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arXiv 1901.04719astro-ph.HE
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用POLAR和GBM的时间分辨GRB极化

Time-Resolved GRB Polarization with POLAR and GBM

J. Michael Burgess, M. Kole, F. Berlato, J. Greiner, G. Vianello, N. Produit, Z. H Li, J. C Sun

摘要:

同时对伽马射线暴(GRB)光谱和偏振进行$γ$射线测量提供了一种独特的方法来确定这些物体中的潜在发射机制,以及探测导致观测到的$γ$射线发射的粒子加速机制。在这里,我们检查联合观察到的数据从GRB 170114 A的POLAR和GBM,以确定其光谱和偏振特性,并试图了解产生这些观测的发射过程。我们的目标是开发一个可扩展的和统计上健全的框架,这些类型的测量适用于其他工具。我们利用现有的3 ML分析框架来开发一个新的分析管道,用于同时对光谱和偏振数据进行建模。我们推导出适当的泊松似然$γ$ -射线偏振测量中存在的背景。开发的框架是公开的类似测量与其他$γ$ -射线旋光仪。在贝叶斯概率背景下的数据进行分析,从两个仪器的光谱数据同时建模与物理,数值同步加速器代码。的光谱建模的数据是一致的同步加速器光子模型已被发现在大多数类似的单脉冲伽玛暴分析。极化结果揭示了随着时间的推移极化增长的轻微趋势,在发射的时间峰值处达到~30%的值。此外,观察到偏振角在整个发射过程中随时间演变。这些结果暗示同步辐射源的排放,但许多伽玛射线暴的进一步观测需要验证这些演变趋势。此外,我们鼓励开发时间分辨的极化模型的即时发射的伽玛射线暴,因为目前的模型是不够的预测,使我们目前的数据的完整建模。

英文摘要:

Simultaneous $γ$-ray measurements of gamma-ray burst (GRB) spectra and polarization offer a unique way to determine the underlying emission mechanism(s) in these objects as well as probing the particle acceleration mechanism(s) that lead to the observed $γ$-ray emission. Herein we examine the jointly-observed data from POLAR and GBM of GRB 170114A to determine its spectral and polarization properties and seek to understand the emission processes that generate these observations. We aim to develop an extensible and statistically sound framework for these types of measurements applicable to other instruments. We leverage the existing 3ML analysis framework to develop a new analysis pipeline for simultaneously modeling the spectral and polarization data. We derive the proper Poisson likelihood for $γ$-ray polarization measurements in the presence of background. The developed framework is publicly available for similar measurements with other $γ$-ray polarimeters. The data are analyzed within a Bayesian probabilistic context and the spectral data from both instruments are simultaneously modeled with a physical, numerical synchrotron code. The spectral modeling of the data is consistent with a synchrotron photon model as has been found in a majority of similarly analyzed single-pulse GRBs. The polarization results reveal a slight trend of growing polarization in time reaching values of ~30% at the temporal peak of the emission. Additionally, it is observed that the polarization angle evolves with time throughout the emission. These results hint at a synchrotron origin of the emission but further observations of many GRBs are required to verify these evolutionary trends. Furthermore, we encourage the development of time-resolved polarization models for the prompt emission of GRBs as the current models are not predictive enough to enable a full modeling of our current data.

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