Development of an early warning method incorporating pre-supernova neutrino light curves

TL;DR

This work addresses the challenge of providing an early warning for core-collapse supernovae by exploiting the time evolution of pre-SN neutrino signals. It introduces a rate+time log-likelihood alarm that profiles over the core-collapse time $t^*$ and integrates multiple pre-SN light-curve models to assess robustness. Applying the method to simulated KamLAND, SK-Gd, and their combination, the authors show substantial improvements in alert lead times while preserving the same false-alarm rate compared to conventional rate-only approaches. The approach enhances sensitivity to more distant sources and offers practical benefits for early notification systems in astronomy and multi-messenger observations.

Abstract

Massive stars ($M>8\mathrm{M_\odot}$) emit neutrinos known as pre-supernova (pre-SN) neutrinos through thermal and nuclear interactions for cooling the stellar core during the final stage of stellar evolution. Real-time monitoring of their pre-SN neutrino interaction rate offers a crucial opportunity to issue an early warning to a core-collapse supernova. Some neutrino detectors, including KamLAND and Super-Kamiokande already operate pre-SN alarm systems based on a statistically significant excess of the observed event rate over the expected background. To improve alarm sensitivity, we propose an alarm method which incorporates the time evolution of the observed pre-SN neutrino event rate. The method uses a log likelihood ratio test that references multiple theoretical stellar-evolution models and treats the core collapse time as a nuisance parameter to be profiled over. The performance of the proposed method was evaluated using simulated data for the KamLAND, Super-Kamiokande with dissolved Gadolinium (SK-Gd) and their combined analysis. The results demonstrate a significant improvement in the warning time compared to the conventional rate-only method, while maintaining the same false alarm rate.

Figures (5)

• Figure 1: Electron antineutrino luminosity and their average energy are shown as a function of time before core collapse (horizontal axis). Oxygen- and Silicon-shell burning produce peaks around $-10^5$ s and $-10^4$ s before core collapse, respectively.
• Figure 2: Time evolution of pre-SN event rate in (a) KamLAND and (b) Super-Kamiokande for the stars at $150\,\mathrm{pc}$. The mass orderings are assumed to be normal. The pre-SN neutrino light curve models are summarized in Table \ref{['table:ReferenceModel']}.
• Figure 3: Time evolution of expected FAR in KamLAND. (a) presents the alarm sensitivity of Odrzywolek model. (b) presents the alarm sensitivity of Patton model. The horizontal dashed light-blue line represents FAR of $1\,\mathrm{/century}$.
• Figure 4: Time evolution of expected FAR in SK. (a) presents the alarm sensitivity of Odrzywolek model. (b) presents the alarm sensitivity of Patton model. The horizontal dashed light-blue line represents FAR of $1\,\mathrm{/century}$.
• Figure 5: Time evolution of expected FAR in combined alarm case. (a) presents the alarm sensitivity of Odrzywolek model. (b) presents the alarm sensitivity of Patton model. The horizontal dashed light-blue line represents FAR of $1\,\mathrm{/century}$.