Temperature-pressure profiles obtained employing HELIOS (orange dashed line) and Cloudy (in NLTE; cyan dashed line). The black solid line shows the composite TP profile, while the horizontal black dashed lines indicate the location within which the HELIOS and Cloudy TP profiles have been merged. The horizontal dark green dash-dotted line indicates the location of Cloudy’s upper density limit (10¹⁵ cm⁻³). The magenta dash-dotted line shows the TP profile computed with PHOENIX (Lothringer & Barman 2020). The hatched area indicates the main line formation region (Turner et al. 2020; Fossati et al. 2020).