Abstract

In the binary-driven hypernova model of long gamma-ray bursts, a carbon–oxygen star explodes as a supernova in the presence of a neutron star binary companion in close orbit. Hypercritical (i.e., highly super-Eddington) accretion of the ejecta matter onto the neutron star sets in, making it reach the critical mass with consequent formation of a Kerr black hole. We have recently shown that, during the accretion process onto the neutron star, fast neutrino flavor oscillations occur. Numerical simulations of the above system show that a part of the ejecta stays bound to the newborn Kerr black hole, leading to a new process of hypercritical accretion. We address herein, also for this phase of the binary-driven hypernova, the occurrence of neutrino flavor oscillations given the extreme conditions of high density (up to 1012 g cm−3) and temperatures (up to tens of MeV) inside this disk. We estimate the behavior of the electronic and non-electronic neutrino content within the two-flavor formalism (νeνx) under the action of neutrino collective effects by neutrino self-interactions. We find that in the case of inverted mass hierarchy, neutrino oscillations inside the disk have frequencies between ∼(105–109) s−1, leading the disk to achieve flavor equipartition. This implies that the energy deposition rate by neutrino annihilation (ν+ν¯→e−+e+) in the vicinity of the Kerr black hole is smaller than previous estimates in the literature not accounting for flavor oscillations inside the disk. The exact value of the reduction factor depends on the νe and νx optical depths but it can be as high as ∼5. The results of this work are a first step toward the analysis of neutrino oscillations in a novel astrophysical context, and as such, deserve further attention.

Highlights

  • Neutrino flavor oscillations are an experimental fact [1], and in recent years, their study based only on Mikheyev–Smirnov–Wolfenstein (MSW) effects [2,3] has been transformed by the insight that refractive effects of neutrinos on themselves due to the neutrino self-interaction potential are essential

  • For this phase of the binary-driven hypernova, the occurrence of neutrino flavor oscillations given the extreme conditions of high density and temperatures inside this disk

  • This article aims to explore the problem of neutrino flavor oscillations in the case of long gamma-ray bursts (GRBs), in particular in the context of the binary-driven hypernova (BdHN) scenario

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Summary

Introduction

Neutrino flavor oscillations are an experimental fact [1], and in recent years, their study based only on Mikheyev–Smirnov–Wolfenstein (MSW) effects [2,3] has been transformed by the insight that refractive effects of neutrinos on themselves due to the neutrino self-interaction potential are essential Their behavior in a vacuum, in matter or by neutrino self-interactions has been studied in the context of early universe evolution [4,5,6,7,8,9,10,11,12,13,14,15], solar and atmospheric neutrino anomalies [16,17,18,19,20,21,22,23,24] and core-collapse supernovae (SN) ([25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51] and references therein).

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