Alternative agnsed  + pexmon model configurations for the HF data set. The model variants are defined as in Fig. D1. For the model variant with |$kT_{e,\mathrm{hot}}=50$| keV, the cool outer disc component is minimized in the fit, yielding very similar overall results to the ‘no cool disc’ model presented in the main text (Section 4.2). We note that the ‘Full Model’ spectra in these figures (black curves) are normalized relative to the XMM–Newton spectrum. Because the NuSTAR combined spectrum in the HF data set has a |$\sim 20$| per cent higher overall flux level compared to the XMM–Newton spectrum, an offset is visible between NuSTAR and XMM–Newton. As discussed in Section 3.3, we account for flux offsets via multiplicative scaling constants in our modelling.