• DOI:10.1051/0004-6361/200913016
• Corpus ID: 10649317

VEGA: Visible spEctroGraph and polArimeter for the CHARA array: principle and performance

@article{Mourard2009VEGAVS,
  title={VEGA: Visible spEctroGraph and polArimeter for the CHARA array: principle and performance},
  author={Denis Mourard and J. M. Clausse and Aur{\'e}lie Marcotto and K. Perraut and I. Tallon-Bosc and Philippe B{\'e}rio and Alain Blazit and Daniel Bonneau and Sandra Bosio and Yves Bresson and Olivier Chesneau and Omar Delaa and François H{\'e}nault and Y. Hughes and St'ephane Lagarde and Guy Merlin and Alain Roussel and Alain Spang and P. Stee and Michel Tallon and Pierre Antonelli and Renaud Foy and Pierre Kervella and Romain G. Petrov and {\'E}ric Thi{\'e}baut and Farrokh Vakili and Harold A. Mcalister and Theo A. ten Brummelaar and Judit Sturmann and Laszlo Sturmann and Nils H. Turner and Christopher D. Farrington and P. J. Goldfinger},
  journal={Astronomy and Astrophysics},
  year={2009},
  volume={508},
  pages={1073-1083}
}

• D. Mourard, J. Clausse, +30 authors P. J. Goldfinger
• Published 1 December 2009
• Physics
• Astronomy and Astrophysics

Context. Among optical stellar interferometers, the CHARA Array located at Mt Wilson in California offers the potential of very long baselines (up to 330 m) and the prospect of coupling multiple beam combiners. This paper presents the principle and the measured performance of VEGA, Visible spEctroGraph and polArimeter installed in September 2007 at the coherent focus of the array. Aims. With 0.3 ms of arc of spatial resolution and up to $30 000$ of spectral resolution, VEGA intends to measure fundamental parameters of stars, to study stellar activities and to image and analyze circumstellar environments. We describe the observing modes that have been implemented for this spectro-polarimeter and show actual performances measured on the sky during the first observing runs. Methods. The astrophysical programs are described in relation to the observing modes of the instrument, the presentation of the spectrograph and of the interface table is shown and finally the data is presented. We discuss the perspectives of further development in the framework of the CHARA Array. Results. We show that VEGA/CHARA is fully operational. The current limiting magnitude is nearly 7 but the results depend on the observing conditions (seeing, spectral resolution, etc.). We have validated the stability of the instrumental visibility at the level of 1 to 2% over half an hour and of the instrumental polarization for various declinations. Some examples of squared visibility and differential visibility are presented. Conclusions. The spectro-polarimeter VEGA has been installed and successfully tested on CHARA. It will permit stellar physics studies at unprecedented spectral and spatial resolutions.