1Darío González Picos, 2Ian J. M. Crossfield, 3David Coria, 4Joshua Lothringer, 5Eric Gaidos, 2Elisabeth A. C. Mills, 1Sam de Regt, 6Donatella Romano, 1Ignas Snellen
The Astrophysical Journal, 1010, 22
Open Source Link to Article [DOI: 10.3847/1538-4357/ae9bbc]
1Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA, Leiden, The Netherlands
2Department of Physics and Astronomy, University of Kansas, Lawrence, KS, USA
3Department of Physics and Astronomy, University of New Mexico, Albuquerque, NM, USA
4Space Telescope Science Institute, Baltimore, MD, USA
5Department of Earth Sciences, University of Hawai’i at Mānoa, Honolulu, HI, USA
6INAF-Osservatorio di Astrofisica e Scienza dello Spazio, Bologna, Italy
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-IR 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 , a C/O ratio of , , and . TRAPPIST-1 has generally solar-like elemental abundances, with a 12C/13C 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.
