The Long-term Monitoring Results of Insight-HXMT in the First 4 yr Galactic Plane Scanning Survey

Abstract

The first X-ray source catalog of the Insight-HXMT Galactic Plane (∣b∣ < 10°) Scanning Survey (GPSS) is presented based on the data accumulated from 2017 June to 2021 August. The 4 yr limit sensitivities at main energy bands can reach 8.2 × 10−12 erg s−1 cm2 (2−6 keV), 4.21 × 10−11 erg s−1 cm2 (7−40 keV), and 2.78 × 10−11 erg s−1 cm2 (25−100 keV). More than 1300 sources have been monitored at a wide band (1−100 keV), of which 223 sources have a signal-to-noise ratio greater than 5. We combined the GPSS data of Insight-HXMT and MAXI and found it feasible to obtain more complete long-term light curves from their scanning results. The flux variabilities at different energy bands of the 223 bright sources are analyzed based on the excess variances. It is found that the fluxes of X-ray binaries are more active than those of supernova remnants and isolated pulsars. Different types of binaries, e.g., low-mass X-ray binaries (LMXBs), high-mass X-ray binaries (HMXBs), neutron star binaries, and black hole binaries, also distinctively show different regularities. In addition, the relations between the hardness ratio (HR) and excess variances, and HR and source types are analyzed. It is obvious that the HRs of HMXBs tend to be harder than those of LMXBs and HMXBs tend to be more active than those of LMXBs.

Analysis of Bright Source Hardness Ratios in the 4 yr Insight-HXMT Galactic Plane Scanning Survey Catalog

“…The GPSS data reduction and catalog have been presented in detail in Sai et al (2020) and Wang et al (2023); here we only make a brief overview. The Insight-HXMT GPSS utilizes various energy bands, including 1−2, 2−4, 4−6, 2−6, 3−5, 5 −7, 7−40 and 25−100 keV.…”

“…Galactic Plane Scanning Survey (GPSS) is one of its core scientific objectives, occupying 1/3 of its total annual observational time. More than 1300 X-ray sources have been monitored at 1−100 keV after its 4 yr commission (Wang et al 2023). Thanks to the wide band coverage, the HR of the monitored sources can be calculated and analyzed for various combinations of energy bands.…”

“…Thanks to the wide band coverage, the HR of the monitored sources can be calculated and analyzed for various combinations of energy bands. Wang et al (2023) has presented a preliminary summary of the characteristics of the HR of low-mass X-ray binaries (LMXBs) and high-mass X-ray binaries (HMXBs). In this work, we focus on a more detailed analysis of the HR of bright sources in the Insight-HXMT GPSS catalog to provide a more comprehensive understanding of the spectral properties of the monitored sources.…”