Lessons from the OGLE planetary transit survey Frdric

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Lessons from the OGLE planetary transit survey Frédéric Pont Geneva Observatory Francois Bouchy (Marseille/OHP),

Lessons from the OGLE planetary transit survey Frédéric Pont Geneva Observatory Francois Bouchy (Marseille/OHP), Nuno Santos (Lisbon), Claudio Melo (ESO), Didier Queloz, Shay Zucker, Stephane Udry, Michel Mayor (Geneva), Claire Moutou (Marseille) Corot Week 9 ESTEC 5 -9 Dec 2005

FLAMES follow-up of OGLE candidates 137 shallow transit candidates published by OGLE 60 followed

FLAMES follow-up of OGLE candidates 137 shallow transit candidates published by OGLE 60 followed in radial velocity by our team with FLAMES (15<V<18) FLAMES : 7 -fiber link to high-resolution spectro UVES on the VLT R ~ 45’ 000 45 mn on mv=17 S/N ~ 8 ~30 m/s Field of view 25’x 25’ 5 transiting planets detected Corot Week 9 ESTEC 5 -9 Dec 2005

Nature of planetary transit mimics deep transits Eclipsing binaries - grazing - low-mass companion

Nature of planetary transit mimics deep transits Eclipsing binaries - grazing - low-mass companion - multiple systems and blends False positive of the transit detection Corot Week 9 ESTEC 5 -9 Dec 2005 shallow transits

Planetary transit mimics II: small stellar companion Light curve can be undistinguishable from planetary

Planetary transit mimics II: small stellar companion Light curve can be undistinguishable from planetary transit OGLE-TR-122 b, Pont et al. 2005 can be impossible to discriminate from light curve easy with high-resolution spectroscopy Corot Week 9 ESTEC 5 -9 Dec 2005

Planetary transit mimics III: multiple system or blend Wide range of possible scenarios Light

Planetary transit mimics III: multiple system or blend Wide range of possible scenarios Light curve CMD Requires global analysis, light curve + radial velocity Often more than one component visible in the spectrum (but not always) Triple system can also mimic planetary RV variation! OGLE-TR-33 Torres et al. 2004 (GSC 01944 -02289 Mandushev et al. 2005) ranges from easy to very tricky to discriminate Corot Week 9 ESTEC 5 -9 Dec 2005 RV

Implications of planetary transit mimic scenarios • RV follow-up essential part of photometric transit

Implications of planetary transit mimic scenarios • RV follow-up essential part of photometric transit surveys required to establish planetary nature of Gas Giant candidates Corot Week 9 ESTEC 5 -9 Dec 2005

What are the contaminants for super-Earth transits ? Transiting M-dwarfs like OGLE-TR-122 will not

What are the contaminants for super-Earth transits ? Transiting M-dwarfs like OGLE-TR-122 will not be a problem BUT Gravitationally bound triple system will still be a source of mimics (how good mimics? To be studied) Background eclipsing binaries will be very numerous. “Corot. Lux” simulator (Guillot et al. ) --> ~100 -200 per field Most of these will be easy to discriminate Corot Week 9 ESTEC 5 -9 Dec 2005

Detection threshold of transit signal Corot Week 9 ESTEC 5 -9 Dec 2005

Detection threshold of transit signal Corot Week 9 ESTEC 5 -9 Dec 2005

1990 1995 2000 2005 2010 2015 0 0 1 0 0 0 5 0

1990 1995 2000 2005 2010 2015 0 0 1 0 0 0 5 0 0 0 Corot Week 9 ESTEC 5 -9 Dec 2005

Colours of noise white red pink Corot Week 9 ESTEC 5 -9 Dec 2005

Colours of noise white red pink Corot Week 9 ESTEC 5 -9 Dec 2005

Corot Week 9 ESTEC 5 -9 Dec 2005

Corot Week 9 ESTEC 5 -9 Dec 2005

Detection threshold with red noise (systematics) • Factor 3 -5 in threshold! • Weaker

Detection threshold with red noise (systematics) • Factor 3 -5 in threshold! • Weaker dependence on magnitude • Steeper dependence on period Corot Week 9 ESTEC 5 -9 Dec 2005

Transit detection significance with real photometric noise SNR 2 = depth 2 2 /

Transit detection significance with real photometric noise SNR 2 = depth 2 2 / n + 1/ n 2 cov(xi, xi) In the regime relevant to transit surveys, the red term dominates! white noise (photon+sky+scintillation) = 3 -10 mmag, n=20 -50, 2 / n = 0. 1 - 0. 5 mmag 2 red noise (systematics from seeing, weather, tracking) 1/ n 2 cov(xi, xi) = (3 -5 mmag)2 = 9 - 25 mmag 2 Corot Week 9 ESTEC 5 -9 Dec 2005

Second transiting planet around OGLE-TR-111 ? Corot Week 9 ESTEC 5 -9 Dec 2005

Second transiting planet around OGLE-TR-111 ? Corot Week 9 ESTEC 5 -9 Dec 2005

Application of revised yield estimates to some surveys affects also Gillon et al. 2005

Application of revised yield estimates to some surveys affects also Gillon et al. 2005 Corot Week 9 ESTEC 5 -9 Dec 2005

The hour-scale systematics of ground-based surveys: does the atmosphere set a hard limit ?

The hour-scale systematics of ground-based surveys: does the atmosphere set a hard limit ? - site / optics /detector / photometric reduction - covariance removal (SYS-REM, Tamuz et al. 2004) - modify tradeoff systematics vs random error There may be a practical limit for ground-based wide-field photometry (due to number of comparison star compared to number of correction parameters and total variation of flux) We find r 3 mmag for all large ongoing surveys ! Detection of transiting Neptunes from ground prevented by red noise. Corot Week 9 ESTEC 5 -9 Dec 2005

Implications for Corot ? COROT r = 0. 7 mmag according to Corot instrument

Implications for Corot ? COROT r = 0. 7 mmag according to Corot instrument team r = 2. 2 mmag according to realistic blind-test simulations [Moutou et al. 2005] High predicted yield of transiting Hot Jupiters due to large time coverage (150 x 24 hrs) Sensitivity to Super-Earth will depend on level of actual red noise Corot Week 9 ESTEC 5 -9 Dec 2005