Jet Dynamics in Compact Object Mergers: GW170817 Likely Had a Successful Jet
Jet Dynamics in Compact Object Mergers: GW170817 Likely Had a Successful Jet
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DOI：
10.3847/1538-4357/aae084
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发表时间：
2018-06
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影响因子：
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通讯作者：
P. Duffell;E. Quataert;D. Kasen;Hannah Klion
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文献类型：
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作者：
P. Duffell;E. Quataert;D. Kasen;Hannah Klion
本文采用相对论流体力学数值计算方法研究了双中子星合并过程中射流与同源流出物之间的相互作用。我们量化了射流传递的热能和射流逃离抛射物的能力如何取决于喷气发动机和抛射物的参数。在我们的假设下，与发动机持续时间相比，准直射流在早期开始，我们表明成功突破前茧激波需要一个成功逃离弹射的射流。这是因为喷射物正在膨胀，而失败的射流的前向激波在到达喷射物边缘之前就停止了。这个结论只有在高能广角喷流中才能被规避，而这些喷流的参数在短时间的GRB观测中是不舒服的。对于成功的喷流，我们发现喷流爆发有两种状态：早期爆发在时间尺度上短于发动机持续时间，而后期爆发在发动机关闭后。一个较晚的爆发可以解释GW170817中引力波和伽马射线之间观察到的延迟。我们表明，对于这里调查的射流参数的整个参数空间（覆盖能量~ 1048-1051 erg和开口角θj ~ 0.07-0.4），射流沉积的热能在第二时间尺度上至少比r-过程加热产生的热能少一个数量级。因此，激波加热在确定与中子星合并（千新星）相一致的热能量瞬变的光度时在能量上是次要的。
We use relativistic hydrodynamic numerical calculations to study the interaction between a jet and a homologous outflow produced dynamically during binary neutron star mergers. We quantify how the thermal energy imparted by the jet and the ability of the jet to escape the ejecta depend on the parameters of the jet engine and the ejecta. Under our assumptions, a collimated jet initiated at early times compared to the engine duration, we show that successful breakout of the forward cocoon shock necessitates a jet that successfully escapes the ejecta. This is because the ejecta is expanding, and the forward shock from a failed jet stalls before it reaches the edge of the ejecta. This conclusion can be circumvented only for very energetic wide angle jets, with parameters that are uncomfortable given short-duration GRB observations. For successful jets, we find two regimes of jet breakout from the ejecta: early breakout on timescales shorter than the engine duration, and late breakout well after the engine shuts off. A late breakout can explain the observed delay between gravitational waves and gamma rays in GW170817. We show that for the entire parameter space of jet parameters surveyed here (covering energies ∼1048–1051 erg and opening angles θj ∼ 0.07–0.4) the thermal energy deposited by the jet is less than that produced by r-process heating on second timescales by at least an order of magnitude. Shock heating is thus energetically subdominant in setting the luminosity of thermally powered transients coincident with neutron star mergers (kilonovae).