SIMBAD references

We present a homogeneous spectroscopic analysis of confirmed Kepler's extended mission (K2) exoplanet-hosting stars, comprising 301 targets with high-resolution optical spectra from HIRES and TRES taken from ExoFOP. We derived effective temperatures, surface gravities, and iron and magnesium abundances in local thermodynamic equilibrium by measuring the equivalent widths of Fe I, Fe II, and Mg I lines. Three estimates of stellar masses and radii were obtained via the Stefan-Boltzmann and isochrone methods using the codes PARAM and isochrones. These were used to derive exoplanetary radii reaching internal precisions of 2.5%, 2.6%, and 6.6%, respectively, and the radius gap was consistently detected near 1.9R_⊕. We measured chromospheric activity from the Ca II H and K and Hα lines. Within the low-activity range ($\mathrm{log}R{{\prime} }_{\mathrm{HK}}\lt -4.75$), stellar activity appears to decrease with increasing planetary radius from super-Earths, sub-Neptunes, sub-Saturns, into the Jupiter regime. According to the [Mg/Fe] measurements, most of our K2 planet hosts belong to the Galactic thin disk, but our sample has a population from the thick disk (high-alpha sequence). Most stars show consistent chemodynamical behavior. We find that the [Mg/Fe] ratios are indistinguishable between systems containing large or small exoplanets, as well as single- or multi-exoplanetary systems. Both the [Fe/H] and [Mg/H] distributions reveal that stars hosting large planets are more iron and magnesium enhanced than those having only small planets, further confirming the link between stellar abundances and exoplanetary size, but no significant differences are found between the single- versus multi-exoplanetary systems.