Stellar Characterization and Chemical Abundances of Exoplanet Hosting M dwarfs from APOGEE Spectra: Future JWST Targets

By Keith Cowing
Status Report
June 4, 2024
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Stellar Characterization and Chemical Abundances of Exoplanet Hosting M dwarfs from APOGEE Spectra: Future JWST Targets
The [Fe/H] versus C/O distribution for this work sample, as well as other M dwarfs studied by Souto et al. (2017), Souto et al. (2018), Souto et al. (2020). The orange circles represent the results for the four JWST targets studied here; Results for M dwarfs from our previous studies (all based on the same methodology as here) are also shown: orange triangles are M dwarfs with exoplanets detected, while the gray squares are M dwarfs without exoplanets detected so far. We also present results for FGK dwarfs from Nissen (2013) (green triangles; all with detected exoplanets), Teske et al. (2014) with (light blue diamonds) detected exoplanets, and Delgado Mena et al. (2021) with (pink circles), and without detected exoplanets (yellow cross). Additionally, four curves represent the linear regressions of the [Fe/H] vs. C/O distribution for M dwarfs with planet detected (solid orange line), M dwarfs without planet detected (solid gray line), FGK dwarfs with detected planets (dashed orange line), and FGK dwarfs without detected planets (dashed gray line). — astro-ph.SR

Exoplanets hosting M dwarfs are the best targets to characterize Earth-like or super-Earth planetary atmospheres with the James Webb Space Telescope (JWST). We determine detailed stellar parameters (Teff, logg, and ξ) and individual abundances of twelve elements for four cool M dwarfs hosting exoplanets TOI-1685, GJ 436, GJ 3470, and TOI-2445, scheduled for future observations by the JWST.

The analysis utilizes high-resolution near-infrared spectra from the SDSS-IV APOGEE survey between 1.51-1.69μ. Based on 1D-LTE plane-parallel models, we find that TOI-2445 is slightly metal-poor ([Fe/H] = -0.16±0.09), while TOI-1685, GJ 436 and GJ 3470 are more metal-rich ([Fe/H] = 0.06±0.18, 0.10±0.20 dex, 0.25±0.15). The derived C/O ratios for TOI-2445, TOI-1685, GJ 436, and GJ 3470 are 0.526±0.027, 0.558±0.097, 0.561±0.029, and 0.638±0.015, respectively.

From results for 28 M dwarfs analyzed homogeneously from APOGEE spectra, we find exoplanet-hosting M dwarfs exhibit a C/O abundance ratio approximately 0.01 to 0.05 higher than those with non-detected exoplanets, at limits of a statistically significant offset. A linear regression of [Fe/H] \textit{vs.} C/O distribution reveals a noticeable difference in the angular coefficient between FGK dwarfs (0.27) and M dwarfs (0.13). Assuming our abundance ratios of Ca/Mg, Si/Mg, Al/Mg, and Fe/Mg, we determine a mass of 3.276+0.448−0.419M for TOI-2445 b, having density (6.793+0.005−0.099 this http URL−3) and core mass fraction (0.329+0.028−0.049) very similar to Earth’s.

We also present an atlas of 113 well-defined spectral lines to analyze M dwarfs in the H-band and a comprehensive evaluation of uncertainties from variations in the atmospheric parameters, signal-to-noise, and pseudo-continuum.

Edypo Melo, Diogo Souto, Katia Cunha, Verne V. Smith, Fábio Wanderley, Vinicius Grilo, Deusalete Camara, Kely Murta, Neda Hejazi, Ian J.M. Crossfield, Johanna Teske, Rafael Luque, Michael Zhang, Jacob Bean

Comments: 32 pages, 3 figures. Accepted to the Astrophysical Journal (ApJ)
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2406.00111 [astro-ph.SR] (or arXiv:2406.00111v1 [astro-ph.SR] for this version)
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Submission history
From: Édypo Ribeiro De Melo
[v1] Fri, 31 May 2024 18:03:06 UTC (254 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