Relations between planetary properties and host stellar abundances. In the top panel, [α/Fe] is computed as the average of individual abundance ratios for α-elements (Mg, Si, Ca, Ti) relative to Fe. The middle panel shows planet radius as a function of [C/O]. Both upper panels are color coded by stellar T_eff. The bottom panel presents [C/Fe] versus [Fe/H], where several metal-poor but carbon-enhanced stars are identified.