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arXiv 1301.1102astro-ph.HEhep-ph
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超吸积流中的全球中微子加热

Global Neutrino Heating in Hyperaccretion Flows

Shu Luo, Feng Yuan

摘要:

吸积率为\dot{M} = 0.01 - 10 M_{\sun} s^{-1}的中微子主导吸积流是伽马射线暴(GRB)中心引擎的可能候选者。这种超吸积盘在径向上对中微子来说是光学薄的,因此在一个半径处产生的中微子可以在盘中传播很长的距离。因此,这些中微子可以以一定的概率被另一半径处的盘物质吸收,并加热那里的盘。这种“全球中微子加热”的影响在以前的工作中被忽略了,这是本文的重点。我们发现,在“点火”半径r_{ign}附近,中微子的整体加热率可以与局部粘性加热率相当甚至更大,因此中微子的整体加热率是一个重要的过程。如果考虑“全球中微子加热”,则可能有两种结果:i)盘的温度略有升高,“点火”半径r_{ign}向大半径方向略有移动,两者都导致总中微子通量的增加; ii)更有趣的是,刚好超过r_{ign}的ADAF的温度可以升高到维里温度以上,因此吸积将被抑制。在这种情况下,预计黑洞的活动将在活动和非活动阶段之间振荡。活动阶段的时间尺度估计为\sim 1秒。如果不活跃相的时间尺度与这个值相当或小于这个值,那么这种间歇性的活动就可以解释伽玛暴的慢变成分。未来需要对包含“全球中微子加热”的NDAF进行自洽的全球计算,以更精确地评估这种效应。

英文摘要:

The neutrino-dominated accretion flow (NDAF) with accretion rates \dot{M} = 0.01 - 10 M_{\sun} s^{-1} is a plausible candidate for the central engine of gamma-ray bursts (GRBs). This hyperaccretion disk is optically thin to neutrinos in the radial direction, therefore the neutrinos produced at one radius can travel for a long distance in the disk. Those neutrinos can thus be absorbed with certain probability by the disk matter at the other radius and heat the disk there. The effect of this "global neutrino heating" has been ignored in previous works and is the focus of this paper. We find that around the "ignition" radius r_{ign}, the global neutrino heating rate could be comparable to or even larger than the local viscous heating rate thus must be an important process. Two possible consequences are in order if the "global neutrino heating" is taken into account: i) the temperature of the disk is slightly raised and the "ignition" radius r_{ign} slightly shifts to a larger radius, both lead to the increasing of the total neutrino flux; ii) what is more interesting is that, the temperature of the ADAF just beyond r_{ign} may be raised above the virial temperature thus the accretion will be suppressed. In this case, the activity of the black hole is expected to oscillate between an active and inactive phases. The timescale of the active phases is estimated to be \sim 1 second. If the timescale of the inactive phase is comparable to or less than this value, this intermittent activity may explain the slow variability component of the GRBs. Self-consistent global calculations of NDAFs with the "global neutrino heating" included are required in the future to more precisely evaluate this effect.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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