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Arxiv: Stellar Characterization and Chemical Abundances of Exoplanet Hosting M dwarfs from APOGEE Spectra: Future JWST Targets Published: 5/31/2024 9:03:06 PM Updated: 5/31/2024 9:03:06 PM

Paper abstract: Exoplanets hosting M dwarfs are the best targets to characterize Earth-likeor super-Earth planetary atmospheres with the James Webb Space Telescope(JWST). We determine detailed stellar parameters (T_{\rm eff}, logg, and\xi) and individual abundances of twelve elements for four cool M dwarfshosting exoplanets TOI-1685, GJ 436, GJ 3470, and TOI-2445, scheduled forfuture observations by the JWST. The analysis utilizes high-resolutionnear-infrared spectra from the SDSS-IV APOGEE survey between 1.51-1.69\mu.Based on 1D-LTE plane-parallel models, we find that TOI-2445 is slightlymetal-poor ([Fe/H] = -0.16\pm0.09), while TOI-1685, GJ 436 and GJ 3470 aremore metal-rich ([Fe/H] = 0.06\pm0.18, 0.10\pm0.20 dex, 0.25\pm0.15). Thederived C/O ratios for TOI-2445, TOI-1685, GJ 436, and GJ 3470 are0.526\pm0.027, 0.558\pm0.097, 0.561\pm0.029, and 0.638\pm0.015,respectively. From results for 28 M dwarfs analyzed homogeneously from APOGEEspectra, we find exoplanet-hosting M dwarfs exhibit a C/O abundance ratioapproximately 0.01 to 0.05 higher than those with non-detected exoplanets, atlimits of a statistically significant offset. A linear regression of [Fe/H]\textit{vs.} C/O distribution reveals a noticeable difference in the angularcoefficient between FGK dwarfs (0.27) and M dwarfs (0.13). Assuming ourabundance ratios of Ca/Mg, Si/Mg, Al/Mg, and Fe/Mg, we determine a mass of3.276^{+0.448}_{-0.419}M_{\oplus} for TOI-2445 b, having density(6.793^{+0.005}_{-0.099} g.cm^{-3}) and core mass fraction(0.329_{-0.049}^{+0.028}) very similar to Earth's. We also present an atlasof 113 well-defined spectral lines to analyze M dwarfs in the H-band and acomprehensive evaluation of uncertainties from variations in the atmosphericparameters, signal-to-noise, and pseudo-continuum.