直接成像伴星宿主的高分辨率光谱巡天：III. 冷成像行星宿主AF Lep A与ε Indi A的表征
A High-Resolution Spectroscopic Survey of Directly Imaged Companion Hosts: III. Characterization of the Cold Imaged Planet Hosts AF Lep A and $ε$ Indi A
AI总结：
本研究利用高分辨率Gemini/GHOST光谱表征冷成像行星宿主AF Lep A与ε Indi A，测得其太阳型丰度比，行星丰度相对宿主升高，支持行星核吸积形成理论。
AI中文摘要：
詹姆斯·韦布空间望远镜（JWST）已实现对直接成像行星大气中碳、氧、硫丰度的测量。从行星形成角度解读这些丰度，需要对应宿主恒星的丰度数据。本研究利用高分辨率的双子座天文台GHOST光谱，对冷成像行星宿主AF Lep A与ε Indi A开展详细表征：采用两种不同方法推导大气参数有效温度（$T_{\rm eff}$）与表面重力对数（$\rm log{g}$），发现二者有效温度差异最高达约260开尔文；将推导得到的参数用于测量16种元素（碳、氧、钠、镁、硅、硫、钾、钙、钪、钛、铬、锰、铁、镍、锌、钇）的丰度及多种丰度比；结合光谱拟合与等值宽度两种方法，发现AF Lep A与ε Indi A的碳氧、碳硫、氧硫丰度比均为太阳型（偏差小于1.5倍标准差）；将测得的丰度及其比值与行星AF Lep b、ε Indi Ab对比，发现行星丰度相对宿主恒星升高，强烈表明其形成于核吸积路径。
英文摘要：
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 $ε$ Indi A using high-resolution Gemini/GHOST spectra. We derive the atmospheric parameters $T_{\rm eff}$ and $\log{g}$ using two different approaches, revealing differences in $T_{\rm eff}$ up to $\sim260\,$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 ($<1.5σ$) for AF Lep A and $ε$ Indi A. We compare our measured abundances and their ratios with those of the planets AF Lep b and $ε$ Indi Ab, with the elevated abundances for the planets relative to their host stars strongly indicating formation by core-accretion pathways.
