伽玛暴多波段瞬时辐射机制研究

More and more robotic telescopes and large-diameter telescopes (including 2.4 meter and BOOTES-4 telescopes in Yunnan observatory ) begin to observe gamma-ray burst and more and more early observations from optical-infrared band, X-ray to gamma-ray band in gamma-ray bursts are available. The observations are very important to understand the mechanism of the prompt emission, the properties of emission region and the activities of central engine. In this proposal, we focus on the prompt emission in multi band related to the central engine activities, e.g., the prompt gamma-ray emission, X-ray flares and optical flashes characterized by internal shocks. Our study is undertaken to figure out the origin of prompt emission in different bands from radiation mechanism. The studies include the following points: (1)following the prompt optical and gamma-ray observations, study whether the optical emission can be produced by the cooling of electrons emitting gamma rays or the extrapolation toward lower energy of gamma-ray spectrum; (2) constrain the radius of emission region and Lorentz factor from the optical data with the cooling of electrons; (3) try to explain the origin of optical flashes accompanied by X-ray flare using electrons cooling and constrain the parameters of the underlying blast wave emission and emission region of X-ray flare; (4)combining the energy spectrum and the light curves in wide bands, study whether the emissions in different bands are from different regions.

随着国际国内越来越多的自动望远镜、大口径望远镜（包括云南天文台.2.4望远镜、BOOTES-4等）投入伽玛暴观测，越来越多的暴观测到早期从光学-红外、X射线到高能伽玛的宽波段辐射，这些多波段辐射对于理解伽玛暴瞬时辐射机制、辐射区性质、中心活动等至关重要。本项目着眼于与中心活动相关的瞬时辐射（包括暴阶段辐射、X射线耀发、内激波特征的光学闪等）的多波段行为，旨在从动力学和辐射机制角度解释各波段辐射的起源并限定辐射模型参数。具体的研究内容包括：（1）从暴阶段光学和伽玛辐射数据出发，研究光学能否通过电子的冷却或伽玛辐射能谱的低能延伸产生；（2）利用瞬时光学辐射区同步自吸收和电子的冷却来限制辐射区性质，如辐射区尺度和洛伦兹因子等；（3）研究X射线耀发辐射区电子的冷却能否产生同时的光学闪，并与观测数据比较，来限制辐射区参数；（4）结合宽波段能谱和各波段时变特征，研究各波段是否产生于不同的辐射区。

伽玛暴的辐射机制问题自伽玛暴发现以来一直未得到很好的解决，本项目主要围绕该问题进行研究。我们根据最近激波后粒子加速和磁场演化的数值模拟结果研究了伽玛暴内激波波后磁场衰减的情况下，电子在同步和逆康普顿散射共同冷却下所产生的辐射谱。我们发现这种情况下的同步谱可以较为自然地解释困扰我们多年的伽玛暴Band谱成因问题。我们还利用Fermi/LAT的高能伽玛观测数据与IceCube(后称IC)中微子探测器的观测结果，基于pp碰撞和p-gamma碰撞产生高能光子和高能中微子具有关联性的理论，共同限制IC观测到的TeV-PeV中微子的起源，我们发现寄主于星暴星系的GRB是最可能的中微子源。我们还利用丽江2.4米望远镜参与了对伽玛暴余辉的国际联测，与合作者共同获得了一批源的多波段数据,为研究伽玛暴余辉机制和暴周环境提供了重要的数据支持。我们还考虑了在伽玛暴这类高磁场、致密的天体中，同步辐射、同步自吸收和逆康普顿散射共同作用下的电子辐射情况。