We investigate matter-enhanced Mikheyev-Smirnov-Wolfenstein (MSW) active-sterile neutrino conversion in the ${\nu }_e\rightleftharpoons {\nu }_s$ channel in the collapse of the iron core of a presupernova star. For values of sterile neutrino rest mass $m_s$ and vacuum mixing angle $\theta$ (specifically, $0.5\mathrm{keV}<m_s<10\mathrm{keV}$ and ${sin}^{2}2\theta >5\times {10}^{-12}$) which include those required for viable sterile neutrino dark matter, our one-zone in-fall phase collapse calculations show a significant reduction in core lepton fraction. This would result in a smaller homologous core and therefore a smaller initial shock energy, disfavoring successful shock reheating and the prospects for an explosion. However, these calculations also suggest that the MSW resonance energy can exhibit a minimum located between the center and surface of the core. In turn, this suggests a post-core-bounce mechanism to enhance neutrino transport and neutrino luminosities at the core surface and thereby augment shock reheating: (1) scattering-induced or coherent MSW ${\nu }_e\to {\nu }_s$ conversion occurs deep in the core, at the first MSW resonance, where ${\nu }_e$ energies are large ($\sim 150\mathrm{MeV}$); (2) the high energy ${\nu }_s$ stream outward at near light speed; (3) they deposit their energy when they encounter the second MSW resonance ${\nu }_s\to {\nu }_e$ just below the proto-neutron star surface.

• Received 14 September 2006

DOI:https://doi.org/10.1103/PhysRevD.74.125015