Spatial and temporal variations of the <i>Chandra</i> ACIS particle-induced background and development of a spectral-model generation tool
Spatial and temporal variations of the <i>Chandra</i> ACIS particle-induced background and development of a spectral-model generation tool
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<i>Chandra</i> ACIS 粒子引起的背景的空间和时间变化以及光谱模型生成工具的开发
DOI：
10.1051/0004-6361/202141458
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Bamba A.
中科院分区：
文献类型：
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作者：
Suzuki H.;Plucinsky P. P.;Gaetz T. J.;Bamba A.
在X射线观测中，估计粒子诱导的背景是很重要的，特别是对于微弱和/或漫射源。虽然软件存在，（天空和探测器）背景数据适合于给定的ChandraACIS观测，没有公共软件存在来单独模拟粒子诱导背景。目的我们旨在了解ChandraACIS在两种数据模式下获得的粒子诱导背景的时空变化，VFAINT和FAINT。方法使用ACIS在遮蔽天空的存放位置和Chandra深场南方（CDF-S）数据集进行观测。的光谱建模与Al，Si，Ni，和Au和连续组分的仪器线的组合。通过将每个CCD在CHIPY方向上分成32个区域来模拟光谱形状的空间变化。的光谱形状的时间变化进行了建模，使用所有的个人ACIS存放observations.ResultsSimilar空间变化的光谱形状被发现在VFAINT和FAINT数据，这主要是由于不适当的校正的电荷转移效率低下的事件，转换在帧存储区域。光谱硬度比的时间变化最大为10%，这似乎主要是由于太阳活动。我们通过根据总计数率修改光谱硬度来对这种变化进行建模。为了验证这些性质，我们开发了一个工具mkacispback来生成对应于任意天体观测的粒子诱导背景光谱模型。作为一个应用实例，我们使用mkacispback工具产生的背景光谱分析了CDF-S观测中未分辨的宇宙X射线背景。我们发现强度为3.10（2.98-3.21）×10−12erg s−1cm−2deg− 2; 8.35（8.00-8.70）×10− 1-2 erg s− 1 cm − 2 deg − 2，与以前的估计一致或低于以前的估计。结论我们模拟了ChandraACIS-I和S1，S2，和S3 CCD，并开发了一种工具，以生成一个光谱模型的任意天体观测。
ContextIn X-ray observations, estimating the particle-induced background is important, especially for faint and/or diffuse sources. Although software exists to generate total (sky and detector) background data suitable for a givenChandraACIS observation, no public software exists to model the particle-induced background separately.AimsWe aimed to understand the spatial and temporal variations of the particle-induced background ofChandraACIS obtained in the two data modes, VFAINT and FAINT.MethodsObservations performed with ACIS in the stowed position shielded from the sky and theChandraDeep Field South (CDF-S) data sets were used. The spectra were modeled with a combination of the instrumental lines of Al, Si, Ni, and Au and continuum components. The spatial variations of the spectral shapes were modeled by dividing each CCD into 32 regions in the CHIPY direction. The temporal variations of the spectral shapes were modeled using all the individual ACIS-stowed observations.ResultsSimilar spatial variations of the spectral shapes were found in VFAINT and FAINT data, which are mainly due to the inappropriate correction of charge transfer inefficiency for events that convert in the frame-store regions. The temporal variation of the spectral hardness ratio is ∼10% maximum, which seems to be largely due to solar activity. We modeled this variation by modifying the spectral hardnesses according to the total count rate. Incorporating these properties, we developed a tool, mkacispback, to generate the particle-induced background spectral model corresponding to an arbitrary celestial observation. As an example application, we used the background spectrum produced by the mkacispback tool in an analysis of the unresolved cosmic X-ray background in the CDF-S observations. We found intensities of 3.10 (2.98–3.21)×10−12erg s−1cm−2deg−2in the 2–8 keV band and 8.35 (8.00–8.70)×10−12erg s−1cm−2deg−2in the 1–2 keV band, which are consistent with or lower than previous estimates.ConclusionsWe modeled the spatial and temporal variations of the particle-induced background spectra of theChandraACIS-I and the S1, S2, and S3 CCDs, and developed a tool to generate a spectral model for an arbitrary celestial observation.