Theoretical atmospheric structure obtained for KELT-20b/MASCARA-2b. Top: HELIOS (dashed orange line) and CLOUDY (in NLTE; dashed cyan line) TP profiles. The solid black line shows the composite TP profile. The horizontal dotted black line indicates the location of the continuum according to the HELIOS model. The horizontal dash-dotted red line gives the location of the CLOUDY’s upper-density limit of 10¹⁵ cm⁻³. The dashed dark green line shows the CLOUDY TP profile computed assuming LTE. The hatched area indicates the Hα line formation region. Bottom: pressure (black; left y-axis) and temperature (red; right y-axis) composite theoretical profiles as a function of the planetary polar radius.