Sterile Neutrino-Enhanced Supernova Explosions

TL;DR

The paper investigates how active-sterile-active neutrino flavor transformations in a core-collapse supernova can enhance energy and lepton-number transport, potentially aiding shock revival. By incorporating shock-induced modifications to the forward-scattering potential and analyzing both in-fall and post-bounce phases, it shows that sterile neutrinos with keV-scale masses and small vacuum mixing can mediate substantial transport and pre-heating, increasing the electron-neutrino luminosity near the neutrino sphere by roughly 10–100% during the crucial shock-reheating epoch. It also demonstrates a pre-heating mechanism ahead of the shock that can melt heavy nuclei, reducing the photo-dissociation burden and promoting explosion conditions, with energy deposition estimates suggesting substantial impact near the neutrino sphere. The work highlights a narrow but physically motivated region of sterile-neutrino parameter space that overlaps viable dark matter candidates, while underscoring the need for full multi-dimensional hydrodynamics and detailed neutrino transport to quantify the effects in realistic supernova models.

Abstract

We investigate the enhancement of lepton number, energy, and entropy transport resulting from active-sterile neutrino conversion $ν_e\toν_s$ deep in the post-bounce supernova core followed by re-conversion $ν_s\toν_e$ 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 $ν_e$ luminosity at the neutrino sphere could be increased by between $\sim 10 %$ and $\sim 100 %$ during the crucial shock re-heating 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 `` pre-heating\rq\rq can help melt heavy nuclei and thereby reduce the nuclear photo-dissociation burden on the shock. Both neutrino luminosity enhancement and pre-heating could increase the likelihood of a successful core collapse supernova explosion.

Figures (4)

• Figure 1: Right panel shows the core density profile with radius $r$, while the corresponding profiles for MSW resonance energy $E_{\rm res}$ (solid) and $\nu_e$ chemical potential $\mu_{\nu_e}$ (dashed) are shown in the left panel. Here $E_{\rm res}$ takes its minimum value $E_{\rm res}^{\rm min}$ 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 $\nu_e\rightarrow\nu_s\rightarrow\nu_e$ pre-heating in the outer core (curves on the left). Heavy nucleus mass fraction $X_{\rm H}$, temperature $k_{\rm B} T$ (in MeV), and entropy per baryon $S$ (in units of $k_{\rm B}$) are shown for three different cases. These cases correspond to three different shock strength scenarios with entropy jump (as measured at $\rho=3\times{10}^{13}\,{\rm g}\,{\rm cm}^{-3}$) $\Delta S =0.6$ (triangles), $\Delta S =2$ (squares), and $\Delta S =3$ (circles), respectively. Results of the pre-shock, in-fall one-zone calculation are also included (dotted lines). The minimum of the resonance energy is located around $\rho=7\times 10^{12}\, {\rm g}\,{\rm cm}^{-3}$. This location divides the curves on the left and right, as described in the text.
• Figure 3: One-zone calculation results for resonance energy $E_{res}$ (in MeV) and $\nu_e$ chemical potential $\mu_{\nu_e}$ (Fermi energy, in MeV) are shown as functions of density $\rho$ (in ${\rm g}\,{\rm cm}^{-3}$). Circles and squares represent $E_{\rm res}$ 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 Section III). This case includes the effect of $\nu_s\rightarrow\nu_e$ reconversion and associated pre-heating ahead of the shock, as well as the effect of the shock itself. The effect of post-bounce pre-heating alone is shown by the quantities with the open circles and squares. For comparison, $E_{\rm res}$ (dashed line) and $\mu_{\nu_e}$ (dotted line) are given for the in-fall (pre-shock, no pre-heating) case.
• Figure 4: Same as Fig.3, but for the case of a weak shock ($\Delta S = 0.6$).