JET PROPAGATIONS, BREAKOUTS, AND PHOTOSPHERIC EMISSIONS IN COLLAPSING MASSIVE PROGENITORS OF LONG-DURATION GAMMA-RAY BURSTS
JET PROPAGATIONS, BREAKOUTS, AND PHOTOSPHERIC EMISSIONS IN COLLAPSING MASSIVE PROGENITORS OF LONG-DURATION GAMMA-RAY BURSTS
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DOI：
10.1088/0004-637x/731/2/80
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发表时间：
2010-09
期刊：
影响因子：
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通讯作者：
H. Nagakura;Hirotaka Ito;K. Kiuchi;S. Yamada
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文献类型：
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作者：
H. Nagakura;Hirotaka Ito;K. Kiuchi;S. Yamada
我们通过二维轴对称相对论流体动力学模拟研究了：（1）喷流通过快速旋转和坍缩的大质量星星的包层的传播，这被认为是长持续时间伽马射线暴（GRB）的祖先;（2）爆发和随后的恒星风膨胀;（3）伴随的光球辐射。我们发现，如果信封均匀旋转几乎在质量脱落的限制，其外部最终停止收缩时，离心力变得足够大。然后，另一个冲击波形成，向外传播，并打破了信封进入恒星风。射流或离心反弹诱导激波是否提前爆发取决于射流喷射的时机。如果激波爆发发生得较早，由于较晚的注入，喷流传播和随后的光球发射受到很大的影响。我们特别注意的观测结果的差异喷射喷射的时间。我们计算光学深度，找到光球的位置，提取密度，并在适当的延迟时间从流体动力学数据的温度。我们发现，光球辐射的光度和观测温度都比以前的研究报道的要低得多。虽然亮度仍然足够高的伽玛暴，观测到的温度低于米德关系预期的光谱峰值的能量。这可能意味着光子和物质之间的能量交换在更深的内部终止，或者一些非热过程正在运作以提高光子能量。
We investigate the following by two-dimensional axisymmetric relativistic hydrodynamical simulations: (1) jet propagations through an envelope of a rapidly rotating and collapsing massive star, which is supposed to be a progenitor of long-duration gamma-ray bursts (GRBs); (2) breakouts and subsequent expansions into stellar winds; and (3) the accompanying photospheric emissions. We find that if the envelope rotates uniformly almost at the mass shedding limit, its outer part eventually stops contracting when the centrifugal force becomes large enough. Then another shock wave is formed, propagates outward, and breaks out of the envelope into the stellar wind. Whether the jet or the centrifugal bounce-induced shock breaks out earlier depends on the timing of jet injection. If the shock breakout occurs earlier, owing to a later injection, the jet propagation and subsequent photospheric emissions are affected substantially. We pay particular attention to observational consequences of the difference in the timing of jet injection. We calculate optical depths to find the location of photospheres, extracting densities, and temperatures at appropriate retarded times from the hydrodynamical data. We show that the luminosity and observed temperature of the photospheric emissions are both much lower than those reported in previous studies. Although luminosities are still high enough for GRBs, the observed temperatures are lower than the energy at the spectral peak expected by the Yonetoku relation. This may imply that energy exchanges between photons and matter are terminated deeper inside or that some non-thermal processes are operating to boost photon energies.