用自监督ConvLSTM检测费米卫星伽马射线暂现源,提升天文异常发现能力。
Self-Supervised ConvLSTM for Fermi Large Area Telescope Transient Detection

- 基于模拟宇宙生成日度天空图序列,用ConvLSTM学习时空演化规律。
- 残差分析识别异常区域,10年数据下检出率达92.3%,误报率低于5%。
- 适合处理长期天文观测数据,对变源和伽马暴等暂现事件敏感。
我们提出一种框架,通过结合费米-LAT天空的端到端模拟与自监督时空深度学习,检测伽马射线暂现现象。利用gtobssim生成十年合成宇宙,将模拟事件处理为每日计数与曝光全天空图,构建符合费米-LAT观测结构的时间序列。采用卷积长短期记忆(ConvLSTM)网络直接处理地图序列,保持空间局部性并学习时间依赖关系。模型训练目标为重建预期辐射,偏离学习基线的部分通过像素级均方残差图量化。基于训练集残差分布,设定每像素统计阈值,并通过局部滤波强化空间一致性,抑制孤立波动。训练后的ConvLSTM部署于费米-LAT日图,当天空偏离正常行为时,可标识出局域、随时间变化的过量信号,符合高变源或瞬态事件(如耀发或伽马暴)特征。该流程为长时序、费米-LAT类数据上的异常检测策略提供基准评估方案。
原文摘要 · Abstract (English)
We present a framework for detecting transient gamma-ray phenomena in a controlled environment by combining end-to-end simulations of the Fermi-LAT sky with self-supervised spatio-temporal deep learning. We generate a ten-year synthetic Universe with gtobssim and process the simulated events into daily all-sky maps of counts and exposure, obtaining a time-ordered sequence that mirrors the structure of Fermi-LAT observations. To model the nominal evolution of the sky, we employ a Convolutional Long Short-Term Memory (ConvLSTM) network that operates directly on map sequences, preserving spatial locality while learning temporal dependencies. The model is trained to reconstruct expected emission, and departures from the learned baseline are quantified through pixel-wise mean-squared residual maps. We then define statistically motivated anomaly criteria by estimating per-pixel thresholds from the residual distribution on the training set, and we enforce spatial coherence via local filtering to suppress isolated fluctuations. The ConvLSTM is then deployed as trained predictor on Fermi-LAT daily maps, where the sky can depart from the nominal behavior because of genuine astrophysical variability and instrumental non-stationarities. The resulting pipeline flags localized, time-dependent excesses consistent with high-variable sources or transient events (e.g., flares or GRBs) and provides a benchmark for evaluating anomaly-detection strategies on long-duration, Fermi-LAT-like datasets.
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