LEIA in flight performance and variability of flux and spectra of some bright X-ray sources in the Galactic plane

Abstract

We report the results of the first 2-year observations of LEIA in the Galactic plane and demonstrate its excellent performance. We select 34 sources for detailed analysis of their flux and spectral variability. Systematic errors are calculated and the observational performance differences between CMOS15 and CMOS16 are corrected. During the analysis of these sources, excess variance and standard ${\chi }^2$ tests are applied to characterize flux and spectral variability, respectively, and the distributions and their interrelations are analyzed. A variable flux is observed in most sources, with a more significant difference in flux variability observed closer to the Galactic Center. Two methods are employed to characterize spectral variability: fluctuations in the Hardness Ratio (HR) derived from count rates in the high-to-low energy bands, and variability in the photon index (Γ) obtained from spectral fitting. The results from both methods are broadly consistent. The findings suggest that the spectra of most XRBs are variable. Statistical analysis of flux and spectral variability for the sample sources reveals no significant correlation between the two. As a result, the first 2-year XRBs catalog of LEIA in the Galactic plane is presented. At the same time, the analysis of the sources indicate that the observation data of LEIA are usable and valuable, fulfilling its mission as the pathfinder of lobster-eye Wide-field X-ray Telescope onboard the Einstein Probe mission.