Three Super-Earths and a Possible Water World from TESS and ESPRESSO

Since 2018, the ESPRESSO spectrograph at the VLT has been hunting for planets in the southern skies via the radial velocity (RV) method. One of its goals is to follow up on candidate planets from transit surveys such as the TESS mission, with a particular focus on small planets for which ESPRESSO's RV precision is vital. We aim to confirm and characterise, in detail, three super-Earth candidate transiting planets from TESS using precise RVs from ESPRESSO. We analysed photometry from TESS and ground-based facilities, high-resolution imaging, and RVs from ESPRESSO, HARPS, and HIRES, to confirm and characterise three new planets: TOI-260 b, transiting a late K dwarf, and TOI-286 b and c, orbiting an early K dwarf. We also updated the parameters for the known super-Earth TOI-134 b (L 168-9 b), which is hosted by an M dwarf. TOI-260 b has a d period, $4.23 M_ oplus $ mass, and $1.71 R_ oplus $ radius. For TOI-286 b we find a d period, $4.53 M_ oplus $ mass, and $1.42 R_ oplus $ radius; for TOI-286 c, we find a d period, $3.72 M_ oplus $ mass, and $1.88 R_ oplus $ radius. For TOI-134 b we obtain a d period, $4.07 M_ oplus $ mass, and $1.63 R_ oplus $ radius. Circular models are preferred for all the planets, although for TOI-260 b the eccentricity is not well constrained. We computed bulk densities and placed the planets in the context of composition models. TOI-260 b lies within the radius valley, and is most likely a rocky planet. However, the uncertainty on the eccentricity and thus on the mass renders its composition hard to determine. TOI-286 b and c span the radius valley, with TOI-286 b lying below it and having a likely rocky composition, while TOI-286 c is within the valley, close to the upper border, and probably has a significant water fraction. With our updated parameters for TOI-134 b, we obtain a lower density than previous findings, giving a rocky or Earth-like composition.