A High-Resolution Spectroscopic Survey of Directly Imaged Companion Hosts: III. Characterization of the Cold Imaged Planet Hosts AF Lep A and $\epsilon$ Indi A

Abstract

JWST has enabled the measurement of carbon, oxygen, and sulfur abundances in the atmospheres of directly imaged planets. Interpretation of these abundances from a planet formation standpoint requires the corresponding abundances for the host star. In this work, we present detailed characterizations of the cold imaged planet hosts AF Lep A and $\epsilon$ Indi A using high-resolution Gemini/GHOST spectra. We derive the atmospheric parameters $T_{\mathrm{eff}}$ and $\log g$ using two different approaches, revealing differences in $T_{\mathrm{eff}}$ up to $\sim 260$K. The derived parameters are subsequently incorporated in measurement of 16 elemental abundances (C, O, Na, Mg, Si, S, K, Ca, Sc, Ti, Cr, Mn, Fe, Ni, Zn, Y) and several abundance ratios. Utilizing both the spectral fit and the equivalent width methods, we find solar C/O, C/S and O/S ratios ($<1.5\sigma$) for AF Lep A and $\epsilon$ Indi A. We compare our measured abundances and their ratios with those of the planets AF Lep b and $\epsilon$ Indi Ab, with the elevated abundances for the planets relative to their host stars strongly indicating formation by core-accretion pathways.

16 pages, 4 figures, 8 tables. Accepted to AJ for publication