Enhanced neutrino emissivities in pseudoscalar-mediated Dark Matter annihilation in Neutron Stars

We calculate neutrino emissivities from self-annihilating dark matter ($\chi$) in the dense and hot stellar interior of a (proto)neutron star. Using a model where dark matter interacts with nucleons in the stellar core through a pseudoscalar boson ($a$) we find that the neutrino production rates from the dominant reaction channels $\chi \chi \rightarrow \nu \bar{\nu}$ or $\chi \chi \rightarrow a a$, with subsequent decay of the mediator $ a \rightarrow \nu \bar{\nu}$, could locally match and even surpass those of the standard neutrinos from the modified nuclear URCA processes at early ages. We find that the emitting region can be localized in a tiny fraction of the star (less than a few percent of the core volume) and the process can last its entire lifetime for some cases under study. We discuss the possible consequences of our results for stellar cooling in light of existing dark matter constraints.