The SPIRou wavelength calibration for precise radial velocities in the near infrared
Mélissa J. Hobson, F. Bouchy, Neil J. Cook, Étienne Artigau, C. Moutou, I. Boisse, C. Lovis, A. Carmona, X. Delfosse, J.‐F. Donati, the SPIRou Team
Abstract
Aims. SPIRou is a near-infrared (nIR) spectropolarimeter at the CFHT, covering the YJHK nIR spectral bands (980−2350 nm). We describe the development and current status of the SPIRou wavelength calibration in order to obtain precise radial velocities (RVs) in the nIR. Methods. We make use of a UNe hollow-cathode lamp and a Fabry-Pérot étalon to calibrate the pixel-wavelength correspondence for SPIRou. Different methods are developed for identifying the hollow-cathode lines, for calibrating the wavelength dependence of the Fabry-Pérot cavity width, and for combining the two calibrators. Results. The hollow-cathode spectra alone do not provide a sufficiently accurate wavelength solution to meet the design requirements of an internal error of < 0.45 m s −1 , for an overall RV precision of 1 m s −1 . However, the combination with the Fabry-Pérot spectra allows for significant improvements, leading to an internal error of ∼0.15 m s −1 . We examine the inter-night stability, intra-night stability, and impact on the stellar RVs of the wavelength solution.