Cococubed.com Pre-Supernova Neutrinos
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Presupernova neutrinos: directional sensitivity and prospects for progenitor identification (2020) In this article we explore the potential of current and future liquid scintillator neutrino detectors of $\mathcal O (10)$ kt mass to localize a pre-supernova neutrino signal in the sky. In the hours preceding the core collapse of a nearby star (at distance $D \lesssim$ 1 kpc), tens to hundreds of inverse beta decay events will be recorded, and their reconstructed topology in the detector can be used to estimate the direction to the star. Although the directionality of inverse beta decay is weak ($\sim$8% forward-backward asymmetry for currently available liquid scintillators), we find that for a fiducial signal of 200 events (which is realistic for Betelgeuse), a positional error of $\sim$60$^\circ$ can be achieved, resulting in the possibility to narrow the list of potential stellar candidates to less than ten, typically. For a configuration with improved forward-backward asymmetry ($\sim$40%, as expected for a lithium-loaded liquid scintillator), the angular sensitivity improves to $\sim$15$^\circ$, and -- when a distance upper limit is obtained from the overall event rate -- it is in principle possible to uniquely identify the progenitor star. Any localization information accompanying an early supernova alert will be useful to multi-messenger observations and to particle physics tests using collapsing stars. Number of events at a 17 kt liquid scintillator detector Cumulative number at a 17 kt liquid scintillator detector Nearby core collapse supernova candidates Mollweide projection of nearby core collapse supernova candidates. Geometry of inverse beta decay in liquid scintillator Angular uncertainty of localization Antares 4 hours before collapse Antares 1 hour before collapse Antares 2 min before collapse Neutrinos from beta processes in a presupernova: probing the isotopic evolution of a massive star (2017) In this article we present a new calculation of the neutrino flux received at Earth from a massive star in the $\sim$ 24 hours of evolution prior to its explosion as a supernova (presupernova). Using the stellar evolution code MESA, the neutrino emissivity in each flavor is calculated at many radial zones and time steps. In addition to thermal processes, neutrino production via beta processes is modeled in detail, using a network of 204 isotopes. We find that the total produced $\nu_e$ flux has a high energy spectrum tail, at E $\gtrsim$ 3 - 4 MeV, which is mostly due to decay and electron capture on isotopes with A = 50 - 60. In a tentative window of observability of E $\gtrsim$ 0.5 MeV and t < 2 hours pre-collapse, the contribution of beta processes to the $\nu_e$ flux is at the level of $\sim$ 90% . For a star at D=1 kpc distance, a 17 kt liquid scintillator detector would typically observe several tens of events from a presupernova, of which up to $\sim$ 30% due to beta processes. These processes dominate the signal at a liquid argon detector, thus greatly enhancing its sensitivity to a presupernova. neutrino luminosity evolutions neutrino spectra $\nu$ luminosity evolution at different energies fluxes at earth for 15 M$_{\odot}$ fluxes at earth for 30 M$_{\odot}$