基于辐射机制模型的伽玛暴能谱分析和喷流辐射区的物理性质研究

Although broadband observations with the Fermi satellite has greatly improved our understanding on the radiation mechanisms and physical properties of the radiation regions, the radiation mechanisms of GRBs remains an open question. Different from previous routine, which uses a model that composes of the Band function and an extra radiation component to make spectral fits for the prompt gamma-ray spectra, we directly employ physical radiation models to fit the observed GRB spectra and study the compositions and radiation mechanisms as well as relations among the magnetization factor, radiation efficiency, and initial Lorentz factor of GRB outflows. The research contents are as following. Firstly, we will systematically process the data of Fermi GRBs and present a large database of the Fermi GRB spectra, then fit the spectra with a model that composes of multi-color blackbody spectrum and a synchrotron radiation spectrum in the framework of the baryonic fireball models and investigate the possible relations between the model parameters and observables. Next, in the scenario of Poynting-flux-dominated jet models, we fit the spectra with the synchrotron radiation models by setting the magnetic field strength and the magnetization factor as free parameters and reveal their possible relations to the radiating electron spectrum and observables. We also compile a sample of broadband spectra in the optical, X-ray, and GeV gamma-ray band in order to examine the GeV afterglows are from synchrotron radiation or from inverse Compton scattering process and study the radiation efficiency of these GRBs.

Fermi卫星的宽能段观测极大地丰富了人们对伽玛暴辐射机制和辐射区物理性质的认识，然而伽玛暴辐射机制问题至今未解。本项目抛弃经验的“Band 函数+其它辐射成分”模型，而直接采用物理模型谱拟合观测能谱，进而研究伽玛暴喷流的物质组份、辐射机制，揭示喷流磁化因子与辐射效率、火球洛伦兹因子之间的关联性。研究内容：系统处理Fermi卫星探测到的伽玛暴，构建大样本的伽玛暴宽波段能谱观测数据库；重子火球模型下，用多色黑体谱+同步辐射谱拟合宽波段能谱，并分析其模型参数与观测量之间的关联性；在磁化喷流模型下，引入磁化因子、磁场演化作为自由参数拟合观测谱，给出辐射电子谱、磁化因子，理解磁化因子与辐射电子谱及各种观测量之间的关联性；构建伽玛暴余辉从光学、X射线到GeV能段的宽波段能谱，探究GeV能段余辉辐射是同步辐射主导还是逆康普顿过程主导，并研究火球的辐射效率。

Fermi卫星的宽波段观测极大地丰富了人们对伽玛暴辐射机制和辐射区物理性质的认识，考虑伽玛暴辐射机制问题至今未解。本项目抛弃经验的“Band 函数+其它辐射成分”模型，而直接采用物理模型谱拟合观测能谱，进而研究伽玛暴喷流的物质组份、辐射机制，揭示喷流磁化因子与辐射效率、火球洛伦兹因子之间的关联性。具体内容有：（1）通过对极亮伽玛暴GRB160625B进行多波段数据处理，找到了其作为长时期喷流喷出物演化的证据。（2）对伽玛暴GRB 181225A中的谱演化行为进行了分析研究。（3）基于多色黑体谱模型对伽玛暴瞬时辐射阶段的时间积分谱进行分析，研究伽玛暴瞬时辐射中热成分存在的依据。（4）对伽玛暴瞬时辐射谱进行精细的时间分辨谱分析，用黑体模型进行拟合，研究瞬时辐射过程中的热成分及其演化情况。（5）伽玛暴谱延迟与峰值能量演化之间的相关分析。（6）研究分析了多脉冲伽玛暴洛伦兹因子的演化问题，借以理解伽玛暴爆发进程中的运动问题，分析伽玛暴的本征物理问题。