GIRAFFE VLT: A new tool

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• GIRAFFE (VLT) A new tool
• for exoplanets preparatory observations and
• follow-up
• Benoît Loeillet (LAM),
• François Bouchy, Magali Deleuil, Claire Moutou,
  Jean-Claude Bouret (LAM), Frédéric Royer (GEPI
  Paris Meudon),Frédéric Pont (Observatoire de
  Genève)

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GIRAFFE observations

• Multi-fiber Spectrograph up to 132
  objects
• Simultaneous Calibration with a Th-Ar lamp
• R 25000
• Survey of 645 stars 1 spectra each
  night for 5 nights

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Hot Jupiter expected
Main Objectives - Detection of hot
Jupiters - Identification of binary
stars - Spectroscopic Characterization of
stellar population
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Targets Observed

• HD 49454 - HD 49933 Field
• (Anticenter)
• Priority selection based on previous photometric
  spectral classification (Exodat)
• F,G,K IV V 60
• III 30
• A10 )
• mv 11 ? 16

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GIRAFFE spectrum

• Spectral range
• 5150 5350 Å
• mV 12 ? S/N 100
• mV 14 ? S/N 50
• mV 15 ? S/N 30
• In 30 min Exposure time

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Cross Correlation Method (CCF)

• Default Correlation Mask G2V (solar type)
• Gaussian fit of a CCF gives
• Radial Velocity(km.s-1)
• FWHM (km.s-1)
• Contrast ()
• Empirical Determination of photon noise
  uncertainty
• (Bouchy et al. 05)

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Instrument Stability

• Less than 10 m.s-1 can be reached for photon
  noise uncertainty
• A Systematic Error 50 m.s-1
• Effort in progress to reduce systematic

50 m.s-1
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SB2 et SB1 Detections

• Detection of 16 SB2
• Easily detected (2 correlation peaks)

• Detection of 17 SB1
• 1 peak but high RV Variation

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ExoPlanets/brown dwarfs candidates
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Conclusion

• 9 exoplanets/brown dwarfs candidates detected in
  only 5 half-nights of observations.
• BUT need confirmation thanks to SOPHIE (OHP),
  HARPS (3.6m - ESO), UVES (FLAMES), ...
• If confirmed, good candidates for direct
  Over-sampling observation with COROT

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RV Follow-up Perspectives

• High Potential of the GIRAFFE instrument
  efficient detection of binaries and massive
  exoplanets
• Precision similar to UVES/FLAMES (Bouchy et al.,
  Pont et al. 05 )
• Possible Follow-up of transiting Hot Jupiter
  (with known period phase)
• More efficient than UVES/FLAMES (7 fibers)
• if alarm rate gt 182 detections per COROT
  Field

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THANKS !!