GRB 170817A 瞬时伽马射线光变曲线中的非平稳随机时标特征
Nonstationary Stochastic Timing Signatures in the Prompt Gamma-Ray Light Curve of GRB 170817A
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中文总结 AI 辅助
该研究用变点模型和深度核 GP 模型分析 GRB 170817A 的伽马射线光变曲线，识别出协方差转变与时间变形特征，支持分段协方差演化，需进一步校准评估非平稳结构的稳健性与物理起源。
中文摘要 AI 辅助
我们使用变点模型和深度核高斯过程（GP）模型研究 GRB 170817A 微弱瞬时伽马射线辐射中的随时间变化的随机结构，分析基于费米伽马射线暴监视器（Fermi/GBM）10-300 keV 能段、时间分辨率为 0.10 s 的光变曲线。两种变点构型在引力波并合后 0.269 s 和 0.237 s 处识别出相似的协方差转变，对应的 10%-90% 转变宽度分别为 0.441 s 和 0.393 s。在代表性的门控边界 t_tr = 0.27 s 处，所有四种固定分割分配均产生比全曝光平稳 Matern-3/2 参考模型更高的证据增益，其中最大增益为 Matern-3/2 到 Matern-3/2 分配的 Δ ln Z_split = 5.72 ± 0.16，门控匹配的阻尼随机游走（DRW）到 Matern-3/2 分配的 Δ ln Z_split = 5.50 ± 0.16，该固定分割比较支持分段特定的协方差演化，无需改变协方差族。深度核模型恢复了局域化的时间变形特征，对于 DRW 和 Matern-3/2 基核，峰值分别出现在并合后 1.65 s 和 1.75 s，它们与采用的伽马射线起始时间 1.74 s 的偏移分别为 -0.09 s 和 +0.01 s，均在 0.10 s 采样分辨率内。当分箱宽度从 0.10 s 变为 0.12 s 时，全波段时标特征保持稳定，而能量细分产生的门控位置偏移大于变形峰值偏移。残差诊断显示模型能重现主导时间结构，但仍存在局域化残差依赖。我们将门控定义的协方差转变和局域化时间变形特征解释为模型依赖的唯象时标诊断，需要进一步的模拟校准和计数级建模来评估所恢复的非平稳结构的统计稳健性和物理起源。
英文摘要
We investigate time-dependent stochastic structure in the weak prompt gamma-ray emission of GRB 170817A using change-point and deep-kernel Gaussian-process (GP) models. The analysis is based on the 10-300 keV Fermi/GBM light curve with 0.10 s time resolution. Two change-point configurations identify similar covariance transitions at 0.269 and 0.237 s after the gravitational-wave merger, with 10-90% transition widths of 0.441 and 0.393 s, respectively. At the representative gate-defined boundary of t_tr = 0.27 s, all four fixed-split assignments yield positive evidence gains over the full-exposure stationary Matern-3/2 reference. The largest gain is Delta ln Z_split = 5.72 +/- 0.16 for the Matern-3/2 to Matern-3/2 assignment, while the gate-matched damped random walk (DRW) to Matern-3/2 assignment gives Delta ln Z_split = 5.50 +/- 0.16. The fixed-split comparison therefore supports segment-specific covariance evolution without requiring a change of covariance family. The deep-kernel models recover localized time-deformation features peaking at 1.65 and 1.75 s after the merger for DRW and Matern-3/2 base kernels, respectively. Their offsets from the adopted gamma-ray onset at 1.74 s are -0.09 and +0.01 s, both within the 0.10 s sampling resolution. The full-band timing features remain stable when the bin width is changed from 0.10 to 0.12 s, whereas energy subdivision produces larger shifts in gate locations than in warp peaks. Residual diagnostics show that the models reproduce the dominant temporal structure, although localized residual dependence remains. We interpret the gate-defined covariance transition and the localized time-deformation feature as model-dependent phenomenological timing diagnostics. Further simulation calibration and count-level modelling are needed to assess the statistical robustness and physical origin of the recovered nonstationary structure.
发表机构
- School of Physics and Astronomy, Yunnan University（云南大学物理与天文学院）
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