A possible energy mechanism for cosmological γ-ray bursts |
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| Authors: | K S Cheng Y Lu |
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| Institution: | Department of Physics, University of Hong Kong, Pokfulam Road, Hong Kong, China;Beijing Astronomical Observatory, Chinese Academy of Sciences, Beijing 100080, China;Department of Physics, Huang Zhong Normal University, 430079, China |
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| Abstract: | We suggest that an extreme Kerr black hole with a mass ～106 M⊙, a dimensionless angular momentum  and a marginally stable orbital radius  located in a normal galaxy may produce a γ -ray burst (GRB) by capturing and disrupting a star. During the capture period, a transient accretion disc is formed and a strong transient magnetic field ～  lasting for  may be produced at the inner boundary of the accretion disc. A large amount of rotational energy of the black hole is extracted and released in an ultrarelativistic jet with a bulk Lorentz factor Γ larger than 103 via the Blandford–Znajek process. The relativistic jet energy can be converted into γ -radiation via an internal shock mechanism. The GRB duration should be the same as the lifetime of the strong transient magnetic field. The maximum number of sub-bursts is estimated to be  because the disc material is likely to break into pieces with a size about the thickness of the disc h at the cusp  The shortest risetime of the burst estimated from this model is ～  The model GRB density rate is also estimated. |
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| Keywords: | accretion accretion discs black hole physics radiation mechanisms: non-thermal galaxies: general gamma-rays: bursts gamma-rays: theory |
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