Speaker
Description
Failed supernovae are stellar core-collapse events in which the explosion does not succeed, and the core collapses directly into a black hole. In such a scenario, neutrinos are emitted and suddenly disappear once a black hole forms, making their observed time profile a direct indicator of black hole formation.
In 2024, a candidate failed supernova, M31-2014-DS1, was reported in the Andromeda galaxy at a distance of about 770 kpc. Optical observations showed a gradual fading of the progenitor, while near-infrared data indicated sustained emission consistent with dust heating in the surrounding environment. These multi-wavelength signatures suggest that the stellar core may have collapsed without launching a successful explosion. This object offers a rare opportunity to search for neutrinos from a supernova beyond the Milky Way, making it one of the most promising candidates since SN 1987A. For a failed supernova occurring at a distance of order 1 Mpc, the expected number of detected neutrino events in Super-Kamiokande (SK) decreases to approximately O(1). Rather than a supernova within our Galaxy, which would yield thousands of neutrino events and therefore provide high statistics, the signal from such a distant supernova would consist of only a few neutrino events clustered within a short time interval. Based on the estimated time of black hole formation inferred from optical and infrared observations, we define a search window for candidate neutrino events and apply a cluster search utilizing both timing and energy information.
In this poster, we present the results of a neutrino search for M31-2014-DS1 using data from the SK.
Furthermore, we evaluate the future sensitivity to failed supernova observations in the SK-Gd experiment. The addition of gadolinium to the detector enables efficient neutron tagging via delayed gamma rays from neutron capture, substantially reducing backgrounds. This improvement allows the analysis threshold to be lowered and enhances the discovery potential for extragalactic events.
As a future perspective, we also briefly discuss the sensitivity of Hyper-Kamiokande (HK), the next-generation detector of SK, whose larger effective volume further enhances the reach of such searches. Overall, these results demonstrate that the prospects for observing supernova neutrinos, including those from failed supernovae, are significantly improved in upcoming SK-Gd and HK experiments.