Recent Developments of Studies for Transiting Exoplanets

1. Recent Developments ofStudies for Transiting Exoplanets Norio Narita National Astronomical Observatory of Japan

2. Outline • Introduction of Science of Transiting Exoplanets • What’s New and What’s Going on Now? • Near Future Prospects

3. Planetary transits transit in the Solar System transit in exoplanetary systems (we cannot spatially resolve) 2006/11/9 transit of Mercury observed with Hinode slightly dimming

4. The first exoplanetary transits Charbonneau+ (2000) for HD209458b

5. Transiting planets are increasing So far 69 transiting planets have been discovered.

6. Why are transits interesting? We can characterize origin, structure, and environment of respective planets!

7. Scientific Subjects of Transits Ongoing • Mass-Size relation (structure) • The Rossiter-McLaughlin effect (origin) • Transmission Spectroscopy (environment) • Secondary Eclipses (environment) Near Future • Transit Timing Variations • Exo-Rings and Exo-Moons

8. Mass-Size Relation (too inflated) HAT-P-3 b (heavy core) TrES-4 b, etc Charbonneau et al. (2006)

9. The Rossiter-McLaughlin effect When a transiting planet hides stellar rotation, star planet planet the planet hides the approaching side → the star appears to be receding the planet hides the receding side → the star appears to be approaching radial velocity of the host star would have an apparent anomaly.

10. Transmission Spectroscopy star upper atmosphere planet dimming with excess absorption stellar line A tiny part of starlight passes through planetary atmosphere.

11. secondary eclipse secondary eclipse IRAC 8μm transit transit Knutson et al. (2007) Secondary Eclipse provide information of thermal emissions of the dayside

12. Transit Timing Variations (TTV) perturbing but not transiting planet (or exo-moon) orbit of transiting planet observer observer

13. Exo-Rings and Exo-Moons Taken by the Cassini spacecraft on September 15, 2006 (Credit: NASA/JPL/Space Science Institute)

14. Summary of Recent News • Discoveries of transiting super earths • Discoveries of highly tilted transiting planets • Kepler launched and recently announced results • Possible Transit Timing Variations? • Discovery of the largest Saturnian ring

15. 1: Discoveries of Transiting Super Earthsand their Meanings

16. First Transiting Super Earth CoRoT-7b CoRoT-7b: Rp=1.7 RearthMp=4.8 MEarth CoRoT-7: K0V star, d = 150 pc Leger et al. (2009), Queloz et al. (2009)

17. Second Discovery by MEarth Team GJ1214b: Rp=2.68 REarthMp=6.55 MEarth GJ1214: M4.5V star, d = 13 pc Charbonneau et al. (2009)

18. Previous Mass-Radius Relation inflated !! HAT-P-3 HD149026 Hartman et al. (2009)

19. Diversity of Jovian Planets (too inflated) HAT-P-3 b (heavy core) TrES-4 b, etc Charbonneau et al. (2006)

20. New Mass-Radius Relation Parameter space now comes to Earth-like region H+He Diversity of Earth-like planets pure H2O H2O dominated Earth-like Charbonneau et al. (2009)

21. 2: Discoveries of Highly Tilted Planetsand their Meanings

22. Do Such Planets Exist? Stellar Spin Planetary Orbit

23. Semi-Major Axis Distribution of Exoplanets Snow line Jupiter

24. Eccentricity Distribution Eccentric Planets Jupiter

25. Standard Migration Models Type I and II migration mechanisms • consider gravitational interaction between • proto-planetary disk and planets • Type I: less than 10 Earth mass proto-planets • Type II: more massive case (Jovian planets) • well explain the semi-major axis distribution • e.g., a series of Ida & Lin papers • predict small eccentricities and small inclination for migrated planets

26. Migration Models for Eccentric Planets • consider gravitational interaction between • planet-planet (planet-planet scattering models) • planet-binary companion (Kozaimigration) • may be able to explain eccentricity distribution • e.g., Nagasawa+ 2008, Chatterjee+ 2008 • predict a variety of eccentricities and also misalignments between stellar-spin and planetary-orbital axes ejected planet

27. The Rossiter-McLaughlin effect reflects the trajectory of planetary orbit in front of stellar surface misaligned (tilted) well aligned Radial velocity during transits = Keplerian motion + Rossiter effect Gaudi & Winn (2007)

