A new wavelength calibration for echelle spectrographs using Fabry-Perot etalons

摘要: The study of Earth-mass extrasolar planets via the radial-velocity technique and measurement potential cosmological variability fundamental constants call for very-high-precision spectroscopy at level $\updelta\lambda/\lambda<10^{-9}$. Wavelength accuracy is obtained by providing two ingredients: 1) an absolute information-rich wavelength source 2) ability spectrograph its data reduction transferring reference scale (wavelengths) to a (detector pixels) in repeatable manner. goal this work improve calibration HARPS combining spectral provided emission lines thorium-argon hollow-cathode lamp (HCL) with spectrally rich precise information Fabry-Perot-based source. On basis frames acquired each night since Fabry-Perot etalon was installed on 2011, we construct combined solution which fits simultaneously thorium lines. fit anchored wavelengths, provide `zero-point' spectrograph, while are used (spectrally) local precision. verified auto-consistency tested against using Laser-Frequency Comb (LFC). thorium+Fabry-Perot shows significantly better performances compared thorium-only calibration. presented techniques will therefore be new HARPS-N pipeline, exported ESPRESSO spectrograph.