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arXiv 0907.0561astro-ph.HE
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用广义相对论MHD模拟理解GRB-SN联系

Understanding of GRB-SN Connection by General Relativistic MHD Simulations

S. Nagataki

摘要:

我已经开发了两个数字代码来研究的动力学的missars。一个是二维MHD代码,使用牛顿(ZEUS-2D)代码,其中考虑到现实的状态方程,中微子冷却和加热过程。另一个是二维广义相对论磁流体动力学(GRMHD)程序。我已经用这些代码和现实的祖先模型进行了数值模拟。在牛顿程序中,发现中微子加热过程不足以在本研究中发射喷流。研究还发现,射流主要是由环形场发射的,环形场被卷绕效应放大。然而,由于总能量相对于射流中的静止质量能量的比率不高达几百,我们得出结论,在这项研究中看到的射流不是伽玛射线暴射流。在GRMHD模拟中,它表明,喷流是从祖的中心发射。我们还发现,质量吸积率发射后的喷气显示快速的时间变化,类似于一个典型的时间曲线的伽玛射线暴。我们发现,在喷流底部,每单位静止质量通量的能量通量高达10^2。因此,我们得出结论,大量的洛伦兹因子的射流可以是潜在的高时,它向外传播。我们还利用相对论流体动力学方法模拟了该星系的爆发核合成过程。发现56 Ni的量对能量沉积速率非常敏感。因此,即使总爆炸能量高达10^52 erg,合成的56 Ni也很少。我们的结论是,一些伽玛暴可以与暗超新星。

英文摘要:

I have developed two numerical codes to investigate the dynamics of collapsars. One is two-dimensional MHD code that are performed using the Newtonian (ZEUS-2D) code where realistic equation of state, neutrino cooling and heating processes are taken into account. The other one is two-dimensional general relativistic magnetohydrodynamic (GRMHD) code. I have performed numerical simulations of collapsars using these codes and realistic progenitor models. In the Newtonian code, it is found that neutrino heating processes are not efficient enough to launch a jet in this study. It is also found that a jet is launched mainly by toroidal fields that are amplified by the winding-up effect. However, since the ratio of total energy relative to the rest-mass energy in the jet is not as high as several hundred, we conclude that the jets seen in this study are not GRB jets. In the GRMHD simulation, it is shown that a jet is launched from the center of the progenitor. We also find that the mass accretion rate after the launch of the jet shows rapid time variability that resembles to a typical time profile of a GRB. We find that the energy flux per unit rest-mass flux is as high as 10^2 at the bottom of the jet. Thus we conclude that the bulk Lorentz factor of the jet can be potentially high when it propagates outward. We also performed two-dimensional relativistic hydrodynamic simulations of the collapsar model to investigate the explosive nucleosynthesis happened there. It is found that the amount of 56Ni is very sensitive to the energy deposition rate. Thus the synthesized 56Ni can be little even if the total explosion energy is as large as 10^52 erg. We conclude that some GRBs can associate with faint supernovae.

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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