利用重子载荷约束GRB 170817 A的喷流发射时间
Constraining the Jet Launching Time of GRB 170817A by Utilizing the Baryon Loading
摘要：
观测到的GRB 170817 A相对于GW 170817的延迟携带了关于伽马射线暴（GRB）物理学的重要信息，并受到激烈的争论。在这封信中，我们提出了一种方法来讨论这种时间延迟的主要来源。首先，我们使用结构喷流模型来拟合GRB 170817 A的X射线/光学/射电余辉以及由甚长基线干涉测量的超光速运动。我们的结构喷流模型与角度相关的能量和重子加载。结果表明，我们的模型能很好地拟合GRB 170817 A的余辉。在此基础上，根据拟合结果推断了喷注中的重子载荷。通过比较不同阶段的重子负荷与质量外流，我们推断喷流发射相对于合并的时滞小于几百或几十毫秒。这表明GRB 170817 A相对于GW 170817的时间延迟主要由射流传播到其耗散半径的扩展时间定义。
英文摘要：
The observed delay of GRB 170817A relative to GW170817 carries significant information about gamma-ray burst (GRB) physics and is subject to intense debate. In this letter, we put forward an approach to discuss the major source of this time delay. First of all, we use the structured jet model to fit the X-ray/optical/radio afterglows of GRB 170817A together with superluminal motion measured by the Very Long Baseline Interferometry. Our structured jet is modelled with angle-dependent energy and baryon loading. It is found that our model can well fit the afterglows of GRB 170817A. After that, the baryon loading in the jet is inferred based on our fitting results. By comparing the baryon loading to the mass outflow in different stages, we infer that the time lag of the jet launch relative to the merger is less than hundreds or tens of milliseconds. It suggests that the time delay of GRB 170817A relative to GW170817 is defined mostly by the spreading time of the jet propagating to its dissipation radius.
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