Probing axion-like particles with multimessenger observations of neutron star mergers
Francesca Lecce, Alessandro Lella, Giuseppe Lucente, Vimal Vijayan, Andreas Bauswein, Maurizio Giannotti, Alessandro Mirizzi
arXiv:2504.02032v2 Announce Type: replace-cross
Abstract: Axion-like particles (ALPs) can be copiously produced in binary neutron star (BNS) mergers through nucleon-nucleon bremsstrahlung if the ALP-nucleon couplings $g_{a N}$ are sizable. The ALP-photon coupling $g_{agamma}$ may trigger conversions of ultralight ALPs into photons in the magnetic fields of the merger remnant and of the Milky Way. This effect would lead to a potentially observable short gamma-ray signal, in coincidence with the gravitational-wave signal produced during the merging process. This event could be detected through multi-messenger observation of BNS mergers employing the synergy between gravitational-wave detectors and gamma-ray telescopes. Here, we study the sensitivity of current and proposed MeV gamma-ray experiments to detect such a signal. As an explicit example, we consider ALP couplings related as in the Kim-Shifman-Vainshtein-Zakharov (KSVZ) axion model, and show that in this case the proposed instruments can reach a sensitivity down to $g_{agamma}gtrsim textrm{few} times 10^{-13},text{GeV}^{-1}$ for $m_a lesssim 10^{-9}$ eV, comparable with the SN 1987A limit.arXiv:2504.02032v2 Announce Type: replace-cross
Abstract: Axion-like particles (ALPs) can be copiously produced in binary neutron star (BNS) mergers through nucleon-nucleon bremsstrahlung if the ALP-nucleon couplings $g_{a N}$ are sizable. The ALP-photon coupling $g_{agamma}$ may trigger conversions of ultralight ALPs into photons in the magnetic fields of the merger remnant and of the Milky Way. This effect would lead to a potentially observable short gamma-ray signal, in coincidence with the gravitational-wave signal produced during the merging process. This event could be detected through multi-messenger observation of BNS mergers employing the synergy between gravitational-wave detectors and gamma-ray telescopes. Here, we study the sensitivity of current and proposed MeV gamma-ray experiments to detect such a signal. As an explicit example, we consider ALP couplings related as in the Kim-Shifman-Vainshtein-Zakharov (KSVZ) axion model, and show that in this case the proposed instruments can reach a sensitivity down to $g_{agamma}gtrsim textrm{few} times 10^{-13},text{GeV}^{-1}$ for $m_a lesssim 10^{-9}$ eV, comparable with the SN 1987A limit.

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