Water content trends in K2-138 and other low-mass multi-planetary systems

Super-Earths and sub-Neptunes have been found simultaneously in multiplanetary systems, suggesting that they are appropriate to study composition formation within the same environment. We perform a homogeneous interior structure analysis of five systems explore compositional trends its relation with planet formation. For K2-138, we present revised masses stellar host chemical abundances improve constraints on planetary interior. conduct line-by-line differential spectroscopic spectra obtain parameters. select or more low-mass planets both mass radius data available. carry out TOI-178, Kepler-11, Kepler-102 Kepler-80 estimate volatile fraction their assuming layer constituted water steam supercritical phases. Our interior-atmosphere model takes into account effects irradiation surface conditions. K2-138 inner an increasing distance from star, while outer approximately constant content. This is similar trend observed TRAPPIST-1 previous model. The system could potentially this trend. In all low be due atmospheric escape higher can result accretion ice-rich material vicinity ice line later inward migration. high core fractions which mantle evaporation, impacts rocklines.