Two interpretations of the steeper slope of the WLQ continuum. a) At the bottom of the panel, the WLQ composite spectrum (red) is compared with the slightly smoothed SDSS quasar composite spectrum (solid blue) fitted by a MTBB model with temperature parameter T^∗ = 8 × 10⁴ K (dotted blue). The thick black curve above is a modified version of the SDSS quasar composite with a hotter continuum fitted to the MTBB model for T^∗ = 10⁵ K and compared with the WLQ composite spectrum (red) that is normalised to match the former at the right hand side. b) as a), but the modification of the SDSS quasar composite spectrum consists of an additional power-law component instead of a hotter continuum. Vertical lines: continuum windows.