Spectral fitting and residual analysis for NICER and NuSTAR observations. Panels a and b: Spectral fit using the model TBabs × (4 × gabs)×edge × thcomp × comptt. The black lines represent the NICER data in the energy range of 1−10 keV. The red and green lines correspond to the NuSTAR data from the FPMA and FPMB mirrors, respectively, covering the energy range of 4−25 keV. Panels c and d: Residuals of the spectral fit without the gabs and edge components. The black lines indicate the NICER data, and the red and green lines represent the FPMA and FPMB data from NuSTAR. The depicted energy ranges are 2−10 keV for NICER and 10−25 keV for NuSTAR.