. Plasma effects are incorporated through an effective Goldreich–Julian charge density, used to determine the effective plasma frequency and the location of resonant conversion surfaces. Our results show that axion–photon resonant conversion in binary magnetospheres mostly occurs on extended peanut-shaped surfaces whose global geometry evolves as the binary inspiral evolves. The resulting signal is intrinsically narrowband, with photon frequencies set by the axion mass, and its amplitude is slowly modulated by the inspiral through the changing resonant geometry. We illustrate our findings with benchmark values g aγ = 10 −12 GeV −1 and ρ a = 10 23 GeV cm −3 . As an optimistic benchmark, we consider a Galactic source at D = 10 kpc and compare it with a realistic GW170817-like event at D = 40 Mpc. The corresponding D −2 suppression reduces the flux by ∼10 −8 , placing extragalactic signals below the sensitivity of current and planned radio facilities. Our work provides a theoretical and phenomenological framework showing that binary neutron star magnetospheres may support extended resonant axion–photon conversion regions whose geometry and emission correlate with the GW frequency.