Strongest gravitational waves from neutrino oscillations at supernova core bounce

Abstract

Resonant active-to-active (νa → νa), as well as active-to-sterile (νa → νs) neutrino (ν) oscillations can take place during the core bounce of a supernova collapse. Besides, over this phase, weak magnetism increases the antineutrino (¯ν) mean free path, and thus its luminosity. Because the oscillation feeds massenergy into the target ν species, the large mass-squared difference between the species (νa → νs) implies a huge amount of energy to be given off as gravitational waves (LGW ∼ 1049 erg s−1), due to anisotropic but coherent ν flow over the oscillation length. This asymmetric ν-flux is driven by both the spin–magnetic and the universal spin–rotation coupling. The novel contribution of this paper stems from (1) the new computation of the anisotropy parameter α ∼ 0.1–0.01, and (2) the use of the tight constraints from neutrino experiments as SNO and KamLAND, and the cosmic probe WMAP, to compute the gravitational-wave emission during neutrino oscillations in supernovae core collapse and bounce. We show that the mass of the sterile neutrino νs that can be resonantly produced during the flavor conversions makes it a good candidate for dark matter as suggested by Fuller et al., Phys. Rev. D 68, 103002 (2003). The new spacetime strain thus estimated is still several orders of magnitude larger than those from ν diffusion (convection and cooling) or quadrupole moments of neutron star matter. This new feature turns these bursts into the more promising supernova gravitational-wave signals that may be detected by observatories as LIGO, VIRGO, etc., for distances far out to the VIRGO cluster of galaxies.