HEX-P simulation with an exposure time of 500 ks. The simulated spectra were generated using the RHBDP model (with the parameters obtained from the best fit of the low-flux Obs. ID 0864550201). The spectra were then fitted with the disc blackbody + comptonisation components (RHDCom model, χ²/d.o.f. = 485/356). The disc blackbody and the comptonisation components are represented in orange and blue, respectively. The residuals show that a third component is necessary to describe the simulated spectra above 8 keV.