标题： 塌缩星吸积模式——伽马射线暴产生的前景 显示英文标题

标题： Accretion modes in collapsars - prospects for GRB production

摘要： 我们研究了低角动量吸积流落入由大质量恒星核心坍缩后形成的黑洞的情况。 特别是，我们考虑了气体以准球状方式落入恒星级黑洞的状态，在超临界状态下，吸积率在每秒0.001到0.5个太阳质量之间，并且中微子主导冷却过程。 先前的研究假设，为了让黑洞切换到明亮状态，条件l >> r_g c（其中l是下落气体的比轨道角动量，r_g是史瓦西半径）需要满足。 我们认为，在超吸积、围绕黑洞的恒星级盘中的流动很可能在角动量刚刚高于盘形成阈值时过渡到高度辐射状态，即l ~ 2 r_g c。在l介于r_g c和2 r_g c之间的范围内，会形成一个矮小的盘，在这里由于广义相对论效应，气体螺旋式地快速落入黑洞，而无需水平粘性应力的帮助。 对于旋转速率较高的情况（l大于2 r_g c），亮度由围绕黑洞的大而热的赤道气泡提供。 最高中微子亮度出现在l ~ 2 r_g c时，这个角动量值也产生最具能量的中微子，因此也是最高的能量沉积率。 鉴于本工作中探索的l范围，我们认为，只要l大于2 r_g c，低角动量核可能实际上更适合在超新星和伽马射线暴的核心坍缩后产生中微子驱动的爆炸。 显示英文摘要

摘要： We explore low angular momentum accretion flows onto black holes formed after the collapse of massive stellar cores. In particular, we consider the state of the gas falling quasi-spherically onto stellar-mass black holes in the hypercritical regime, where the accretion rates are in the range 0.001 - 0.5 solar masses per second and neutrinos dominate the cooling. Previous studies have assumed that in order to have a black hole switch to a luminous state, the condition l >> r_g c, where l is the specific orbital angular momentum of the infalling gas and r_g is the Schwarszchild radius, needs to be fulfilled. We argue that flows in hyperaccreting, stellar mass disks around black holes are likely to transition to a highly radiative state when their angular momentum is just above the threshold for disk formation, l ~ 2 r_g c. In a range where l lies between r_g c and 2 r_g c, a dwarf disk forms in which gas spirals rapidly into the black hole due to general relativistic effects, without any help from horizontal viscous stresses. For high rotation rates with l greater than 2 r_g c, the luminosity is supplied by large, hot equatorial bubbles around the black hole. The highest neutrino luminosities are obtained for l ~ 2 r_g c, and this value of angular momentum also produces the most energetic neutrinos, and thus also the highest energy deposition rates. Given the range of l explored in this work, we argue that, as long as l is greater than 2 r_g c, low angular momentum cores may in fact be better suited for producing neutrino--driven explosions following core collapse in supernovae and gamma ray bursts.