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

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 cm 2 (2−6 keV), 4.21 × 10 −11 erg s −1 cm 2 (7−40 keV), and 2.78 × 10 −11 erg s −1 cm 2 (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.