Simulation-based spectral analysis of X-ray CCD data affected by photon pile-up
Simulation-based spectral analysis of X-ray CCD data affected by photon pile-up
复制标题
基于仿真的受光子堆积影响的 X 射线 CCD 数据的光谱分析
DOI：
10.1093/pasj/psab131
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发表时间：
2022
影响因子：
2.3
通讯作者：
et al.
中科院分区：
文献类型：
--
作者：
Tamba Tsubasa;Mori Koji;et al.
我们开发了一种基于模拟的光谱分析方法，用于分析受堆积影响的 X 射线 CCD 数据，而不会丢失任何光子统计数据。由于光子堆积的影响表现为复杂的非线性探测器响应，我们采用详细的模拟来计算 X 射线观测中的重要过程，包括物理相互作用、探测器信号生成、探测器读出和一系列数据缩减过程。这种模拟自然地再现了 X 射线和类背景事件，作为 X 射线光子在单个像素或相邻像素块中合并的结果，使我们能够构建一个非线性光谱分析框架，可以处理受堆积影响的观测数据。为了验证，我们使用该框架和探测器模拟的各种参数对朱雀 X 射线成像光谱仪 (XIS) 观测进行了数据分析，所有这些参数都针对该仪器进行了优化。我们提出了三种不同堆积程度的情况：PKS 2155−304（可忽略堆积）、Aquila X-1（中度堆积）和蟹状星云（强堆积）；我们表明，对于可忽略的堆积条件，非线性分析方法产生的结果与传统线性分析一致，并且准确地校正了众所周知的堆积效应，例如堆积情况下的光谱硬化和通量减少。这些校正结果与广泛使用的核心排除方法或具有更高定时分辨率（无堆积）的其他天文台获得的结果一致。通过适当优化模拟参数，我们的框架适用于用于 X 射线天文学的任何类型的 CCD，包括未来的任务，例如 X 射线成像和光谱任务 (XRISM)。
We have developed a simulation-based method of spectral analysis for pile-up-affected data of X-ray CCDs without any loss of photon statistics. As effects of the photon pile-up appear as complicated nonlinear detector responses, we employ a detailed simulation to calculate the important processes in an X-ray observation including physical interactions, detector signal generation, detector readout, and a series of data reduction processes. This simulation naturally reproduces X-ray-like and background-like events as results of X-ray photon merging in a single pixel or in a chunk of adjacent pixels, allowing us to construct a nonlinear spectral analysis framework that can treat pile-up-affected observation data. For validation, we have performed data analysis of Suzaku X-ray Imaging Spectrometer (XIS) observations using this framework with various parameters of the detector simulation, all of which are optimized for that instrument. We present three cases of different pile-up degrees: PKS 2155−304 (negligible pile-up), Aquila X-1 (moderate pile-up), and the Crab Nebula (strong pile-up); we show that the nonlinear analysis method produces results consistent with a conventional linear analysis for the negligible pile-up condition, and accurately corrects well-known pile-up effects such as spectral hardening and flux decrease for the pile-up cases. These corrected results are consistent with those obtained by a widely used core-exclusion method or by other observatories with much higher timing resolutions (without pile-up). Our framework is applicable to any types of CCDs used for X-ray astronomy, including future missions such as X-ray Imaging and Spectroscopy Mission (XRISM), by appropriate optimization of the simulation parameters.