伽玛射线暴（GRB）是发生在宇宙当中最剧烈的天体活动过程,是当今高能天体物理学最活跃的研究领域之一。自上世纪六十年代末首次发现GRB以来，经过近半个世纪的努力研究，不管在实验上和理论上都有了突破性的进展。但是对一些最基本的问题，特别是GRB的中心引擎问题还不十分清楚。通过研究GRB光子的极化可以使我们对它的中心引擎有一个更加深入的了解。本申请项目旨在对GRB极化做详细的理论研究，继而深入探讨GRB的中心引擎。我国计划于2016年随着天宫II号空间站发射一个高精度的伽玛射线极化探测器POLAR，它的科学目标是精确测量GRB光子的极化。我们的研究项目与POLAR探测器紧密相结合。首先我们从理论上研究GRB各种可能的爆发机制及其不同极化特性。然后把理论计算与POLAR探测器观测到的极化数据进行比较，挑选出最有可能的GRB模型并且限制模型参数，从而为进一步揭示GRB的中心引擎奠定基础。

Gamma-ray burst (GRB) is the most energetic explosion in the universe, and it is one of the most active research fields in modern high-energy astrophysics. Since the first discovery of GRB at the end of 1960s, many breakthroughs have been achieved in both the observational and theoretical aspects in the past half century. However, some of the most basic problems, especially the central engine, are still not very clearly understood. The research on GRB polarization provides a deep insight into the central engine. This project aims to do a detailed theoretical study on the polarization of GRB, and then further explore the central engine problem. China plans to launch a high-precious gamma-ray polarization detector named POLAR in 2016 onboard the space laboratory Tiangong II. The aim of POLAR is to accurately measure the polarization of GRB photons. Our research closely cooperates with the POLAR detector. First, we theoretically study the possible GRB explosion mechanisms and their polarization properties. Then, we compare our theoretical calculations with the observational data of POLAR, to select out the most possible model and at the same time to constrain the model parameters, hence laying the foundation for further revealing the central engine.