Expanding the Volatile Abundance Inventory for High-Priority K-Dwarf JWST Exoplanet Systems
Auteurs : David R. Coria, Neda Hejazi, Ian J. M. Crossfield, Ismael Mireles, Casey L. Brinkman, Jared R. Kolecki, Emilio Marfil, Thomas Nordlander, Lauren M. Weiss, Diana Dragomir
Résumé scientifique
There are exceedingly few chemical abundance measurements available in the literature for K dwarf stars, especially for those with T$_{eff} <$ 4700 K due to an incompatibility of traditional analyses with their molecular-line-ridden optical spectra. To address the need for K dwarf abundance constraints, we present an elemental ([C/H], [O/H]) and isotopic ($^{12}$C/$^{13}$C, $^{16}$O/$^{18}$O) abundance analysis for six K dwarf exoplanet host stars: K2-141, NGTS-10, WASP-43, WASP-69, WASP-80, and HATS-72. Each system hosts an exoplanet targeted by JWST characterization efforts, making host star abundances especially critical as baseline references. Using MARCS model atmospheres, the TurboSpectrum spectral synthesis code, and near-infrared IGRINS spectra, we derive novel [C/H] and [O/H] abundance ratios for these high-priority K dwarf host stars. We further investigate prospects for determining $^{12}$C/$^{13}$C and $^{16}$O/$^{18}$O ratios using $^{13}$C$^{16}$O and $^{12}$C$^{18}$O lines from the 2.3 micron CO bandhead. The observed spectra are too noisy to measure $^{16}$O/$^{18}$O ratios for the sample, but we do find sub-solar $^{12}$C/$^{13}$C ratios for five out of six targets. We also derive uniform gyrochronological ages for each host star to compare with galactic chemical evolution models and identify underlying abundance-age trends. NIR H+K band spectroscopy provides an alternative to optical, atomic line-derived carbon and oxygen abundances for cool dwarf stars. The growing catalog of precise host star elemental and isotopic abundances complements ongoing observations of their companions and provides a baseline for understanding their chemical composition, origin, and evolution.
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