Sterile neutrino-enhanced supernova explosions

We investigate the enhancement of lepton number, energy, and entropy transport resulting from active-sterile neutrino conversion ${\nu }_e\to {\nu }_s$ deep in the post-bounce supernova core followed by reconversion ${\nu }_s\to {\nu }_e$ further out, near the neutrino sphere. We explicitly take account of shock wave and neutrino heating modification of the active neutrino forward scattering potential which governs sterile neutrino production. We find that the ${\nu }_e$ luminosity at the neutrino sphere could be increased by between $\sim 10\%$ and $\sim 100\%$ during the crucial shock reheating epoch if the sterile neutrino has a rest mass and vacuum mixing parameters in ranges which include those required for viable sterile neutrino dark matter. We also find sterile neutrino transport-enhanced entropy deposition ahead of the shock. This ‘‘preheating” can help melt heavy nuclei and thereby reduce the nuclear photo-dissociation burden on the shock. Both neutrino luminosity enhancement and preheating could increase the likelihood of a successful core collapse supernova explosion.

Figure 1

Right panel shows the core density profile with radius $r$, while the corresponding profiles for MSW resonance energy $E_{\mathrm{res}}$ (solid line) and ${\nu }_e$ chemical potential ${\mu }_{{\nu }_e}$ (dashed line) are shown in the left panel. Here $E_{\mathrm{res}}$ takes its minimum value $E_{\mathrm{res}}^{\min }$ at $r_0$. For a particular neutrino energy, an MSW resonance can occur at two locations (densities), e.g., $r_1$ (${\rho }_1$) and $r_2$ (${\rho }_2$).

Figure 2

Effects of the shock in the interior (curves on the right) and shock-modified ${\nu }_e\to {\nu }_s\to {\nu }_e$ preheating in the outer core (curves on the left). Heavy nucleus mass fraction $X_{\mathrm{H}}$, temperature $k_{\mathrm{B}}T$ (in MeV), and entropy per baryon $S$ (in units of $k_{\mathrm{B}}$) are shown for three different cases. These cases correspond to three different shock strength scenarios with entropy jump (as measured at $\rho =3\times {10}^{13}\mathrm{g}{\mathrm{cm}}^{-3}$) $\Delta S=0.6$ (triangles), $\Delta S=2$ (squares), and $\Delta S=3$ (circles), respectively. Results of the preshock, in-fall one-zone calculation are also included (dotted lines). The minimum of the resonance energy is located around $\rho =7\times {10}^{12}\mathrm{g}{\mathrm{cm}}^{-3}$. This location divides the curves on the left and right, as described in the text.

Figure 3

One-zone calculation results for resonance energy $E_{\mathrm{res}}$ (in MeV) and ${\nu }_e$ chemical potential ${\mu }_{{\nu }_e}$ (Fermi energy, in MeV) are shown as functions of density $\rho$ (in $\mathrm{g}{\mathrm{cm}}^{-3}$). Circles and squares represent $E_{\mathrm{res}}$ and ${\mu }_{{\nu }_e}$, respectively. Filled symbols correspond to the values of these quantities for an assumed strong shock ($\Delta S=3$, as described in Sec. 3). This case includes the effect of ${\nu }_s\to {\nu }_e$ reconversion and associated preheating ahead of the shock, as well as the effect of the shock itself. The effect of post-bounce preheating alone is shown by the quantities with the open circles and squares. For comparison, $E_{\mathrm{res}}$ (dashed line) and ${\mu }_{{\nu }_e}$ (dotted line) are given for the in-fall (preshock, no preheating) case.

Figure 4

Same as Fig. 3, but for the case of a weak shock ($\Delta S=0.6$).