Supernova bound on keV-mass sterile neutrinos reexamined

Abstract

Active-sterile neutrino mixing is strongly constrained for m_s > 100 keV to avoid excessive energy losses from supernova cores. For smaller m_s, matter effects suppress the effective mixing angle except for a resonant range of energies where it is enhanced. We study the case of ν_tau-ν_s-mixing where a ν_tau-\barν_tau asymmetry builds up due to the strong excess of ν_s over \barν_s emission or vice versa, reducing the overall emission rate. In the warm dark matter range m_s < 10 keV the mixing angle is essentially unconstrained.

6 pages, 4 figures; minor changes, references updated, matches the published version