2025ApJ...978..154J

We extend the methodology introduced by F. Jahandar et al. to determine the effective temperature and chemical abundances of 31 slowly rotating solar neighborhood M dwarfs (M1-M5) using high-resolution spectra from CFHT/SPIRou. This group includes 10 M dwarfs in binary systems with FGK primaries of known metallicity from optical measurements. By testing our T_eff method on various synthetic models, we find a consistent inherent synthetic uncertainty of ∼10 K at a signal-to-noise ratio greater than 100. Additionally, we find that our results align with interferometric measurements, showing a consistent residual of -29 ± 31 K. Taking the inherent uncertainties into account, we infer the T_eff values of our targets and find an excellent agreement with previous optical and near-infrared studies. Our high-resolution chemical analysis examines hundreds of absorption lines using χ² minimization using PHOENIX-ACES stellar atmosphere models. We present elemental abundances for up to 10 different elements, including refractory elements such as Si, Mg, and Fe, which are important for modeling the interior structure of exoplanets. In binary systems, we find an average [Fe/H] of -0.15 ± 0.08 for M dwarfs, marginally lower than the reported metallicity of -0.06 ± 0.18 for the FGK primaries from A. W. Mann et al. We also observe slightly subsolar chemistry for various elements in our nonbinary M dwarfs, most notably for O, C, and K abundances. In particular, we find an average metallicity of -0.11 ± 0.16, lower but still consistent with the typical solar metallicity of FGK stars (e.g., [Fe/H] = 0.04 ± 0.20 from J. M. Brewer et al. 2016). This study highlights significant discrepancies in various major M dwarf surveys likely related to differences in the methodologies employed.