Axion-neutrino interactions in seesaw models and astrophysical probes

We study axion-neutrino interactions in neutrino-mass extensions of the Standard Model, focusing on the Type-I and inverse seesaw. In these frameworks the effective coupling $g_{aν}$ is tied to the axion scale and can be constrained using existing astrophysical limits on axion couplings to electrons. We then estimate the impact of axion-mediated scattering on neutrino propagation in two benchmarks: resonant interactions with the C$ν$B and scattering on axion dark matter. In the parameter space allowed by current bounds, the resulting optical depths are extremely small, implying no observable signatures with present sensitivities.