2025A&A...695A.237R

Context. One of the goals of the ESPRESSO guaranteed time observations (GTOs) at the ESO 8.2 m telescope is to follow up on candidate planets from transit surveys such as the TESS mission. High-precision radial velocities are required to characterize small exoplanets.
Aims. We intend to confirm the existence of a transiting super-Earth around the bright (V=9.74) K0-type star TOI-512 (TIC 119292328) and provide a characterization.
Methods. Combining photometric data from TESS and 37 high-resolution spectroscopic observations from ESPRESSO in a joint Markov chain Monte Carlo analysis, we determined the planetary parameters of TOI-512b and characterized its internal structure.
Results. We find that TOI-512b is a super-Earth, with a radius of 1.54 ± 0.10 R_⊕ and mass of 3.57_–0.55^+0.53 M_⊕, on a 7.19_{–6.1·10–5}^+7.10-5 day orbit. This corresponds to a bulk density of 5.62_–1.28^+1.59 g cm^–3. Our interior structure analysis presents a small inner core representing 0.13_–0.11^+0.13 of the solid mass fraction for the planet, surrounded by a mantle with a mass fraction of 0.69_–0.22^+0.20, and an upper limit of the water layer of 0.16. The gas mass below 10^–8.93 indicates a very small amount of gas on the planet. We find no evidence of the second candidate found by the TESS pipeline, TOI-512.02, neither in TESS photometry, nor in the ESPRESSO radial velocities. The low stellar activity makes it an interesting transmission spectroscopy candidate for future-generation instruments.