Rotational temperatures derived from fitting the MB (2.59–2.76 μm) and HB (2.774–2.91 μm) spectral regions. (A) as a function of distance to nucleus centre ρ, with a colour-coding according to heliocentric distance; only LOSs with a position angle with respect to the comet-Sun line PA_LOS < 45° were considered; results from S3-S4 and H1-H2 spectra are included; the fitted curves are (dashed red line for r_h < 1.4 au), and (dashed green line for 1.4 au < r_h < 1.8 au). (B) Ratio as a function of the attenuation factor f_atten with symbol colours according to .