短暴对应中微子主导吸积盘的盘质量

The mass of the neutrino-dominated accretion disks in short gamma-ray bursts

短暴最有可能起源于双致密星并合.因为这种情形产生的吸积盘较小,持续时间可以和短暴的持续时标相当.模拟结果显示,双星并合产生的吸积盘质量远低于双星质量的总和.本文利用现有的观测数据,估算了恒星级黑洞周围中微子主导吸积盘的质量.结果显示,短暴吸积盘质量的估算主要取决于它的喷流能量和张角及黑洞的质量和自旋.一些短暴要求具有很大质量的吸积盘,这个数值已经达到甚至超过了模拟的最大值.我们认为,可能存在其他的电磁动力学过程或者其他的机制可以提高中微子辐射效率,从而提供短暴爆发所需要的能量.

The coalesence of compact binary systems might be the plausible candidate to power short Gamma-Ray Bursts（GRBs）, since in this scenario a low mass disk can be formed, and the lifetime of the disk is comparable to the duration of the short GRBs. After merger, a neutrino-dominated accretion flow（NDAF） surrounding a stellar-mass black hole（BH） will be formed and neutrino-antineutrino annihilation above the disk may power short GRBs. The results of the simulation show that the disk mass of the NDAF has a limit after merger events. So the question is： can annihilations of neutrinos from NDAFs owning such disk masses power all the observed short GRBs？ Using the current short GRB observational data and fireball model, we estimate the disk mass of the NDAF. The neutrino annihilation luminosity as a function of BH spin and accretion rate is fitted from the global solutions of NDAFs. The results show that the estimation of the disk mass mainly depends on its output energy, jet opening angle, and central BH characteristic of GRBs. And some short GRBs require massive disks, which approach or exceed the limits in simulations. If the precise value of jet opening angle is considered, the real requirements of the disk masses will be much larger than the present results, since we use only the lower limit of them in the calculation. These results reflect that the neutrino annihilation process is deficient to power short GRBs. We suggest that there may exit other magnetohydrodynamic processes or some mechanisms to increase the efficiency of the neutrino emission, and then provide energy to power short GRBs.