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arXiv 1701.02017astro-ph.HE
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合并残余物上方的中微子对湮灭:长寿命大质量中子星的意义

Neutrino pair annihilation above merger remnants: implications of a long-lived massive neutron star

Albino Perego, Hannah Yasin, Almudena Arcones

摘要:

双中子星合并是短伽马射线暴(GRB)的可能祖先,但是,仍然缺乏对它们的中心引擎的详细解释。中微子对的湮灭被认为是可能的动力机制之一。我们目前的能量和动量沉积的中微子对湮灭以上合并残留物操作的计算。从一个详细的,三维模拟的后果的二元中子星合并的结果,我们计算的沉积率在一个时间尺度上相当于磁盘的寿命($t \approx 0.4$),假设一个长寿的大质量中子星(MNS)。我们使用光谱泄漏方案模拟中微子发射,并使用射线追踪算法计算中微子湮灭率。我们发现,MNS的存在下增加了能量沉积率的一个因素$\sim 2$,主要是由于湮灭的辐射来自MNS与辐射来自磁盘。我们计算了相对论效应的影响,发现尽管它们可以显著改变局部速率强度,但体积积分结果仅略有下降。外推至1秒的累积沉积能量为$\approx 2.2 \times 10^{49} \, {\rm erg}$。与推断的短伽玛射线暴能量学的比较表明,在大多数情况下,这种能量是不够大的,即使假设小喷流张开角和长寿命的MNS。要解释大多数观测到的短伽马射线暴,需要更强的中微子光度(大约大5-10倍)。我们的结论是,这是不太可能的中微子对湮灭可以单独解释短伽玛暴的中央引擎。

英文摘要:

Binary neutron star mergers are plausible progenitor candidates for short gamma-ray bursts (GRBs); however, a detailed explanation of their central engine is still lacking. The annihilation of neutrino pairs has been proposed as one of the possible powering mechanisms. We present calculations of the energy and momentum deposition operated by neutrino pair annihilation above merger remnants. Starting from the results of a detailed, three-dimensional simulation of the aftermath of a binary neutron star merger, we compute the deposition rates over a time scale comparable to the life time of the disk ($t \approx 0.4$ s), assuming a long-lived massive neutron star (MNS). We model neutrino emission using a spectral leakage scheme and compute the neutrino annihilation rates using a ray-tracing algorithm. We find that the presence of the MNS increases the energy deposition rate by a factor $\sim 2$, mainly due to the annihilation of radiation coming from the MNS with radiation coming from the disk. We compute the impact of relativistic effects and discover that, despite they can significantly change the local rate intensity, the volume-integrated results are only marginally decreased. The cumulative deposited energy, extrapolated to 1 sec, is $\approx 2.2 \times 10^{49} \, {\rm erg}$. A comparison with the inferred short GRB energetics reveals that in most cases this energy is not large enough, even assuming small jet opening angles and a long-lived MNS. Significantly more intense neutrino luminosities (a factor ~5-10 larger) are required to explain most of the observed short GRB. We conclude that it is unlikely that neutrino pair annihilation can explain the central engine of short GRBs alone.

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