28. Previous studies of the RM effect HD209458 Queloz+ 2000, Winn+ 2005 HD189733Winn+ 2006 TrES-1 Narita+ 2007 HAT-P-2 Winn+ 2007, Loeillet+ 2008 HD149026 Wolf+ 2007 HD17156 Narita+ 2008,2009, Cochran+ 2008, Barbieri+ 2009 TrES-2 Winn+ 2008 CoRoT-2 Bouchy+ 2008 XO-3 Hebrard+ 2008, Winn+ 2009 HAT-P-1Johnson+ 2008 HD80606Moutou+ 2009, Pont+ 2009, Winn+ 2009 WASP-14Joshi+ 2008, Johnson+ 2009 HAT-P-7 Narita+ 2009, Winn+ 2009 CoRoT-3 Triaud+ 2009 WASP-17 Anderson+ 2010 CoRoT-1 Pont+ 2010 WASP-3 Simpson+ 2010 Kepler-8 Jenkins+ 2010 TrES-4 Narita+ to be submitted HAT-P-13 Winn+ to be submitted Red: Eccentric Blue: Binary Green: Both

29. Summary of RM Studies • 4 out of 7 eccentric planets have highly tilted orbits • tilted planetary orbits may be common for eccentric planets • 3 out of 13 non-eccentric planets also show tilted orbits • spin-orbit misalignements are rare for non-eccentric planets • we can add samples to learn a statistical population of alinged/misaligned/retrograde planets • 2 out of 20 transiting planets show retrograde orbits • Distribution of spin-orbit alignment angles would be useful to test planetary migration models

30. 3: Kepler launched in 2009and recently announced results

31. Beginning of the Kepler Era Kepler launched on March 6, 2009 Just before the 5thExoplanet Conference in Kona Kepler website

32. First result announced in August 2009 heat transfer albedo Kepler website

33. Kepler website

34. Kepler Started Exploration • large number of Jovian, Neptunian, Earth-like planets will be discovered • Mass-Radius Distribution • Spin-Orbit Alignment Distribution • Albedo • Heat Transfer Many theoretical studies will be stimulated!

35. By the way… Kepler can determine transit times of transiting planets precisely. What can we do with the Kepler data.

36. 4: Observations of Transit Timing Variationsand Near Future Prospects

37. Transit Timing Variations (TTV) perturbing but not transiting planet (or exo-moon) orbit of transiting planet observer observer

38. Theoretical Studies • For another planet: • Agol et al. (2005) / Holman & Murray (2005) • a few min for a hot Jupiter having an earth-mass planet in 2:1 resonance orbit • If an earth-mass planet exists around a hot Jupiter, even ground-based telescope would be able to detect TTV • For exo-moon: • Kipping 2009a, 2009b, Kipping et al. (2009) • Exo-moons would be detectable with the Kepler

39. 1 0 O-C [min] -1 -2 case of no TTV 446 266 366 Transit Epoch Likely First Discovery of TTV an Earth-mass planet in 4:1 resonant orbit? Transit timing of OGLE-TR-111b (Diaz et al. 2008) and TTV in this system is ongoing.

40. Kepler will discover numbers of additional planets and exo-moons with TTV!

41. 5: Discovery of the Largest Saturnian Ringand Implication for Exo-Ring Exploration

42. Exo-Rings and Exo-Moons Enceladus Earth Taken by the Cassini spacecraft on September 15, 2006 (Credit: NASA/JPL/Space Science Institute)

43. Methodology of Ring Detection • Transit light curves for ringed planets are slightly different from those for no-ring planets • Residuals between observed light curves and theoretical planetary light curves are ring signals • Signals are typically ~10-4 level • Detectable with HST/Kepler • We can learn configuration of rings with high precision photometry Barnes & Fortney (2004)

44. Discovery of the Largest Saturnian Ring Largest ring extended from 128 RSaturnto 207RSaturn Verbiscer et al. (2009) (Credit: NASA/JPL Caltech/Keck) If we observe the Saturn as a transiting planet, differences of multiband transit light curves are quite large!

45. Characterization of Particle Size of Rings • Diffractive forward-scattering depends on ring’s particle size and causes difference in • depth of transit light curve • ramp just before and after transits • Multi-wavelength observations would be useful to characterize distribution of particle size • SPICA’s wide wavelength coverage is useful to probe wide variety of particle size Barnes & Fortney (2004) (for 0.5 micron observations)

46. Next Generation Telescopes James Webb Space Telescope  SPICA after 2014 after 2018 Thirty Meter Telescope  after 2018

47. Summary Transit observations provide us various interesting information to characterize extrasolar planets!

48. Questions?