TOI-406 RV datasets

We report the first results of the program, characterising a new 2 planet system around the M-dwarf TOI-406. We analyse TESS and ground-based photometry together with high-precision ESPRESSO and NIRPS/HARPS radial velocities (RVs) to derive the orbital parameters and investigate the internal composition of the 2 planets orbiting TOI-406. TOI-406 hosts two planets with radii and masses of R_c_=1.32R_{Earth}_, M_c_=2.08M_{Earth}_ and R_b_=2.08R_{Earth}_, M_b_=6.57M_{Earth}_, orbiting with periods of 3.3 and 13.2 days, respectively.

The inner planet is consistent with an Earth-like composition, while the external is compatible with multiple internal composition models, including volatile-rich planets without H/He atmospheres. The two planets are located in two distinct regions in the mass-density diagram, supporting the existence of a density gap among small exoplanets around M dwarfs. With an equilibrium temperature of only Teq=368K, TOI-406 b stands up as a particularly interesting target for atmospheric characterisation with JWST in the low-temperature regime.