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

TL;DR

This paper presents the first X-ray source catalog from Insight-HXMT's 4-year Galactic Plane survey, analyzing source variability, combining data with MAXI, and exploring source properties and classifications.

Contribution

It provides the first comprehensive catalog of X-ray sources from Insight-HXMT's Galactic Plane survey and analyzes long-term variability and source classifications.

Findings

Over 1300 sources monitored in 1-100 keV band.

Flux variability higher in X-ray binaries than supernova remnants.

HMXBs tend to be harder and more active than LMXBs.

Abstract

The first X-ray source catalog of Insight-HXMT Galactic Plane (|b|<10deg) Scanning Survey (GPSS) is presented based on the data accumulated from June 2017 to August 2021. The 4 yr limit sensitivities at main energy bands can reach 8.2x10^(-12) erg/s/cm^2} (2-6 keV), 4.21x10^(-11) erg/s/cm^2 (7-40 keV) and 2.78x10^(-11) erg/s/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 is 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.