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

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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) ,

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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%

    A~10 %)

  • 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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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)


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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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Detection of 17 SB1

1 peak but high RV Variation

SB2 et SB1 Detections

Detection of 16 SB2

  • Easily detected (2 correlation peaks)


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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 > 182 detections per COROT Field


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THANKS !!


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