The Composition of M-dwarf Exoplanet Hosts: Atmospheric Parameters and O, Mg, Si, and Fe Abundances from IR Spectroscopy
Abstract
Determining M-dwarf abundances is an important step to discerning the chemical evolution of the Milky Way and characterizing exoplanetary systems, especially since these objects commonly host small exoplanets. However, a dearth of M-dwarf abundance measurements exist compared to Sun-like stars, partially due to their complicated optical spectra dominated by molecular absorption lines and low luminosities. To overcome these issues, we have obtained high resolution H-band spectra of 40 planet-hosting M-dwarf stars and 2 M-dwarfs in wide binaries with FGK primaries with IGRINS on Gemini South and on the McDonald Observatory 2.7m telescope, and NIRSPEC on Keck. Abundances were derived by comparing each observed spectrum to synthetic spectral grids generated with MOOG and MARCS atmospheric models. Effective temperatures were derived using OH and H2O lines and [Fe/H] from Fe I and FeH lines. Both Mg and Si abundances were determined using atomic features. Overall, we find that our abundances are broadly consistent with previous literature M-dwarf abundances. We complemented our abundances analysis with UVW velocities and Milky Way stellar population membership probabilities and identified 2 potential thick disk stars from our kinematic and chemical analysis: GJ 1252 and L181-1 which was a previously known thick disk star. Kinematic stellar population probabilities and a low [Fe/H] abundance makes Kepler 42 a likely thick disk star, although uncertain Mg and Si abundances make classification difficult. Lastly, we have determined Si/Mg and Fe/Mg molar ratios for M-dwarf exoplanet hosts and find the abundance distributions leads to exoplanet core-mass fractions between 20 - 40%.
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BibTeX
@misc{maas2026composition,
title = {{The Composition of M-dwarf Exoplanet Hosts: Atmospheric Parameters and O, Mg, Si, and Fe Abundances from IR Spectroscopy}},
author = {Zachary G Maas and Natalie R. Hinkel and Gregory N. Mace and Cayman T. Unterborn and Catherine Pilachowski and Christopher Sneden and Isabella Flores and Joseph G. Schulze},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.07037},
eprint = {2611.07037},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.07037},
}
RIS
TY - UNPB
TI - The Composition of M-dwarf Exoplanet Hosts: Atmospheric Parameters and O, Mg, Si, and Fe Abundances from IR Spectroscopy
AU - Zachary G Maas
AU - Natalie R. Hinkel
AU - Gregory N. Mace
AU - Cayman T. Unterborn
AU - Catherine Pilachowski
AU - Christopher Sneden
AU - Isabella Flores
AU - Joseph G. Schulze
PY - 2026
DA - 2026/11/04
PB - arXiv
DO - 10.48550/arxiv.2611.07037
UR - https://arxiv.org/abs/2611.07037
AB - Determining M-dwarf abundances is an important step to discerning the chemical evolution of the Milky Way and characterizing exoplanetary systems, especially since these objects commonly host small exoplanets. However, a dearth of M-dwarf abundance measurements exist compared to Sun-like stars, partially due to their complicated optical spectra dominated by molecular absorption lines and low luminosities. To overcome these issues, we have obtained high resolution H-band spectra of 40 planet-hosting M-dwarf stars and 2 M-dwarfs in wide binaries with FGK primaries with IGRINS on Gemini South and on the McDonald Observatory 2.7m telescope, and NIRSPEC on Keck. Abundances were derived by comparing each observed spectrum to synthetic spectral grids generated with MOOG and MARCS atmospheric models. Effective temperatures were derived using OH and H_2O lines and [Fe/H] from Fe I and FeH lines. Both Mg and Si abundances were determined using atomic features. Overall, we find that our abundances are broadly consistent with previous literature M-dwarf abundances. We complemented our abundances analysis with UVW velocities and Milky Way stellar population membership probabilities and identified 2 potential thick disk stars from our kinematic and chemical analysis: GJ 1252 and L181-1 which was a previously known thick disk star. Kinematic stellar population probabilities and a low [Fe/H] abundance makes Kepler 42 a likely thick disk star, although uncertain Mg and Si abundances make classification difficult. Lastly, we have determined Si/Mg and Fe/Mg molar ratios for M-dwarf exoplanet hosts and find the abundance distributions leads to exoplanet core-mass fractions between 20 - 40%.
ER -