1. Search for planetary candidates within the OGLE stars Adriana V. R. Silva & Patrícia C. Cruz CRAAM/Mackenzie COROT 2005 - 05/11/2005

2. Summary  Method to distinguish between planetary and stellar companions;  Observed transits in OGLE data: –177 stars;  Model: –Orbital parameters: P; r/R s, a/R s, i –Kepler’s 3 rd law + mass-radius relation for MS stars  Results tested on 7 known bonafide planets;  28 proposed planetary candidates for spectroscopic follow up  Silva & Cruz – Astrophysical Journal Letters, 637, 2006 (astro-ph/0505281)

3. Planet definition  Based on the object’s mass According to the IAU WORKING GROUP ON EXTRASOLAR PLANETS (WGESP):  stars: objects capable of thermonuclear fusion of hydrogen (>0.075 M sun );  Brown dwarf: capable of deuterium burning (0.013<M<0.075 M sun );  Planets: objects with masses below the deuterium fusion limit (M<13 M Jup ), that orbit stars or stellar remains (independently of the way in which they formed).

5. Newton’s gravitation law  Both planet and star orbit their common center-of-mass.  Planet’s gravitational attraction causes a small variation in the star’s light.  The effect will be greater for close in massive planets.

6. Extra-solar Planets Encyclopedia  www.obspm.fr/encycl/encycl.html  169 planets (until 24/10/2005): –145 planetary systems –18 multiple planetary systems  9 transiting: HD 209458, TrES-1, OGLE 10, 56, 111, 113, 132, HD 189733, HD 149026.

7. Planetary mass determined: Radial velocity shifts

8. Venus transit – 8 June 2004

9. Transits

10. HD209458 In 2000, confirmation that the radial velocity measurements were indeed due to an orbiting planet.

11. Planetary detection by transits  Only 9 confirmed planets.  Orbits practically perpendicular to the plane of the sky (i=90 o ).  Radial velocity: planet mass;  Transit: planet radius and orbit inclination angle;  Ground based telescopes able to detect giant planets only. Satellite based observations needed for detection of Earth like planets.

12. OGLE project  177 planets with “transits”;  Only 5 confirmed as planets by radial velocity measurements (10, 56, 111, 113, 132).  OGLE data (Udalski 2002, 2003, 2004)  Published orbital period  Model the data to obtain: –r/R s (planet radius); –a orb /R s (orbital radius – assumed circular orbit); –i (inclination angle).

13. Transit simulation

14. Model  Star  white light image of the sun;  Planet  dark disk of radius r/R s ;  Transit: at each time interval, the planet is centered at a given position in its orbit (with a orb /R s and i) and the total flux is calculated;

15. Transit Simulation

16. Lightcurve   I/I=(r/R s ) 2, larger planets cause bigger dimming in brightness.  For Jupiter  1% decrease  Larger orbital radius (planet further from the star) yield shorter phase interval.  Inclination angle close to 90 o (a transit is observed).  Smaller angles, shorter phase interval;  Grazing transits for i<80 o. r a orb i

17. Orbit  Circular orbits;  Period from OGLE project;  Perform a search in parameter space for the best values of r/R s, a orb /R s, and i (minimum  2 ).  Error estimate of the model parameters from 1000 Monte Carlo simulation, taken from only those within 1 sigma uncertainty of the data; a orb

18. Test of the model  7 known planets: HD 209458, TrES-1, OGLE-TR-10, 56, 111, 113, and 132  OGLE-TR-122 which companion is a brown dwarf with M=0.092 M sun and R=0.12 R sun (Pont et al. 2005)  Synthetic lightcurve with random noise added. M 1 (M sun )M 2 (M sun )R 2 (R J )Semi-axis AU)angle Input4.000.323.90.07584 Output3.750.293.60.07485.3

19. OGLE 10 OGLE 56OGLE 111OGLE 113 OGLE 132 HD209458 OGLE 122test TrES-1

20. Model test results

21. Fit Parameters

22. Equations  4 unknowns: M 1, R 1, M 2, and R 2  Kepler’s 3 rd law:  Transit depth  I/I:  Mass-radius relationship for MS stars (Allen Astrophysical Quantities, Cox 2000) for both primary and secondary:

23. Model parameters

24. Planetary candidates selection  Density: –Densities < 0.7 to rule out big stars (O, B, A): 1-2% dimming due to 0.3-0.5 M sun companions: –Densities > 2.3 maybe due to M dwarfs or binary systems.  Radius of the secondary:  28 candidates

25. Model parameters 0.7<  <2.3 R 2 <1.5 R J

27. Comparison with other results  100% agreement with: –Elipsoidal variation: periodic modulation in brightness due to tidal effects between the two stars (Drake 2003, Sirko & Paczynski 2003) –Low resolution radial velocity obs. (Dreizler et al. 2002, Konacki et al. 2003) –Giants: espectroscopic study in IR (Gallardo et al. (2005)  6 stars (OGLE-49, 151, 159, 165, 169, 170) failed the criterion of Tingley & Sackett (2005) of  >1.

28. Conclusions  From the transit observation of a dim object in front of the main star, one obtains: –Ratio of the companion to the main star radii: r/R s ; –Orbital radius (circular) in units of stellar radius: a orb /R s ; –Orbital inclination angle, i, and period, P.  Combining Kepler’s 3 rd law, a mass-radius relation (R  M 0.8 ), and the transit depth  infer the mass and radius of the primary and secondary objects.  Model was tested successfully on 7 known planets.  28 planetary candidates: density between 0.7 and 2.3 solar density and secondary radius < 1.5 R J.  Method does not work for brown dwarfs with M  0.1 M sun and sizes similar to Jupiter’s.

29. CoRoT  Method can be easily applied to CoRoT observations of transits.