Comprehensive High-resolution Chemical Spectroscopy of Barnard's Star with SPIRou

Farbod Jahandar; René Doyon; Étienne Artigau; Neil J. Cook; Charles Cadieux; David Lafrenière; Thierry Forveille; Jean-François Donati; Pascal Fouqué; Andrés Carmona; Ryan Cloutier; Paul Cristofari; Eric Gaidos; João Gomes da Silva; Lison Malo; Eder Martioli; J. -D. do Nascimento Jr.; Stefan Pelletier; Thomas Vandal; Kim Venn

arXiv · 2310.12125

Comprehensive High-resolution Chemical Spectroscopy of Barnard's Star with SPIRou

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Abstract

Determination of fundamental parameters of stars impacts all fields of astrophysics, from galaxy evolution to constraining the internal structure of exoplanets. This paper presents a detailed spectroscopic analysis of Barnard's star that compares an exceptionally high-quality (an average signal-to-noise ratio of $\sim$1000 in the entire domain), high-resolution NIR spectrum taken with CFHT/SPIRou to PHOENIX-ACES stellar atmosphere models. The observed spectrum shows thousands of lines not identified in the models with a similar large number of lines present in the model but not in the observed data. We also identify several other caveats such as continuum mismatch, unresolved contamination and spectral lines significantly shifted from their expected wavelengths, all of these can be a source of bias for abundance determination. Out of $>10^4$ observed lines in the NIR that could be used for chemical spectroscopy, we identify a short list of a few hundred lines that are reliable. We present a novel method for determining the effective temperature and overall metallicity of slowly-rotating M dwarfs that uses several groups of lines as opposed to bulk spectral fitting methods. With this method, we infer $T_{eff}$ = 3231 $\pm$ 21 K for Barnard's star, consistent with the value of 3238 $\pm$ 11 K inferred from the interferometric method. We also provide abundance measurements of 15 different elements for Barnard's star, including the abundances of four elements (K, O, Y, Th) never reported before for this star. This work emphasizes the need to improve current atmosphere models to fully exploit the NIR domain for chemical spectroscopy analysis.

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Farbod Jahandar, René Doyon, Étienne Artigau, Neil J. Cook, Charles Cadieux, David Lafrenière, Thierry Forveille, Jean-François Donati, Pascal Fouqué, Andrés Carmona, Ryan Cloutier, Paul Cristofari, Eric Gaidos, João Gomes da Silva, Lison Malo, Eder Martioli, J. -D. do Nascimento Jr., Stefan Pelletier, Thomas Vandal, Kim Venn. 2024-04-01. Comprehensive High-resolution Chemical Spectroscopy of Barnard's Star with SPIRou. https://arxiv.org/abs/2310.12125

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