P. Bordé 1, B. Samuel 1, A. Léger 1, M. Ollivier 1 & D. Rouan 2 1 IAS, Université Paris-Sud 11 2 LESIA, Observatoire de Paris First International Corot Symposium 2-5 February 2009, Paris Using Corot colors to discriminate between planetary transit candidates

02/02/09Bordé et al. - Corot colors2 3-color photometry with Corot

02/02/09Bordé et al. - Corot colors3 3-color light curves 80 % 10 %

02/02/09Bordé et al. - Corot colors4 3-color transits Planetary transits are expected to have identical depths in all channels.

02/02/09Bordé et al. - Corot colors5 Detecting non planetary transits #1 étoile de 1 er plan Foreground target Background eclipsing binary Spatial use of colors: One or two colors without measurable transit.

02/02/09Bordé et al. - Corot colors6 Detecting non-planetary transits #2 étoile de 1 er plan Complete overlap with background EB Giant-dwarf grazing EB Triple system with an EB Transit depth will vary according to the color.

02/02/09Bordé et al. - Corot colors7 An approach to color testing #1 1) Fit a trapezoid to the white (red+green+blue) folded transit 2) Get measurements inside every individual transit in each color 3) Perform Student's t tests for statistically different means ∆F/F t 14 t 23

02/02/09Bordé et al. - Corot colors8 An approach to color testing #2 Let x B and x R be the series of n measurements inside the blue and red transits. Compute Significance of depth difference is given by with

02/02/09Bordé et al. - Corot colors9 Rejecting a specific hypothesis #1 A white LC analysis leads to 2 possible scenarios:  planetary transit;  K2V star blended with a M5V-M8V EB.

02/02/09Bordé et al. - Corot colors10 Rejecting a specific hypothesis #2  Expected:b = 0.17,g = 0.25, r = 1.30  Measured:b = 1.42 ± 0.41,g = 1.24 ± 0.30,r = 0.88 ± 0.18

02/02/09Bordé et al. - Corot colors11 Summary Corot 3-color photometry can be used to:  detect and correct instrumental effects (e.g., hot pixels);  suspect or disprove alternative hypotheses to planetary transits, such as: giant-dwarf grazing eclipsing binaries; background eclipsing binaries; triple systems including eclipsing binaries.