Evolution of the 10 keV absorption feature energy E_abs1(panel a), its width σ_abs1(panel b), the photon index Γ(panel c), and the reduced χ² of the fits (panel d) as a function of the 1–30 keV flux obtained from the Insight-HXMT data (black points). Red and blue dots show the same parameters derived from two single NuSTAR observations and two combined observations (NuSTAR+Insight-HXMT), respectively. We used the model TBABS × (GAU+CUTOFFPL × GABS) here with the N_H and E_cut fixed at 2.4 × 10²² cm⁻² and 6.66 keV, respectively (see the text).