Visible spEctroGraph and polArimeter : VEGA on CHARA



Workshop on a future generation visible interferometric combiner  

14th and 15th of February, NEF, Mt. Gros, 

Observatoire de la Côte d'azur (Nice)

First announcement

The VEGA recombiner on CHARA interferometer is operating since five years now and has proven its capabilities through many publications in stellar physics (, with mainly two topics concerned:
  1. the fundamental stellar parameters thanks to the unprecedented angular resolution (0.3 mas) obtained with the 300m baselines of CHARA coupled with the visible wavelength range of VEGA,
  2. the kinematical study of circumstellar environments using the coupling of high-angular and high-spectral resolution (R=30000) of the VEGA instrument.
The instrument is however limited by the precision of the measurements, either on faint objects or at low visibilities. This limitation introduced by the multimode regime and by the limitation of the photon counting detectors restricts many scientific programs. Within few years, the CHARA interferometer will be equipped with new adaptive optics opening unique possibilities for VEGA. In parallel, a brainstorming for the future development of the VLTI at the time of the ELT operation has started and an initial proposition for a visible operation of the VLTI has been recently submitted ( Other developments are also under progress NPOI / VISION (

In this framework, we have started at the Lagrange Laboratory preliminary studies for a new concept of visible instrument (VEGAS) based on optical fibers and up-to-date detectors. This research and development has begun through the development of a laboratory prototype and we would like to open more widely the think-tank, on the instrument concept itself accordingly to the proposed science prospective.

VEGAS intends to measure visibilities in the optical with good precision on very faint objects (up to magnitude 10-11). Based on the expected performances (described in this document: vegas_performances.pdf), we propose to organize a workshop where the exciting science that could be done will be discussed in parallel also to the kind of technical concept/configuration that would be required to reach these objectives.

We thus organize a two-day workshop beginning of 2013 (in Nice, Mt Gros) in order to :
- list all science cases for a future visible combiner and more specifically for this new VEGAS concept
- optimize the technical concept/configuration of VEGAS based on science cases : number of telescopes, spectral resolution, wavelength...

If you are interested could you please (deadline : December 7th):
- fill the following doodle :
- and send an e-mail to and if you wish to give a talk (a short title would be appreciated to prepare the program).


Ph. Berio
O. Chesneau
A. Chiavassa
J.-M. Clausse
O. Creevey
P. Cruzalebes
A. Domiciano
G. Duvert
N. Fabas
P. Kervella
J.-B. Le Bouquin
T. Lanz
R. Ligi
G. Martin
A. Meilland
F. Millour
D. Mourard
N. Nardetto
K. Perraut
A. Spang
I. Tallon-Bosc
F. Thevenin

Programme Scientifique: 

Jeudi 14 Fevrier 2013

9h30-9h45: Accueil
9h45-10h: "Vers une nouvelle génération d'instrument interférométrique visible: premières réflexions"  (Ph. Berio) - pdf
10h-10h30: "VEGAS dans le Contexte VLTI" (F. millour) - pdf
10h30-11h: "Nulling de cloture de phase" (G. Duvert) - pdf
11h-11h30: PAUSE
11h30-12h: "Intérêt de l'interférométrie visible pour l'étude des étoiles chaudes actives" (A. Meilland) - pdf
12h-12h30: "astero + interfero" ou "etoiles pauvres en metaux" (O. Creevey) - pdf

12h30-14h: BUFFET avec discussions informelles

14h-14h30: "Bételgeuse et les étoiles supergéantes rouges" (P. Kervella) - pdf

14h30-15h: "Prospects about interfero-polarimetric observations of Mira-type variable stars with VEGAS" (N. Fabas) - pdf

15h-15h30: "Cepheides" (N. Nardetto) - pdf

15h30-16h: PAUSE

16h-16h30: "Cas scientifique relatif à la cinématique et à l'imagerie des
régions internes des objets jeunes" (K. Perraut) - pdf

16h30-17h: "Activité stellaire et transits vus par l'interférométrie" (R. Ligi)  - pdf

Vendredi 15 Fevrier 2013

9h30-10h: "Vers une nouvelle génération d'instrument interférométrique visible: premiers tests"  (Ph. Berio) - pdf

10h-10h30: R&D Grenoble (K. Perraut) - pdf
10h30-11h: R&D Paris (E. Huby) - pdf
11h-12h: Discussion Générale sur VEGAS (en se basant sur la synthèse des spécifications) (O.Chesneau) - pdf
12h-14h: BUFFET avec discussions informelles

Webmaster: N. Nardetto (05/02/2013)