Detection of Neutrinos from Supernovae in Nearby Galaxies

Abstract

While existing detectors would see a burst of many neutrinos from a Milky Way supernova, the supernova rate is only a few per century. As an alternative, we propose the detection of ∼ 1 neutrino per supernova from galaxies within 10 Mpc, in which there were at least 9 core-collapse supernovae since 2002. With a future 1-Mton scale detector, this could be a faster method for measuring the supernova neutrino spectrum, which is essential for calibrating numerical models and predicting the redshifted diffuse spectrum from distant supernovae. It would also allow a > ∼ 10 4 times more precise trigger time than optical data alone for high-energy neutrinos and gravitational waves. One of the unsolved problems of astrophysics is how core-collapse supernovae explode. Nuclear fusion reactions in the core of a massive star produce progressively heavier elements until a Chandrasekhar mass of iron is formed, and electron degeneracy pressure cannot support the core under the weight of the stellar envelope. The core collapses until it reaches nuclear densities and neutrino emission begins; then an outgoing bounce shock should form, unbinding the envelope and producing the optical supernova. While successful in nature, in most numerical supernova models, the shock stalls, so that the fate of the entire star is to produce a black hole (after substantial neutrino emission), but no optical supernova.Since the gravitational energy release transferred to neutrinos, about 3× 10 53 erg, is ∼ 100 times greater than the required kinetic energy for the explosion, it is thought that neutrino emission and interactions are a key diagnostic or ingredient of success. However, not enough is directly known about the total energies and temperatures of the neutrino flavors. The ≃ 20 events from SN 1987A were only crudely consistent with expectations forν e , and gave very little information on the other flavors [1]. It is thus essential to collect more supernova neutrino events. A Milky Way supernova would allow detailed measurements, but the supernova rate is only a few per century. If Super-Kamiokande were loaded with GdCl 3 [2], the diffuse supernova neutrino background (DSNB) [3,4,5] could be cleanly detected, probing the supernova neutrino spectrum, but convolved with the rapidly evolving star formation rate [6] up to redshift z ≃ 1.We propose an intermediate regime, in which the number of events per supernova is ∼ 1, instead of ≫ 1 (Milky Way) or ≪ 1 (DSNB), motivated by the serious consideration of 1-Mton scale water-Čerenkov detectors in Japan ), the United States (UNO [8]), and Europe (MEMPHYS [9]). These detectors, which may operate for decades, are intended for proton decay and long-baseline accelerator neutrino oscillation studies,

Sources of Gravitational Waves: Theory and Observations

“…Supernovae were the prime targets for the first GW detectors and they are still among the most important sources. The Galactic supernova rate is uncertain and is thought to be between 0.01-0.1 per year, but the rate within about 5 Mpc could be one per few years [428].…”

The diffuse supernova neutrino flux, supernova rate and SN1987A

“…[62] using method (2), with the modified Salpeter B initial mass function (Table 2 in [62]) and the interval of progenitor masses as in Eq. (7).…”

Gravitational lensing of supernova neutrinos

“…For a supernova at a distance of 1 Mpc the magnification would be again enormous, µ ≈ 10 12 . An unlensed supernova at this distance for which one detected neutrino event would be expected [74] would result in some 10 12 events if perfectly aligned with αCen and Earth. It is thus conceivable that lensing could allow for the detection of significant numbers of neutrinos from more distant supernovae.…”