Chemical Abundances of the Bioessential Elements C, O and S, and the Refractory Elements Fe and Ni, in Solar-type Exoplanet-hosting Stars from HARPS North and South

Abstract

We determined atmospheric and evolutionary parameters, along with chemical abundances of C, O, S, Fe, and Ni for 290 solar-type exoplanet hosting stars using high-resolution HARPS-North and HARPS-South spectra, and radii for 373 exoplanets using literature transit depths. We find that stars hosting giant exoplanets (R$_{\text{pl}}>4\ \text{R}_{\oplus}$) show enhanced [X/H] abundances compared to small exoplanet hosts for all elements analyzed. When considering only exoplanets with $P_{\text{orb}}\leq30$ days, there is a statistically significant anti-correlation between host star [Fe/H] and $P_{\text{orb}}$. However, [Fe/H] does not continue to decline as the orbital period increases, but rather rises again for exoplanets with larger orbital periods. Stars hosting only small exoplanets or hosting at least one sub-Saturn show significant differences between the populations of hot and warm exoplanets for all elements. In contrast, stars hosting at least one Jupiter-sized planet show no abundance differences. The host star C/O ratios obtained vary from 0.17 to 0.95, with giant exoplanet hosts exhibiting the lowest median C/O ratios (0.43$^{+0.02}_{-0.03}$), while the 3 -- 4 R$_\oplus$ sub-Neptune hosts in our sample exhibit the highest median C/O ratios (0.55$^{+0.05}_{-0.01}$). Our sample has 199 exoplanets with estimated masses and we find correlations between host star [O/H] and [S/H] and $\log(M_{\text{pl}}/\text{M}_\oplus)$. When segregating the sample into hot and warm exoplanet hosts, these trends are only found for warm exoplanets. Dividing the sample between low- (91 exoplanets) and high-[$\alpha$/Fe] (20 exoplanets) stars, there are 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.