Elemental Abundances of Planet-Host Cool Dwarfs: Clues on Planet Formation and Evolution

Hejazi, Neda; Crossfield, Ian J. M.; Souto, Diogo; Pavlenko, Yakiv; Nordlander, Thomas; Cunha, Katia; Marfil, Emilio; Smith, Verne V.; Coria, David R.
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American Astronomical Society Meeting Abstracts

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Since a large fraction of stars harbor at least one planet, the formation of planets around newly forming stars appears to be a common phenomenon. Planet cores are believed to grow by accreting materials from a protoplanetary disk spinning around its host star. This host star has a strong impact on the properties of the protoplanetary disk, and inversely, the accretion of planetary material into the star may change the stellar elemental abundances. In addition, the relative enrichment of refractory and volatile materials as well as some pivotal abundance ratios such as C/O between planet and its host star depends on whether the planet is formed interior or exterior to the ice line, and whether the planet has undergone a kind of migration. The comparison between the chemical properties of planets and those of their parent stars could therefore provide critical information about the formation and evolutionary pathways of planetary systems. While JWST is now measuring the atmospheric chemical composition of planets with unparalleled accuracy, the elemental abundance measurement of cool dwarfs, whose orbiting planets are most sensitive to widely used exoplanet detection techniques, has still remained challenging. Due to the dominant molecular lines, the methods such as equivalent width analysis, that are readily used to obtain chemical abundances of hotter stars, do not apply to the spectra of cool dwarfs. We thus present an iterative synthetic model fitting using MARCS model atmospheres and the spectral synthesis code TurboSpectrum to determine the elemental abundances of JWST cool host stars (3100 < Teff < 4700) whose planetary atmospheric compositions will also be measured. We employ the high-resolution (R=45,000), NIR spectra observed by Gemini-S/IGRINS to measure the abundances of key chemical elements: C, O, Na, Mg, Al, K, Ca, Ti, and Fe in all stars, as well as N, Si, V, Cr, Mn, and Ni in warmer stars. Owing to the growing number of stars with confirmed planet(s), we are aiming to automate our fitting pipeline, which could be a promising method to measure the composition of stars hosting planets that will be targeted by future surveys such as PLATO and Ariel missions.