Abstract:
The well-established planet-metallicity correlation indicates that planets form through the core accretion mechanism, but the influence of other elements besides Fe in this process is still unknown. Thus, expanding stellar abundance studies, particularly for bioessential elements like CHNOPS, is crucial for understanding exoplanet composition and formation. In this study, we determined atmospheric (effective temperature, metallicity and surface gravity) and evolutionary (age, radius and mass) parameters, along with chemical abundances of C, O, S, Fe, and Ni for 291 solar-type exoplanet hosting stars using high-resolution spectra from HARPS South and North, and radii for 373 exoplanets using transit depths from the NASA Exoplanet Archive. We find that stars hosting giant exoplanets (R$_{\text{pl}}>4\ \text{R}_{\oplus}$) show enhanced [X/H] abundances compared to those hosting small exoplanets for all elements analyzed. Considering only exoplanets with $P_{\text{orb}}\leq30$ days, we find a statistically significant anticorrelation between host star [Fe/H] and $P_{\text{orb}}$. However, the metallicity does not continue to decline as the orbital period increases, but rises again for exoplanets having larger orbital periods. Stars hosting small hot or warm exoplanets show significant differences between their abundance distributions for all elements studied here. Host star C/O ratios range from 0.17 to 0.95, with Jupiter hosts having the lowest median value (0.43$^{+0.02}_{-0.03}$), while 3 -- 4 R$_\oplus$ sub-Neptune hosts exhibit the highest median value (0.55$^{+0.05}_{-0.01}$). In our sample, 199 exoplanets have masses determined. We find correlations between host star [O/H] and [S/H] and $\log(M_{\text{pl}}/\text{M}_\oplus)$. We segregated the sample into hot and warm exoplanet hosts and noted that these trends are only found for warms. When dividing the sample between low-[$\alpha$/Fe] (91 exoplanets) and high-[$\alpha$/Fe] (20 exoplanets) stars, we find trends between host star [O/H], [S/H], [Fe/H] and [Ni/H] and $\log(M_{\text{pl}}/\text{M}_\oplus)$ only for the low-[$\alpha$/Fe] sample. These results reveal important links between stellar chemistry and exoplanet properties, offering new constraints on planet formation and valuable context for interpreting the composition of the atmospheres of exoplanets.
