Radial midplane temperature profiles for the L1527 disk and inner envelope. Top panel: comparison between the temperature profile from the T13 model and power laws with different exponents (q). Middle and bottom panels: power law profiles derived from ¹³CO (orange lines) and C¹⁸O observations(blue lines) assuming q = 0.5 and q = 0.35, respectively. Solid lines are derived from a redshifted channel, dashed lines from a blueshifted channel. The measured values are indicated by filled circles. The orange shaded area shows the 1σ uncertainty on the solid orange line (¹³CO from redshifted channel). The gray shaded area marks the temperature range for which CO is expected to be frozen out (i.e., below 20 K). The vertical dash-dotted line marks a disk radius of 74 au as determined by A17, and the dotted line a disk radius of 125 au derived by T13.