Lifting the core-collapse supernova bounds on keV-mass sterile neutrinos

Abstract: We explore the energy and entropy transport as well as the lepton number variation induced from the mixing between electron and sterile neutrinos with keV mass in the supernova core. We develop a radial- and time-dependent treatment of the sterile-electron neutrino mixing, by including ordinary matter effects, reconversions between sterile and electron antineutrinos, as well as the collisional production of sterile particles for the first time. The dynamical feedback due to the production of sterile particles on the composition and thermodynamic properties of the core only leads to major implications for the supernova physics for large mixing angles ($\sin^2 2 \theta > 10^{-10}$). Our findings suggest that a self-consistent appraisal of the electron-sterile conversion physics in the supernova core would relax the bounds on the sterile neutrino mixing parameters reported in the literature for mixing angles smaller than $10^{-6}$, leaving the parameter space of the mass and mixing angles of sterile neutrinos relevant to dark matter searches unconstrained by supernovae.