HD 23472: a multi-planetary system with three super-Earths and two potential super-Mercuries,

We report the characterisation of a multi-planetary system composed five exoplanets orbiting K-dwarf HD~23472 (TOI-174). In addition to two super-Earths that were previously confirmed, we confirm and characterise three Earth-size planets in using ESPRESSO radial velocity observations. The this compact have periods $P_d \sim 3.98\,$, $P_e 7.90\,$, $P_f 12.16\,$, $P_b 17.67,\,$ $P_c 29.80\,$days radii $R_d 0.75\,$ , $R_e 0.82,$, $R_f 1.13\,$, $R_b 2.01,\,$ and, $R_c 1.85\,$ \REarth. Because its small size, proximity planet d's transit, close resonance with d, e was only recently found. planetary masses estimated be $M_d =0.54\pm0.22$, $M_e =0.76\pm0.30$, $M_f =0.64_{-0.39}^{+0.46}$, $M_b = 8.42_{-0.84}^{+0.83}$, $M_c 3.37_{-0.87}^{+0.92}$ \MEarth. These are among lightest planets, measured method, demonstrating very high precision spectrograph. composition system's found their gas water mass fractions increase stellar distance, suggesting shaped by irradiation. density inner ($\rho_d 7.5_{-3.1}^{+3.9}$ $\rho_e 7.5_{-3.0}^{+3.9}\, \mathrm{g.cm^{-3}}$) indicates they likely super-Mercuries. This is supported modelling internal structures which also suggests outermost significant or content If existence super-Mercuries will one known feature super-Mercuries, making it an excellent testing bed for theories formation. (Abridged)