Pre-Supernova (Anti)Neutrino Emission Due to Weak-Interaction Reactions with Hot Nuclei

TL;DR

This work tackles the problem of predicting pre-supernova (anti)neutrino spectra, crucial for detection prospects, by comparing a thermodynamically consistent Thermal Quasiparticle Random-Phase Approximation (TQRPA) treatment of Gamow--Teller transitions with the conventional effective $Q$-value method using MESA-derived stellar trajectories. The method incorporates nuclear de-excitation and thermally excited states, leading to higher energy luminosities and harder spectra than the $Q_\mathrm{eff}$ approach, particularly for $\nu_e$ via downward transitions and for $\bar{\nu}_e$ when ND is significant. Neutrino oscillations are shown to reshape Earth-bound fluxes, with NH substantially suppressing $\nu_e$ and IH more strongly suppressing $\bar{\nu}_e$, while the ND channel can amplify high-energy tails in certain IH scenarios. The results have direct implications for the detectability of pre-supernova neutrinos and guide future studies on detection channels and oscillation effects in these stellar environments.

Abstract

Reliable predictions of (anti)neutrino spectra and luminosities are essential for assessing the feasibility of detecting pre-supernova neutrinos. Using the stellar evolution code MESA, we calculate the (anti)neutrino spectra and luminosities under realistic conditions of temperature, density, and electron fraction. Our study includes (anti)neutrinos produced by both thermal processes and nuclear weak-interaction reactions. By comparing the results of the thermal quasiparticle random-phase approximation with the standard technique based on the effective $Q$-value method, we investigate how thermal effects influence the spectra and luminosities of emitted (anti)neutrinos. Our findings show that a thermodynamically consistent treatment of Gamow--Teller transitions in hot nuclei enhances both the energy luminosity and the average energies of the emitted (anti)neutrinos.

Figures (6)

• Figure 1: The trajectory in the plane central temperature $T_c$ and central density $\rho_c$. The open circles correspond to the points at which the (anti)neutrino luminosities were calculated. For each point we indicate the time $t$ to collapse.
• Figure 2: Time evolution of the nuclear contributions to $\nu_e$ and $\bar{\nu}_e$ luminosities computed employing the TQRPA and $Q_\mathrm{eff}$ approaches. For $\bar{\nu}_e$ we also show the luminosity without the ND contribution.
• Figure 3: Time evolution of the total $\bar{\nu}_e$ and $\nu_{\mu,\,\tau}$, $\bar{\nu}_{\mu,\,\tau}$ luminosities computed employing the TQRPA and $Q_\mathrm{eff}$ approaches. For comparison we also show (empty symbols) the luminosities from nuclear processes. Note that within the $Q_\mathrm{eff}$ method $\nu_{\mu,\,\tau}$, $\bar{\nu}_{\mu,\,\tau}$ can be produced only in thermal processes.
• Figure 4: Comparison of (anti)neutrino spectra from nuclear and thermal process at $t = 9.55$ h (left panels) and $t = 0$ (right panels). For $\nu_e$ and $\bar{\nu}_e$ we also compare the TQRPA and $Q_\textrm{eff}$ spectra from nuclear processes.
• Figure 5: Time evolution of the total $\nu_e$ (upper panels) and $\bar{\nu}_e$ (lower panels) luminosities. On each plot, the luminosities obtained with the normal (NH) and inverted (IH) hierarchy are compared with the original unoscillated luminosity (0). The left and right plots show the results obtained employing the TQRPA and $Q_\mathrm{eff}$ approaches.