同步辐射和费米伽马暴光谱的一致性检验

定义了一个新的量,曲率宽度,去检查同步模型与伽玛射线暴(GRB)光谱的一致性.此量用于测量GRB中辐射能谱(νFν,ν和Fν分别是频率和随频率变化的能量流量)峰值处的光谱拐折锐度.然后使用它检查了理论同步模型与观测到的GRB光谱之间的一致性.首先计算几种典型的同步模型的曲率宽度,包括单能、单幂律和拐折幂律电子同步模型.其次从Fermi/GBM (Gamma-ray Burst Monitor)长GRB时间分辨光谱目录中选择包含1198个光谱的GRB样本,将光谱与常用的经验模型拟合,并计算最佳拟合模型的光谱曲率宽度.通过比较两个曲率宽度,发现大多数样本与同步模型不一致,因为同步模型的光谱拐折比数据的光谱拐折更加平滑.结果表明同步模型很难适合大多数观测到的GRB光谱.此外,在暴脉冲中发现光子流量和曲率宽度之间存在强的反相关性,这表明流量越高,光谱拐折越尖锐,或者与同步模型的偏差就越大.

A Consistency Check of Synchrotron Radiation with Fermi GRB Spectra

We define a new quantity, the curvature width, to check the consistency of the synchrotron model with the spectra of gamma-ray bursts (GRBs). This quantity measures the spectral break sharpness at the emission energy spectral ( vFv, v is frequency and F v is energy flux as a function of v) peak in GRBs. Using this quantity, we check the consistency between the theoretical synchrotron model and the observed GRB spectra. We first calculate the curvature widths of several typical synchrotron models including the mono-energetic, single power-law and broken power-law electron synchrotron models. Then we choose a GRB sample including a total of 1198 spectra from the Fermi/GBM (Gamma-ray Burst Monitor) long GRB time-resolved spectra catalog, fit the spectra with commonly used empirical models and compute the spectral curvature widths of best-fit models. By comparing the two curvature widths, we find most of the sample are incompatible with the synchrotron models, because the spectral breaks of the synchrotron models are much smoother than those of the data. Our results suggest that the synchrotron models are hard to accommodate most of the observed GRB spectra. Further, a tight anti-correlation between the photon flux and curvature width is found within a pulse of a burst, which suggests the higher flux, the sharper spectral break or the more deviating from the synchrotron models.