arXivDaily arXiv每日学术速递 周一至周五更新
arXiv周末暂无论文更新,休息一下吧,周末愉快~~
arXiv 1604.02455astro-ph.HEgr-qc
收藏

中子星合并:短伽马射线暴的喷气发动机

Binary neutron star mergers: a jet engine for short gamma-ray bursts

Milton Ruiz, Ryan N. Lang, Vasileios Paschalidis, Stuart L. Shapiro

摘要:

我们进行磁流体动力学模拟在全广义相对论(GRMHD)的准圆形,等质量,双中子星进行合并。最初的恒星是无旋的,$n=1$多面体,并被磁化。我们探讨了两种类型的磁场几何形状:一种是每个恒星都被赋予了一个从内部延伸到外部的偶极磁场,就像脉冲星一样,另一种是偶极场最初被限制在内部。在这两种情况下,所采用的磁场最初在动态上是不重要的。合并的结果是一个超大质量的中子星,它经历了延迟坍缩,变成一个黑洞(自旋参数$a/M_{\rm BH} \sim 0.74$),沉浸在磁化的吸积盘中。合并后约$4000M \sim 60(M_{\rm NS}/1.625M_\odot)$ ms,黑洞两极上方的区域被强烈磁化,并产生一个平行的、温和的相对论性外流--一个初始喷流。吸积盘的寿命可能等于喷流的寿命,它是$Δt \sim 0.1 (M_{\rm NS}/1.625M_\odot)$ s。相反,黑洞-中子星合并,我们发现,即使初始的磁场被限制在内部的恒星,初期的射流发射。

英文摘要:

We perform magnetohydrodynamic simulations in full general relativity (GRMHD) of quasi-circular, equal-mass, binary neutron stars that undergo merger. The initial stars are irrotational, $n=1$ polytropes and are magnetized. We explore two types of magnetic-field geometries: one where each star is endowed with a dipole magnetic field extending from the interior into the exterior, as in a pulsar, and the other where the dipole field is initially confined to the interior. In both cases the adopted magnetic fields are initially dynamically unimportant. The merger outcome is a hypermassive neutron star that undergoes delayed collapse to a black hole (spin parameter $a/M_{\rm BH} \sim 0.74$) immersed in a magnetized accretion disk. About $4000M \sim 60(M_{\rm NS}/1.625M_\odot)$ ms following merger, the region above the black hole poles becomes strongly magnetized, and a collimated, mildly relativistic outflow --- an incipient jet --- is launched. The lifetime of the accretion disk, which likely equals the lifetime of the jet, is $Δt \sim 0.1 (M_{\rm NS}/1.625M_\odot)$ s. In contrast to black hole--neutron star mergers, we find that incipient jets are launched even when the initial magnetic field is confined to the interior of the stars.

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。

↑