吸积的恒星级黑洞周围的中微子对湮灭

astro-ph/0608543 [abs, ps, pdf, other] :

Title: Neutrino pair annihilation near accreting, stellar-mass black holes
Authors: R. Birkl (1), M.-A. Aloy (1,2), H.-Th. Janka (1), E. Mueller (1) ((1) MPI for Astrophysics, Garching, Germany, (2) Depto. Astronomia y Astrofisica UVEG, Spain)
Comments: 19 pages, 8 figures, submitted to A&A

We investigate the energy-momentum deposition due to neutrino-antineutrino annihilation in the vicinity of axisymmetric, accreting black holes (BHs) by numerically ray-tracing neutrino trajectories in a Kerr space-time. Hyperaccreting stellar-mass BHs are widely considered as energy sources that can drive ultrarelativistic outflows with the potential to produce gamma-ray bursts. In contrast to earlier works, we provide an extensive and detailed parameter study of the influence of general relativistic (GR) effects and of different neutrinosphere geometries. These include idealized thin disks, tori, and spheres, or are constructed as non-selfgravitating equilibrium matter distributions for varied BH rotation. Considering isothermal neutrinospheres with the same temperature and surface area, we confirm previous results that compared to Newtonian calculations, GR effects increase the annihilation rate measured by an observer at infinity by a factor of 2 when the neutrinosphere is a disk. However, in case of a torus and a sphere the influence of GR effects is globally only ~25%, although locally it can be significantly larger. Independent of whether GR effects are included, disks yield the highest energy deposition rates, followed by tori and, with the lowest rates, spheres. For disks and tori, increasing the angular momentum of the BH from 0 to 1 enhances the energy deposition rate measured by an observer at infinity by roughly a factor of 2 due to the shrinking inner radius of the neutrinosphere. (abridged)

译文：
通过在Kerr时空中的中微子轨迹的数值光线追踪计算，我们研究了中微子对湮灭在一个轴对称的，吸积的黑洞周围的能量－动量沉积。超吸积的恒星级黑洞被广泛认为是驱动伽玛暴所需的极端相对论喷流的能源。相对于早期的模型，我们更加广泛地和详细地参数化地研究了广义相对论效应以及中微子球几何的影响。包括理想化的薄盘，环，球，以及构造成为非自引力平衡物质分布对于各种黑洞旋转。考虑具有同样温度和表面积的等温中微子球，与之前的牛顿框架的计算对比发现，当中微子球是盘使，GR效应使得无穷远处观测者测量的湮灭效率提高了2倍。然而，如果是环和球，整体的GR影响只有25%，尽管局部很大。不管有没有考虑GR效应，盘总是沉积能量效率最高的，其次是环，最少的是球。对于盘和环，使BH的角动量从0到1，将导致无穷远观测者测定的能量沉积率提到2倍，这是由于中微子球内半径收缩引起的。

Comment:
超吸积中的中微子过程也是解释伽玛暴的另一主流模型，值得关注和学习。难得的是，本文还讨论了广义相对论效应，以及ray tracing的技巧。