A hyperaccretion disk formed around a stellar-mass black hole is a plausible model for the central engine that powers gamma-ray bursts (GRBs). If the central black hole rotates and a poloidal magnetic field threads its horizon, a powerful relativistic jet may be driven by a process resembling the Blandford-Znajek (BZ) mechanism. We estimate the luminosity of such a jet as a function of mass accretion rate and other accretion parameters assuming that the poloidal magnetic field strength is comparable to the inner accretion disk pressure. We show that the jet efficiency attains its maximal value when the accretion flow is cooled via optically thin neutrino emission. The jet luminosity is much larger than the energy deposition through neutrino-antineutrino annihilation () provided that the black hole is spinning rapidly enough. When the accretion rate onto a rapidly spinning black hole is larger than 0.003-0.01 M ☉ s–1, the disk becomes optically thin to neutrinos, its pressure increases and the jet luminosity is sufficient to drive a GRB. The transition of the accretion rate above and below this limiting value may cause the large variability observed in GRB.
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机译：在恒星质量黑洞周围形成的超积圆盘是为中央引擎提供动力的合理模型，该引擎为伽马射线爆发（GRB）提供动力。如果中心黑洞旋转，并且极地磁场沿其视界穿线，则类似于Blandford-Znajek（BZ）机制的过程可能会驱动强大的相对论射流。假定极向磁场强度与内部吸积盘压力相当，我们估计这种射流的发光度是质量吸积率和其他吸积参数的函数。我们显示，当吸积流通过光学上薄的中微子发射冷却时，射流效率达到最大值。如果黑洞足够快地旋转，则射流的发光度比通过中微子-抗中微子an灭产生的能量大得多。当快速旋转的黑洞上的吸积率大于0.003-0.01 M s-1时，圆盘在光学上变薄为中微子，其压力增加，射流的光度足以驱动GRB。吸积率高于或低于此极限值的转变可能会导致GRB中观察到很大的变化。
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