Autoguider locked on a fiber input for precision stellar radial velocities^*

Service d'Aéronomie du CNRS, BP. 3, F-91371 Verrières-le-Buisson Cedex, France

Send offprint request to: F. Bouchy

Received: 23 October 1998
Accepted: 7 December 1998

Abstract

Measurement of stellar radial velocities (RV) is one acknowledged approach for planetary-search and asteroseismology programs. We study the incomplete scrambling action of a fiber feeding a spectrograph, which leaves RV errors at a level of few m/s. Observations realised with the ELODIE fiber-fed crossed-dispersion spectrograph at the 193-cm telescope of Observatoire de Haute-Provence (OHP) are presented. A fiber-locked autoguider (called FLAG) has been specifically built to reduce the stellar-beam geometrical fluctuations within the spectrograph. With FLAG, the fiber-input plays the role of guiding detector. Automatic focusing is also accomplished by the system. The design and performance characteristics of the instrument tested at the 152-cm telescope of OHP are reviewed here.