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| Paper: |
A New Spectrograph Dedicated to Precise Stellar Radial Velocities |
| Volume: |
185, Precise Stellar Radial Velocities, IAU Colloquium 170 |
| Page: |
22 |
| Authors: |
Bouchy, F.; Connes, P.; Bertaux, J. L. |
| Abstract: |
The fibre-fed echelle spectrograph EMILIE designed for the measurement of stellar radial-velocity changes is presently being laboratory-tested. Using a 204x408 mm echelle grating and a 1kx1k CCD detector, it samples about 50% of the wavelength range between 420 and 660 nm (50 echelle orders) with spectral resolution R ~150 000. This spectrograph is coupled to the telescope via a single 50-mu m fibre, which accepts 2.7 arcsec from the sky, and an image-slicer. An automatic guiding and focusing system stabilises the rapid image motion caused by atmospheric turbulence at the entrance of the fibre. Correction is accomplished up to a closed-loop frequency of ~100 Hz and uses the fibre entrance itself as position detector. The fibre transmits alternately to the spectrograph the stellar beam and the reference beam coming from a tunable Fabry-Perot interferometer illuminated by a white-light source. This interferometer generates a channeled spectrum which follows the stellar line shifts (see abstract by J. Schmitt). The same pixels of the CCD detector are used alternately for the two spectra, which requires an excellent short-term stability (i.e. over times of 10 to 100 s). Hence, later on, the spectrograph will be hung by steel cables in a vacuum tank, with active thermal control. By coupling EMILIE with the AAA, we hope to reduce errors to the 1 m/s level. The instrument will be installed at the focus of the 1.52-m coude telescope at the Haute-Provence Observatory and should begin programs of asteroseismology and detection of extrasolar planets. |
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