使用平滑拐折幂率(Smoothly Broken Power Law,SBPL)模型、折线幂率(Broken Power Law,BPL)模型和波段函数(Band)模型拟合8个费米(Fermi)亮暴,得到165个最佳模型拟合谱,然后根据这165个谱的能量流量得出3个模型拟合数据的范围和一些结...使用平滑拐折幂率(Smoothly Broken Power Law,SBPL)模型、折线幂率(Broken Power Law,BPL)模型和波段函数(Band)模型拟合8个费米(Fermi)亮暴,得到165个最佳模型拟合谱,然后根据这165个谱的能量流量得出3个模型拟合数据的范围和一些结论。折线幂率模型能很好地拟合较暗的暴(F e<5×10^-5 erg·cm^-2),而较亮的暴用波段函数模型(5×10^-5 erg·cm^-2<F e<2.0×10^-4 erg·cm^-2)和平滑拐折幂率模型(2.0×10^-4 erg·cm^-2<F e<3.8×10^-4 erg·cm^-2)可以得到更好的拟合结果。样本中大约一半的谱用折线幂率模型拟合较好,表明有些较暗的暴的谱形接近折线形状,即谱拐折比较尖锐。虽然多数光谱中最佳拟合模型是折线幂率模型,但波段函数模型和平滑拐折幂率模型拟合也能得到可以接受的结果,并且高能光子少以至于现有的数据不能很好地排除一些能谱模型。另外,目前的拟合结果可能受到仪器响应矩阵的影响,不能很好地确定真实的物理模型,也就是说伽玛暴谱看似能被模型解释,但可能不是真实的。展开更多
GRB 131231A是一个具有E_(P)和α“双追踪”行为的特殊暴。为了进一步分析该暴的能谱特征,使用贝叶斯方法做详细的时间分辨光谱分析后发现,24个分辨谱中16个有明显热成分,这些热成分主要分布在脉冲的前期和峰值附近,支持伽马暴喷流从物...GRB 131231A是一个具有E_(P)和α“双追踪”行为的特殊暴。为了进一步分析该暴的能谱特征,使用贝叶斯方法做详细的时间分辨光谱分析后发现,24个分辨谱中16个有明显热成分,这些热成分主要分布在脉冲的前期和峰值附近,支持伽马暴喷流从物质主导到磁主导的过渡。加入热成分后参数E_(P)和α都变硬,而峰值流量F_(p)几乎不变。使用光球层成分计算相对论流出物的特性参数后发现,流出物特性参数初始半径r_(0)、饱和层半径r_(s)、光球层半径r_(ph)和流出物滑行运动阶段洛伦兹因子Γ均发生较为明显的演化;温度随时间的演化能用拐折幂律模型拟合,上升和下降阶段的幂律指数分别为a=7.65±3.48和b=-2.10±3.48,下降指数b与前人得出的约-2/3有较大偏差。展开更多
Multifractal spectrum, autocorrelation/semivariogram and power spectrum are three dif- ferent functions characterizing a field or measure from different aspects. These functions are interre- lated in such that the aut...Multifractal spectrum, autocorrelation/semivariogram and power spectrum are three dif- ferent functions characterizing a field or measure from different aspects. These functions are interre- lated in such that the autocorrelation/semivariogram and power spectrum are related to the low order statistical moments (0 to 2 nd) which may determine the local multifractality (τ ″(1)) of a multifractal measure. A better understanding of the interrelationships among these three functions is important because, on one hand, the multifractal modelling characterizes a multifractal measure in a more de- tailed manner since it involves moments of all orders. On the other hand, the commonly used semivariogram and power spectrum functions can be used as alternatives to study the dominant mul- tifractal properties around the mean measure. Moreover, semivariogram and power-spectrum func- tions provide spatial and spectral information, which is highly valued in geological applications. A new fractal relation found between area and power-spectrum will be useful for investigation of new meth- ods of spatial-spectral analysis for pattern recognition, anomaly separation, classification, etc. These results have been demonstrated with the case study of modelling gamma ray spectrometer data from the mineral district, southwestern Nova Scotia, Canada. The results have shown that the values of uranium (U), thorium (Th) and potassium (K) may possess monofractal properties whereas the ratios of these values show high multifractality. The values of the ratios U/K and U/Th show relatively large variances and may provide more information for distinguishing the distinct phases of the granites, country rocks as well as possible gold mineralization-associated regional hydrothermal alteration zones. In addition, the power spectra for U, Th, K, U/Th and U/K consistently show two distinct power-law relationships for two ranges of wave number 12≤ω ≤160 km and 0≤ω ≤12 km. These properties might provide useful thresholds for separating the power-spectrum values into two types of patterns to reflect different influences of possible geological processes such as hydrothermal altera- tion in the study area.展开更多
文摘Multifractal spectrum, autocorrelation/semivariogram and power spectrum are three dif- ferent functions characterizing a field or measure from different aspects. These functions are interre- lated in such that the autocorrelation/semivariogram and power spectrum are related to the low order statistical moments (0 to 2 nd) which may determine the local multifractality (τ ″(1)) of a multifractal measure. A better understanding of the interrelationships among these three functions is important because, on one hand, the multifractal modelling characterizes a multifractal measure in a more de- tailed manner since it involves moments of all orders. On the other hand, the commonly used semivariogram and power spectrum functions can be used as alternatives to study the dominant mul- tifractal properties around the mean measure. Moreover, semivariogram and power-spectrum func- tions provide spatial and spectral information, which is highly valued in geological applications. A new fractal relation found between area and power-spectrum will be useful for investigation of new meth- ods of spatial-spectral analysis for pattern recognition, anomaly separation, classification, etc. These results have been demonstrated with the case study of modelling gamma ray spectrometer data from the mineral district, southwestern Nova Scotia, Canada. The results have shown that the values of uranium (U), thorium (Th) and potassium (K) may possess monofractal properties whereas the ratios of these values show high multifractality. The values of the ratios U/K and U/Th show relatively large variances and may provide more information for distinguishing the distinct phases of the granites, country rocks as well as possible gold mineralization-associated regional hydrothermal alteration zones. In addition, the power spectra for U, Th, K, U/Th and U/K consistently show two distinct power-law relationships for two ranges of wave number 12≤ω ≤160 km and 0≤ω ≤12 km. These properties might provide useful thresholds for separating the power-spectrum values into two types of patterns to reflect different influences of possible geological processes such as hydrothermal altera- tion in the study area.
