Datasets

While various very-high (\(\lambda/\delta\lambda>50\,000\)) resolution spectrographs covering most or all of the near-infrared domain at once are currently under design or construction (e.g., Carmenes, SPIRou, PRVS), none is currently in operation. As a result, very-high resolution spectra available in archives only cover relatively short wavelength intervals. The only publicly available spectrum of an M dwarf at a resolution sufficient to resolve the intrinsic stellar line width (\(\sim5\,km/s\) or \(\lambda/\delta\lambda>60\,000\)) is that available through the CRIRE-POP¹ spectral library for the Barnard star ( refcrirespop). These observations cover the \(Y\), \(J\), \(H\), \(K_s\), \(L\) and \(M\) bands; of specific interest here being the \(\lt 2.38\mu\)m domain that is amenable to m/s-level accuracy velocimetry. As the sole M dwarf with complete near-infrared coverage at this resolution, Barnard’s Star is a relatively convenient choice as, with an M4.0V spectral type it is representative of field M dwarfs that will be targeted by upcoming near-infrared radial-velocity surveys. For earlier M dwarfs, optical spectrographs are competitive against near-infrared spectrographs. Vert late M dwarfs (\(\gt\)M7V) are even more promising targets for nIR velocimetry, but are generally fast rotators, even at ages of Gyr refxavier. Furthermore, the rotation period of Barnard’s star is known to be very long (130.4days; http://arxiv.org/pdf/astro-ph/9806276v1.pdf). With a interferometrically determined radius of \(0.196\pm0.008\) (http://arxiv.org/pdf/0906.0602v1.pdf), the rotational broadening is \(\lt76\)m/s. This value is about two orders of magnitudes smaller than the intrinsic line width of M dwarfs. The only peculiarity regarding Barnard’s star relative to the bulk of field star is that it is a metal-poor thick disk star. This affects the radial velocity content of its spectrum. This is addressed in section \ref{metallicityQ}