Blue curves show the input radiation field used in P08, comprised of three blackbodies with temperature 4 × 10⁴, 8 × 10⁴, and 2 × 10⁶ K. The dashed curve is for L_X = 4 × 10³⁹ erg s^-1 (P08 model M2_X) and the solid curve is for L_X = 8 × 10³⁹ erg s^-1 (P08 model M2_X2). The red curves show the radiation field used in this study, with additional UV-optical contribution (from Lebouteiller et al. 2013) and with an improved X-ray spectrum prescription as compared to P08. The dashed curve is for L_X = 1.4 × 10⁴⁰ erg s^-1 (luminosity inferred from observations) and the solid curve is for L_X = 4 × 10⁴⁰ erg s^-1 (adopted standard). The black diamonds show the unfolded XMM-Newton spectrum (see Sect. 5.3 for more details).