In-flight calibration of the Insight-Hard X-ray Modulation Telescope

Abstract

We present the calibration of the Insight-Hard X-ray Modulation Telescope (Insight-HXMT) X-ray satellite, which can be used to perform timing and spectral studies of bright X-ray sources. Insight-HXMT carries three main payloads onboard: the High Energy X-ray telescope (HE), the Medium Energy X-ray telescope (ME) and the low Energy X-ray telescope (LE). In orbit, the radioactive sources, activated lines, the fluorescence lines and celestial sources are used to calibrate the energy scale and energy resolution of the payloads. The Crab nebular is adopted as the primary effective area calibrator and empirical functions are constructed to modify the simulated effective areas of the three payloads respectively. The systematic errors of HE, compared to the model of the Crab nebular, are less than 2% in 28-120 keV and 2%-10% above 120 keV. The systematic errors of ME are less than 1.5% in 10-35 keV. The systematic errors of LE are less than 1% in 1-7 keV except the Si K-edge (1.839 keV, up to 1.5%) and less than 2% in 7-10 keV.

Comparison of simulated backgrounds with in-orbit observations for HE, ME, and LE onboard Insight-HXMT

“…To investigate the rapid increase of HE back- around 57 keV, which originates from HE tantalum collimators, are clearly seen. All of these line structures in background spectrum could be used in the in-orbit calibration of HE (Li et al 2020). After a long term operation in space, the background rate of HE increases, especially at the energy of ∼67 keV, as presented in Fig.…”