A new spectrograph dedicated to precise stellar radial velocities

Abstract

AbstractThe fiber-fed echelle spectrograph EMILIE designed for the measurement of stellar radial-velocity changes is presently being laboratory-tested. Using a 204 × 408 mm grating and a 1k × 1k CCD detector, it samples about 50% of the 410−620 nm wavelength range with spectral resolution R ∼ 150 000. This spectrograph is coupled to the telescope via a single 50μm fiber, which accepts 2.7 arcsec from the sky. An automatic guiding system stabilizes the image at the entrance of the fiber. The fiber transmits alternately to the spectrograph the stellar beam and the reference beam. The same pixels of the CCD detector are used alternately for the two spectra, which requires an excellent short term stability. Hence, later on, the spectrograph will be located within a vacuum tank, with active thermal control. The instrument will be set up at the focus of the 1.52-m coudé telescope at the Observatoire de Haute-Provence (OHP) and will undertake programs of asteroseismology and detection of extrasolar-planets.