Observing Supernova Neutrino Light Curves with Super-Kamiokande: Expected Event Number over 10 s

Abstract

Supernova neutrinos are crucially important to probe the final phases of massive star evolution. As is well known from observations of SN 1987A, neutrinos provide information on the physical conditions responsible for neutron star formation and on the supernova explosion mechanism. However, there is still no complete understanding of the long-term evolution of neutrino emission in supernova explosions, although there are a number of modern simulations of neutrino radiation hydrodynamics, which study neutrino emission at times less than one second after the bounce. In the present work we systematically calculate the number of neutrinos that can be observed in Super-Kamiokande over periods longer than ten seconds using the database of Nakazato et al. (2013) anticipating that neutrinos from a Galactic supernova can be detected for several tens of seconds. We find that for a supernova at a distance of 10 kpc, neutrinos remain observable for longer than 30 s for a low-mass neutron star (1.20M ⊙ gravitational mass) and even longer than 100 s for a high-mass neutron star (2.05M ⊙ ). These scenarios are much longer than the observations of SN 1987A and longer than the duration of existing numerical simulations. We propose a new analysis method based on the cumulative neutrino event distribution as a function of reverse time from the last observed event, as a useful probe of the neutron star mass. Our result demonstrates the importance of complete modeling of neutrino light curves in order to extract physical quantities essential for understanding supernova explosion mechanisms, such as the mass and radius of the resulting neutron star.

Characteristic time variability of gravitational-wave and neutrino signals from three-dimensional simulations of non-rotating and rapidly rotating stellar core collapse

“…Provided the expense of 3D-GR simulations with spectral neutrino transport, our simulation covers only ∼ 300 ms postbounce. Recently, it is pointed out that galactic supernova neutrinos 6 , depending on the neutron star mass, can be observed over 10 s after bounce (Suwa et al (2019), see also Nakazato & Suzuki (2020)). Possible phase transition 6 Pioneering theoretical work of this topics especially focusing on the black hole formation includes Keil & Janka (1995); Baumgarte et al (1996) from hadronic to quark matter in the PNS (Fischer et al 2018) can be imprinted in the GW signals (Zha et al 2020).…”

On the synthesis of heavy nuclei in protomagnetar outflows and implications for ultra-high energy cosmic rays

“…In order to explore the sensitivity of the results to uncertainties in Lν , ν and Rns evolution, we also use neutrino cooling curves from the recent calculations of Suwa et al (2019) [hereafter S19]. In Figure A1, we compare the P99 cooling curves with the low entropy Mns = 1.3 M (M1L) models of S19.…”

Supernova Model Discrimination with Hyper-Kamiokande

“…All data sets cover the time interval from 20msto520ms after the core bounce, which contains the shock stagnation and accretion phase. The earlier neutronization burst is much better understood and exhibits only minor variations between models (Kachelrieß et al 2005), while the later diffusive proto-neutron star cooling is expected to be quasistatic and physically much simpler than the hydrodynamic behavior of the shock wave (Suwa et al 2019;Li et al 2021). The accretion phase is thus expected to show the largest differences between models, making it most relevant for model discrimination.…”