We explore the role of neutrinos in a Quark Nova explosion. We study
production of neutrinos during this event, their propagation and their
interactions with the surrounding quark matter and neutron-rich envelope. We
address relevant physical issues such as the timescale for the initial core
collapse, the total energy emitted in neutrinos and their effect on the low
density matter surrounding the core. We find that it is feasible that the
neutrino burst can lead to significant mass ejection of the nuclear envelope.Comment: 20 pages, 5 figures (revised version- accepted for publication in
ApJ
Abstract. We present a new model for soft gamma-ray repeaters based on a quark star born with temperatures above the critical value (T c ) for the onset of the colour-flavor locked superconductivity. The quark star then quickly cools below T c , expelling a fraction of the surface magnetic field via the Meissner effect. We show that if a small fraction (≤10%) of the surface magnetic field (10 14 −10 15 G) is expelled, it quickly decays via magnetic reconnection and heats up the quark star surface to temperatures >10 9 K. Created (e + , e − ) pairs annihilate into gamma rays emitted in a giant burst (the first burst in our model), with a luminosity of ∼10 45 erg s −1 . Subsequent bursts result from the restructuring of the surface magnetic field following the formation and relaxation of a vortex lattice which confines the internal magnetic field. During this phase, energy is sporadically released as a consequence of magnetic reconnection events in the entangled surface magnetic field as it evolves into a smooth, more stable, configuration. The star eventually enters a quiescent phase in which energy is continuously supplied by vortex annihilation at the surface. As the star spins down, the outermost vortex lines will be pushed to the surface where they annihilate and release their confined magnetic field. We show that the corresponding luminosity is L v ∼ 10 36 erg s −1 for a typical soft gamma-ray repeater spinning with a period of 8 s and a surface magnetic field not exceeding 10 15 G. Our model can be applied to any situation where a T > T c quark star is generated. We discuss the connection between anomalous X-ray pulsars and soft gamma-ray repeaters in the context of our model.
In models with large extra dimensions all gauge singlet fields can in principle propagate in the extra dimensional space. We have investigated possible constraints on majoron models of neutrino masses in which the majorons propagate in extra dimensions. It is found that astrophysical constraints from supernovae are many orders of magnitude stronger than previous accelerator bounds. Our findings suggest that unnatural types of the "see-saw" mechanism for neutrino masses are unlikely to occur in nature, even in the presence of extra dimensions.
We consider the possibility that there exist sterile neutrinos which are
closely degenerate in mass with the active neutrinos and mixed with them. We
investigate the effects of this kind of active-sterile neutrino mixing on the
composition of supernova neutrino flux at the Earth. If an adiabatic
MSW-transition between active and sterile neutrinos takes place, it could
dramatically diminish the electron neutrino flux.Comment: 12 pages. Final version to be published in Phys. Lett.
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