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Jet Precession Driven by Neutrino-Cooled Disc for Gamma-Ray Bursts

A model of jet precession driven by a neutrino-cooled disc around a spinning black hole is present in order to explain the temporal structure and spectral evolution of gamma-ray bursts (GRBs). The differential rotation of the outer part of a neutrino dominated accretion disc may result in precession of the inner part of the disc and the central black hole, hence drives a precessed jet via neutrino annihilation around the inner part of the disc. Both analytic and numeric results for our model are present. Our calculations show that a black hole-accretion disk system with black hole mass $M \simeq 3.66 M_\odot$, accretion rate $\dot{M} \simeq 0.54 M_\odot \rm s^{-1}$, spin parameter $a=0.9$ and viscosity parameter $α=0.01$ may drive a precessed jet with period P=1 s and luminosity $L=10^{51}$ erg s$^{-1}$, corresponding to the scenario for long GRBs. A precessed jet with $P=0.1$s and $L=10^{50}$ erg s$^{-1}$ may be powered by a system with $M \simeq 5.59 M_\odot$, $\dot{M} \simeq 0.74 M_\odot \rm s^{-1}$, $a=0.1$, and $α=0.01$, possibly being responsible for the short GRBs. Both the temporal and spectral evolution in GRB pulse may explained with our model. GRB central engines likely power a precessed jet driven by a neutrino-cooled disc. The global GRB lightcurves thus could be modulated by the jet precession during the accretion timescale of the GRB central engine. Both the temporal and spectral evolution in GRB pulse may be due to an viewing effect due to the jet precession.