SOPHIE+: First results of an octagonal-section fiber for high-precision radial velocity measurements

F. Bouchy, R. F. Díaz, G. Hébrard, L. Arnold, I. Boisse, X. Delfosse, S. Perruchot, A. Santerne

Abstract
High-precision spectrographs play a key role in exoplanet searches and Doppler asteroseismology using the radial velocity technique. The 1 ms^-1 level of precision requires very high stability and uniformity of the illumination of the spectrograph. In fiber-fed spectrographs such as SOPHIE, the fiber-link scrambling properties are one of the main conditions for high precision. To significantly improve the radial velocity precision of the SOPHIE spectrograph, which was limited to 5–6 ms^-1, we implemented a piece of octagonal-section fiber in the fiber link. We present here the scientific validation of the upgrade of this instrument, demonstrating a real improvement. The upgraded instrument, renamed SOPHIE+, reaches radial velocity precision in the range of 1–2 ms^-1. It is now fully efficient for the detection of low-mass exoplanets down to 5–10 M_⊕ and for the identification of acoustic modes down to a few tens of cm s^-1.

Keywords
instrumentation: spectrographs – techniques: radial velocities – planetary systems – stars: oscillations

Astronomy and Astrophysics
Volume 549, Page A49_1
January 2013

DOI: 10.1051/0004-6361/201219979
ADS Bibliographic code: 2013A%26A...549A..49B