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GIRAFFE (VLT): A new tool for exoplanets preparatory observations and follow-up Benoît Loeillet (LAM) ,

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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). GIRAFFE observations.

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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)

giraffe observations
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

hot jupiter expected
Hot Jupiter expected

Main Objectives: - Detection of hot Jupiters

- Identification of binary stars

- Spectroscopic Characterization of stellar population

targets observed
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%

A~10 %)

  • mv = 11 → 16
giraffe spectrum
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

cross correlation method ccf

FWHM

Contrast

RV

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)

instrument stability
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

sb2 et sb1 detections
Detection of 17 SB1

1 peak but high RV Variation

SB2 et SB1 Detections

Detection of 16 SB2

  • Easily detected (2 correlation peaks)
conclusion
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
rv follow up perspectives
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 > 182 detections per COROT Field

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