Jet precession driven by neutrino-cooled disk for gamma-ray bursts

¹ Department of Astronomy, Nanjing University, Nanjing, Jiangsu 210093, PR China e-mail: tongliu@nju.edu.cn
² Department of Physics, Guangxi University, Nanning, Guangxi, 530004, PR China
³ Department of Physics and Institute of Theoretical Physics and Astrophysics, Xiamen University, Xiamen, Fujian 361005, PR China
⁴ National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, Kunming, Yunnan, 650011, PR China
⁵ Key Laboratory for the Structure and Evolution of Celestial Bodies, Chinese Academy of Sciences, Kunming, Yunnan, 650011, PR China

Received: January 1900
Accepted: 12 March 2010

Abstract

Aims. A model of jet precession driven by a neutrino-cooled disk around a spinning black hole is presented to explain the temporal structure and spectral evolution of gamma-ray bursts (GRBs).

Methods. The differential rotation of the outer part of a neutrino-dominated accretion disk may result in precession of the inner part of the disk and the central black hole, hence driving a precessed jet via neutrino annihilation around the inner part of the disk.

Results. Both analytic and numeric results for our model are presented. Our calculations show that a black-hole, accretion-disk system with the black hole mass M 3.66 , accretion rate 0.54 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 = 10⁵¹ erg s^-1, corresponding to the scenario for long GRBs. A precessed jet with P = 0.1 s and L = 10⁵⁰ erg s^-1 may be powered by a system with M 5.59 , 0.74 , a = 0.1, and α = 0.01, and is possibly responsible for the short GRBs. Both the temporal and spectral evolution in GRB pulse may be explained with our model.

Conclusions. GRB central engines most likely power a precessed jet driven by a neutrino-cooled disk. 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 stem from a viewing effect of the jet precession.