X-ray spectra of PG 1448+273 with the optical/UV data from the OM. Left panel: the lines of different colour represent the best-fitting warm corona models obtained by fitting the corresponding colour X-ray data under the condition of a = 0 and M_BH = 9 × 10⁶ M_⊙. These best-fitting models are extrapolated to the optical/UV band to compare the observed optical/UV data, and the observed optical/UV fluxes significantly exceed the extrapolated value of the models. Right panel: the lines of different colours represent the best-fitting warm coronal model obtained by simultaneously fitting the corresponding colour X-ray and optical/UV data under the condition of a = 0 and a free black hole mass.