Speaker
Description
Axion-like particles (ALPs) can be copiously produced in binary neutron star (BNS) mergers via nucleon-nucleon bremsstrahlung, provided the ALP-nucleon coupling $g_{aN}$ is sufficiently large. If ALPs also couple to photons through the coupling $g_{a\gamma}$, they can convert into gamma rays in the presence of strong magnetic fields, such as those surrounding the merger remnant and in the Milky Way. This process could generate a short gamma-ray burst coincident with the gravitational-wave signal from the merger, offering a novel multi-messenger signature of ALPs.
In this talk, I will present a study of the sensitivity of current and proposed MeV gamma-ray instruments to detect such a signal. I will show that future detectors could probe photon couplings down to $g_{a\gamma} \gtrsim \text{few} \times 10^{-13}\,\text{GeV}^{-1}$ for ultralight ALPs with $m_a \lesssim 10^{-9}~\text{eV}$ comparable to constraints from SN~1987A. These results highlight the exciting potential of combining gravitational-wave and gamma-ray observations to search for new physics in the ALP sector.
