Top panel: Disc luminosity in the 0.3–2.0 keV band versus time as derived from our spectral analysis assuming no disc inclination changes between epochs (Table D.1). The square, diamond, and triangle symbols represent the XMM-Newton, Swift, and Chandra observations, respectively. Upper limits from the ROSAT and eROSITA surveys are also shown (time-shifted for plotting clarity; Voges et al. 1999; Tubín-Arenas et al. 2024). Bottom panel: Fitted disc mass accretion rate ṁ for each epoch, normalised by the Eddington-limited accretion rate (computed assuming a black hole mass of 5.7 × 10⁴ M_⊙). The dashed line indicates trans-Eddington accretion.