Comparison of simulated backgrounds with in-orbit observations for HE, ME, and LE onboard Insight-HXMT
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ORIGINAL ARTICLE
Comparison of simulated backgrounds with in-orbit observations for HE, ME, and LE onboard Insight-HXMT Juan Zhang1 · Xiaobo Li1 · Mingyu Ge1 · Haisheng Zhao1 · Youli Tuo1,2 · Fei Xie3 · Gang Li1 · Shijie Zheng1 · Jianyin Nie1 · Liming Song1 · Aimei Zhang1 · Yanji Yang1 · Yong Chen1
Received: 7 April 2020 / Accepted: 17 September 2020 / Published online: 30 September 2020 © Springer Nature B.V. 2020
Abstract Insight-HXMT, the first X-ray astronomical satellite in China, aims to reveal new sources in the Galaxy and to study fundamental physics of X-ray binaries from 1 to 250 keV. It has three collimated telescopes, the High Energy X-ray telescope (HE), the Medium Energy X-ray telescope (ME), and the Low Energy X-ray telescope (LE). Before the launch, in-orbit backgrounds of these three telescopes had been estimated through Geant4 simulation, in order to investigate the instrument performance and the achievement of scientific goals. In this work, these simulated backgrounds are compared with in-orbit observations. Good agreements are shown for all three telescopes. For HE, (1) the deviation of the simulated background rate after two years of operation in space is ∼ 5% from the observation; (2) the total background spectrum and the relative abundance of the ∼67 keV line show long-term increases both in simulations and observations. For ME, (1) the deviation of simulated background rate is within ∼ 15% from the observation, and (2) there are no obvious long-term increase features in the background spectra of simulations and observations. For LE, the background level given by simulations is also consistent with observations. The consistencies of these comparisons validate that the Insight-HXMT mass model, i.e., space environment components and models adopted, physics processes selected, and detector constructions built, is reasonable. However, the line features at ∼7.5 and 8.0 keV, which are obvious in the observed spectra of LE, are not evident in
B J. Zhang
[email protected]
1
Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
2
University of Chinese Academy of Sciences, Beijing, China
3
INAF-IAPS, via del Fosso del Cavaliere 100, 00133 Roma, Italy
simulations. This might result from uncertainties in the LE constructions. Keywords Insight-HXMT · Geant4 simulation · Background observation
1 Introduction Due to atmospheric absorption, X-ray radiation of astrophysical sources needs to be detected in space. However, satellite-borne detectors suffer from enormous space radiation including cosmic rays, diffuse X-rays, solar flares, the albedo of the Earth, charged particles trapped in the radiation belts, and so on. Besides causing damage to sensitive detectors, the space radiation also results in background events during scientific observations of target sources. The space-induced background varies with each instrument, according to the detector type and operation orbit (e.g., Jahoda et al. 2006; Rothschild et al. 199
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