The Isotopic and Elemental Abundances of Planet-Host Star TRAPPIST-1
Abstract
Elemental and isotopic abundances are key tracers of planet formation, stellar evolution, and Galactic chemical evolution. Very low-mass stars are particularly interesting in this regard, because unlike more massive or evolved stars their photospheric abundances retain the star's natal composition. Cool dwarf spectra have historically been challenging to use for measurements of chemical abundances because of the blending of molecular and atomic features. However, recent advances in molecular line lists, atmospheric models, fitting techniques and IR spectrographs have enabled the successful measurement of elemental and isotopic ratios in a few dozen very low-mass stars. Here, we present near-infrared high-resolution spectroscopy of TRAPPIST-1 covering the fundamental and overtone bands of carbon monoxide and its prominent isotopologues. From the joint analysis of the K-band (CFHT/SPIRou) and M-band (Keck/NIRSPEC) spectra, we derive the first stellar C/O ratio and the first carbon and oxygen isotope ratios for this star. We obtain a metallicity of [M/H] = 0.00 ± 0.06, a C/O ratio of 0.60 ± 0.02, 12C/13C = 154+17−16, and 16O/18O = 490+78−64. TRAPPIST-1 has generally solar-like elemental abundances, with a 12C/13C ratio that is higher than the solar value and may be modestly elevated relative to some nearby cool dwarfs at similar metallicity. While C/O is most tightly constrained by the K-band, the isotopic detections are driven by the M-band data.
Versions
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BibTeX
@misc{picos2026isotopic,
title = {{The Isotopic and Elemental Abundances of Planet-Host Star TRAPPIST-1}},
author = {Darío González Picos and Ian J. M. Crossfield and David Coria and Joshua Lothringer and Eric Gaidos and Elisabeth A. C. Mills and Sam de Regt and Donatella Romano and Ignas Snellen},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2608.26097},
eprint = {2608.26097},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.26097},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - The Isotopic and Elemental Abundances of Planet-Host Star TRAPPIST-1
AU - Darío González Picos
AU - Ian J. M. Crossfield
AU - David Coria
AU - Joshua Lothringer
AU - Eric Gaidos
AU - Elisabeth A. C. Mills
AU - Sam de Regt
AU - Donatella Romano
AU - Ignas Snellen
PY - 2026
DA - 2026/10/05
PB - arXiv
DO - 10.48550/arxiv.2608.26097
UR - https://arxiv.org/abs/2608.26097
AB - Elemental and isotopic abundances are key tracers of planet formation, stellar evolution, and Galactic chemical evolution. Very low-mass stars are particularly interesting in this regard, because unlike more massive or evolved stars their photospheric abundances retain the star's natal composition. Cool dwarf spectra have historically been challenging to use for measurements of chemical abundances because of the blending of molecular and atomic features. However, recent advances in molecular line lists, atmospheric models, fitting techniques and IR spectrographs have enabled the successful measurement of elemental and isotopic ratios in a few dozen very low-mass stars. Here, we present near-infrared high-resolution spectroscopy of TRAPPIST-1 covering the fundamental and overtone bands of carbon monoxide and its prominent isotopologues. From the joint analysis of the K-band (CFHT/SPIRou) and M-band (Keck/NIRSPEC) spectra, we derive the first stellar C/O ratio and the first carbon and oxygen isotope ratios for this star. We obtain a metallicity of [M/H] = 0.00 ± 0.06, a C/O ratio of 0.60 ± 0.02, ^12C/^13C = 154^+17_−16, and ^16O/^18O = 490^+78_−64. TRAPPIST-1 has generally solar-like elemental abundances, with a ^12C/^13C ratio that is higher than the solar value and may be modestly elevated relative to some nearby cool dwarfs at similar metallicity. While C/O is most tightly constrained by the K-band, the isotopic detections are driven by the M-band data.
ER -