Photospheric Prompt Emission From Long Gamma Ray Burst Simulations. II. Spectropolarimetry
Photospheric Prompt Emission From Long Gamma Ray Burst Simulations. II. Spectropolarimetry
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DOI：
10.3847/1538-4357/ac4093
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发表时间：
2021-08
期刊：
影响因子：
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通讯作者：
T. Parsotan;D. Lazzati
中科院分区：
文献类型：
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作者：
T. Parsotan;D. Lazzati
虽然伽玛射线暴（GRBs）已经被发现了几十年，但由于缺乏关于产生高能辐射闪光或瞬发辐射的辐射机制的知识，这些事件阻止了GRBs作为高能天体物理过程探测器的充分使用。虽然有多个模型试图描述即时发射，但每个模型都可以调整以解释伽马和X射线能带中观察到的GRB特性。一个能量范围，尚未充分探讨的目的，即时发射模型比较是光学波段，特别是关于偏振。在这里，我们使用一个改进的蒙特卡罗辐射传输代码来计算预期的光球光学和伽马射线偏振签名（分别为λ opt和λ γ）从一组两个相对论流体动力学长伽玛暴模拟，模拟恒定和可变喷流。我们发现，时间分辨的Ekopt可以很大（约75%），而时间积分的Ekopt可以较小，由于在伽玛射线暴喷流的不对称性，其中光子起源的积分; Ekopt γ遵循类似的演变与较小的偏振度Ekopt。我们还表明，在每个能量范围内，α-opt和α-γ与观测结果吻合得很好。此外，我们根据它们在米德关系中的位置对伽玛暴的预期极化进行了预测。虽然可以改进我们的分析和预测，他们表现出的洞察力，全球辐射传输模拟伽玛暴喷流可以提供相对于当前和未来的观测。
Although gamma ray bursts (GRBs) have been detected for many decades, the lack of knowledge regarding the radiation mechanism that produces the energetic flash of radiation, or prompt emission, from these events has prevented the full use of GRBs as probes of high-energy astrophysical processes. While there are multiple models that attempt to describe the prompt emission, each model can be tuned to account for observed GRB characteristics in the gamma and X-ray energy bands. One energy range that has not been fully explored for the purpose of prompt emission model comparison is that of the optical band, especially with regard to polarization. Here, we use an improved Monte Carlo radiation transfer code to calculate the expected photospheric optical and gamma-ray polarization signatures (Πopt and Π γ , respectively) from a set of two relativistic hydrodynamic long GRB simulations, which emulate a constant and variable jet. We find that time-resolved Πopt can be large (∼75%) while time-integrated Πopt can be smaller due to integration over the asymmetries in the GRB jet where optical photons originate; Π γ follows a similar evolution as Πopt with smaller polarization degrees. We also show that Πopt and Π γ agree well with observations in each energy range. Additionally, we make predictions for the expected polarization of GRBs based on their location within the Yonetoku relationship. While improvements can be made to our analyses and predictions, they exhibit the insight that global radiative transfer simulations of GRB jets can provide with respect to current and future observations.