Panel a: X-ray luminosity of AT2021ehb in the 0.3–10 keV band. Panels b–e show the evolution of the spectral parameters, where T_in denotes the inner-disk temperature and $R_{\mathrm{in}}^{\ast }$ refers to the apparent inner-disk radius derived from the diskbb model, defined as the true inner-disk radius multiplied by $\sqrt{cosi}$ (where i is the disk inclination), while Γ and f_sc represent the photon index of the comptonized power-law component and the fraction of seed photons scattered into it. In panels b–e, the red star denotes the mean values derived from the spectral fits to the seven XMM-Newton observations, while the blue points are taken from Yao et al. (2022).