We suggest that an extreme Kerr black hole with a mass \sim 10 ^ { 6 } M _ { \odot } , a dimensionless angular momentum A \sim 1 and a marginal stable orbital radius r _ { ms } \sim 3 r _ { s } \sim 10 ^ { 12 } M _ { 6 } ~ { } cm located in a normal galaxy , may produced a Gamma-ray Burst by capturing and disrupting a star .
During this period , a transient accretion disk is formed and a strong transient magnetic field \sim 2.4 \times 10 ^ { 9 } M _ { 6 } ^ { -1 / 2 } Gauss , lasting for r _ { ms } / c \sim 30 M _ { 6 } ~ { } s , may be produced in the inner boundary of the accretion disk .
A large amount of rotational energy of the black hole is extracted and released in the ultra relativistic jet with a bulk Lorentz factor \Gamma larger than 10 ^ { 3 } via Blandford-Znajek process .
The relativistic jet energy can be converted into \gamma -ray radiation via internal shock mechanism .
The gamma-ray burst ( GRB ) duration should be the same as that of the life time of the strong transient magnetic field .
The maximum number of sub-bursts is estimated to be r _ { ms } / h \sim ( 10 - 10 ^ { 2 } ) because the disk material is likely broken into pieces with the size about the thickness of the disk h at the cusp ( 2 r _ { s } \leq r \leq 3 r _ { s } ) .
The shortest rising time of the burst estimated from this model is \sim h / \Gamma c \sim 3 \times 10 ^ { -4 } \Gamma ^ { -1 } _ { 3 } ( h / r ) _ { -2 } M _ { 6 } s. The model gamma-ray burst density rate is also estimated .