Active-sterile neutrino oscillations and pulsar kicks

TL;DR

The work develops a magnetized protoneutron star framework for resonant active-sterile neutrino oscillations, introducing a resonance shell that depends on neutrino momentum direction and local medium properties. By analyzing diffusion-driven neutrino flux and the shell geometry, it derives the fractional momentum asymmetry that can drive pulsar kicks, and connects it to a sterile neutrino with keV-scale mass and small mixing angles. Numerical results in two atmospheric models indicate that magnetic fields around ~10^{17} G and sterile neutrino parameters in the keV range can reproduce observed pulsar velocities, while remaining compatible with sterile dark matter hypotheses. The study provides a physically motivated mechanism linking natal kicks, neutrino oscillations in dense magnetized matter, and potential dark matter candidates, with clear predictions for magnetic-field strengths and parameter ranges.

Abstract

We develop a thorough description of neutrino oscillations in a magnetized protoneutron star, based on a resonance layer for neutrinos with different momentum directions. We apply our approach to the calculation of the asymmetry in the neutrino emission during the birth of a neutron star and the pulsar acceleration in the case of an active-sterile neutrino resonant conversion. The observed velocities can be obtained with the magnetic fields expected in the interior of a protoneutron star, for sterile neutrino masses of the order of KeV and small mixing angles.