Comparison of the ODR fits to the M dwarfs (large circles) and FGK stars (small gray circles). The median slopes for M dwarfs and FGK stars are shown as red and gray solid lines, respectively, with the associated uncertainties indicated by shaded regions. For [C/H] and [O/H] we show the 1σ and 2σ contours for the synthetic population of FGK stars generated from the compositional correlations found in the Ariel homogeneous stellar sample (R. da Silva et al. 2024).