论文标题

来自径向分层的离轴GRB流出的极化

Polarization From A Radially Stratified Off-Axis GRB Outflow

论文作者

Pedreira, A. C. Caligula do E. S., Fraija, N., Galvan-Gamez, A., Kamenetskaia, B. Betancourt, Dichiara, S., Dainotti, M. G., Becerra, R. L., Veres, P.

论文摘要

虽然主要的辐射机制伽马射线爆发(GRB)仍然是一个争论的问题,但同步加速器发射是描述多波长余辉观测的最重要的候选者之一。因此,预计GRB应在其演化中呈现一定程度的极化 - 提出了一种可行的方法,可以探测这些爆发的能量和角度特性。尽管由于GRB观察的固有复杂性,正在取得进步,并且同步基因极化的理论建模现在比以往任何时候都更加相关。在此手稿中,我们介绍了一个受托模型的极化,其中辐射分层的离轴流出径流描述了辐射 - 绝热状态中的同步转移发射的发射。这是通过幂律速度分布进行参数化的,并在恒定密度和类似风的外部环境中减速。我们将这种理论极化模型应用于选定的爆发,这些爆发呈现出余波发射的证据,包括Neil Gehrels Swift天文台观察到的最接近的孤儿GRB候选者和一些可能产生电磁发射的引力波(GWS)事件。对于GRB 170817a,我们需要无线电波长中可用的极化上限来限制其磁场几何形状。

While the dominant radiation mechanism gamma-ray bursts (GRBs) remains a question of debate, synchrotron emission is one of the foremost candidates to describe the multi-wavelength afterglow observations. As such, it is expected that GRBs should present some degree of polarization across their evolution - presenting a feasible means of probing these bursts' energetic and angular properties. Although obtaining polarization data is difficult due to the inherent complexities regarding GRB observations, advances are being made, and theoretical modeling of synchrotron polarization is now more relevant than ever. In this manuscript, we present the polarization for a fiduciary model where the synchrotron forward-shock emission evolving in the radiative-adiabatic regime is described by a radially stratified off-axis outflow. This is parameterized with a power-law velocity distribution and decelerated in a constant-density and wind-like external environment. We apply this theoretical polarization model for selected bursts presenting evidence of off-axis afterglow emission, including the nearest orphan GRB candidates observed by the Neil Gehrels Swift Observatory and a few Gravitational Wave (GWs) events that could generate electromagnetic emission. In the case of GRB 170817A, we require the available polarimetric upper limits in radio wavelengths to constrain its magnetic field geometry.

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