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Description
SPIRou is a near-infrared (nIR) spectropolarimeter at the CFHT, covering the YJHK nIR spectral bands (980-2350nm). We describe the development and current status of the SPIRou wavelength calibration in order to obtain precise radial velocities (RVs) in the nIR. We make use of a UNe hollow-cathode lamp and a Fabry-Perot etalon 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-Perot cavity width, and for combining the two calibrators. The hollow-cathode spectra alone do not provide a sufficiently accurate wavelength solution to meet the design requirements of an internal error of <0.45m/s, for an overall RV precision of 1m/s. However, the combination with the Fabry-Perot spectra allows for significant improvements, leading to an internal error of 0.15m/s. We examine the inter-night stability, intra-night stability, and impact on the stellar RVs of the wavelength solution.
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