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

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, an alarm method which incorporates the time evolution of the observed pre-SN neutrino event rate was proposed in A. Sheshukov et al. (2021). We evaluate the performance of the light-curve likelihood approach under realistic KamLAND and SK operating conditions, including realistic background rates, global false-alarm-rate calibration, and the combined alarm. The results demonstrate a significant improvement in the alarm time and distance compared to the conventional rate-only method, while maintaining the same false alarm rate.