Background model for the high-energy telescope of Insight-HXMT
Abstract
Accurate background estimation is essential for spectral and temporal analysis in astrophysics. In this work, we construct the in-orbit background model for the High-Energy Telescope (HE) of the Hard X-ray Modulation Telescope (dubbed as Insight-HXMT). Based on the two-year blank sky observations of Insight-HXMT/HE, we first investigate the basic properties of the background and find that both the background spectral shape and intensity have long-term evolution at different geographical sites. The entire earth globe is then divided into small grids, each with a typical area of 5 × 5 square degrees in geographical coordinate system. For each grid, an empirical function is used to describe the long-term evolution of each channel of the background spectrum; the intensity of the background can be variable and a modification factor is introduced to account for this variability by measuring the contemporary flux of the blind detector. For a given pointing observation, the background model is accomplished by integrating over the grids that are passed by the track of the satellite in each orbit. Such a background model is tested with both the blank sky observations and campaigns for observations of a series of celestial sources. The results show an average systematic error of 1.5% for the background energy spectrum (26- 100 keV) under a typical exposure of 8 ks, and < 3% for background light curve estimation (30- 150 keV). Therefore, the background model introduced in this paper is included in the Insight-HXMT software as a standard part specialized for both spectral and temporal analyses.
- Publication:
-
Journal of High Energy Astrophysics
- Pub Date:
- August 2020
- DOI:
- arXiv:
- arXiv:2005.01661
- Bibcode:
- 2020JHEAp..27...14L
- Keywords:
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- Instrumentation: detectors;
- Space vehicles: instruments;
- Methods: data analysis;
- X-rays: general;
- Astrophysics - Instrumentation and Methods for Astrophysics;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 27 pages, 16 figures, accepted by Journal of High Energy Astrophysics