(a) Date‐sorted PCA spectra of 4U 0115+63 from March 27 to April 8, normalized to the respective best‐fit NPEX models. For the presentation, the results are shifted vertically by a factor of 0.5 for each observation. (b) Same as (a), but the fitting model is NPEX×CYAB2 (March 27 through April 2) or NPEX×CYAB (April 4 and later).