“Axion-like Particles and Neutron Star Astrophysics”
We discuss modifications to the photon spectrum and polarization due to axion-like particles (ALPs) created in the core of neutron stars. For magnetars, i.e. neutron stars with extreme magnetic fields, ALPs oscillations into photons as they travel through the magnetosphere modify the observed Stokes parameters. We provide simple analytic formulas for the observed Stokes parameters in terms of the ones from background astrophysics, and use the result to put spectral and polarization bounds on the ALP parameter space. For neutron star mergers, ALP decays to photons provide a window into the collision and, along with gravitational wave timing, delineate new physics photon signals from background astrophysics. We discuss constraints obtained from this setup on axion-like particles decaying directly to photons.
Host: Witold Skiba