Probing axionlike particles with multimessenger observations of neutron star mergers

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_𝑎⁢𝛾 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 multimessenger 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 axion model, and show that in this case the proposed instruments can reach a sensitivity down to 𝑔_𝑎⁢𝛾 ≳ few ×10⁻¹³ GeV⁻¹ for 𝑚_𝑎 ≲ 10⁻⁹ eV, comparable with the SN 1987A limit.. Authors: Lecce, Francesca [Dipartimento Interateneo di Fisica “Michelangelo Merlin", Bari (Italy); Istituto Nazionale di Fisica Nucleare - Sezione di Bari (Italy)] (ORCID:0009000969675042); Lella, Alessandro [Dipartimento Interateneo di Fisica “Michelangelo Merlin", Bari (Italy); Istituto Nazionale di Fisica Nucleare - Sezione di Bari (Italy)] (ORCID:0000000232663154); Lucente, Giuseppe [SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)]; Vijayan, Vimal [GSI-Helmholtzzentrum fur Schwerionenforschung, Darmstadt (Germany)] (ORCID:0000000246902515); Bauswein, Andreas [GSI-Helmholtzzentrum fur Schwerionenforschung, Darmstadt (Germany)] (ORCID:0000000167983572). DOE Contract: AC02-76SF00515. Subjects: Axion-like particles; Axions; Binary stars; Neutron stars & pulsars