1. Characterization of Planets: Mass and Radius (Transits Results Part I) I. Results from individual transit search programs II. Interesting cases III. Global Properties IV. Spectroscopic Transits

2. The first time I gave this lecture (2003) there was one transiting extrasolar planet There are now 59 transiting extrasolar planets First ones were detected by doing follow-up photometry of radial velocity planets. Now transit searches are discovering exoplanets

3. Radial Velocity Curve for HD 209458 Period = 3.5 days Msini = 0.63 M Jup

4. Charbonneau et al. (2000): The observations that started it all: Mass= 0,63 M Jupiter Radius = 1,35 R Jupiter Density = 0,38 g cm – 3

5. Transit detection was made with the 10 cm STARE Telescope

7. A light curve taken by amateur astronomers…

8. ..and by the Profis ( Hubble Space Telescope).

9. HD 209458b has a radius larger than expected. HD 209458b Models I, C, and D are for isolated planets Models A and B are for irradiated planets. Evolution of the radius of HD 209458b and  Boob One hypothesis for the large radius is that the stellar radiation hinders the contraction of the planet (it is hotter than it should be) so that it takes longer to contract. Another is tidal heating of the core of the planet if you have nonzero eccentricity Burrows et al. 2000

10. Successful Transit Search Programs OGLE: Optical Gravitational Lens Experiment (http://www.astrouw.edu.pl/~ogle/)http://www.astrouw.edu.pl/~ogle/ 1.3m telescope looking into the galactic bulge Mosaic of 8 CCDs: 35‘ x 35‘ field Typical magnitude: V = 15-19 Designed for Gravitational Microlensing First planet discovered with the transit method 8 Transiting planets discovered so far

11. The first planet found with the transit method

12. Konacki et al. Until this discovery radial velocity surveys only found planets with periods no shorter than 3 days. About ½ of the OGLE planets have periods less than 2 days.

13. M = 1.03 M Jup R = 1.36 R jup Period = 3.7 days

14. K = 510 170 m/s i= 79.8 0.3 a= 0.0308 Mass = 4.5 M J Radius = 1.6 R J Spectral Type = F3 V Vsini = 40 km/s One reason I do not like OGLE transiting planets. These produce low quality transits, they are faint, and they take up a large amount of 8m telescope time.

15. Successful Transit Search Programs WASP: Wide Angle Search for Planets (http://www.superwasp.org). Also known as SuperWASPhttp://www.superwasp.org Array of 8 Wide Field Cameras Field of View: 7.8 o x 7.8 o 13.7 arcseconds/pixel Typical magnitude: V = 9-13 15 transiting planets discovered so far

20. Coordinates RA 00:20:40.07 Dec +31:59:23.7 ConstellationPegasus Apparent Visual Magnitude11.79 Distance from Earth1234 Light Years WASP-1 Spectral TypeF7V WASP-1 Photospheric Temperature 6200 K WASP-1b Radius1.39 Jupiter Radii WASP-1b Mass0.85 Jupiter Masses Orbital Distance0.0378 AU Orbital Period2.52 Days Atmospheric Temperature1800 K Mid-point of Transit2453151.4860 HJD

21. WASP 12: Hottest (at the time) Transiting Planet Discovery data High quality light curve for accurate parameters Doppler confirmation Orbital Period: 1.09 d Transit duration: 2.6 hrs Planet Mass: 1.41 M Jupiter Planet Radius: 1.79 R Jupiter Planet Temperature: 2516 K Spectral Type of Host Star: F7 V

22. Mass: 60 M Jupiter Radius: 1 R Jupiter Teff: ~ 2800 K Planet Mass: 1.41 M Jupiter Planet Radius: 1.79 R Jupiter Planet Temperature: 2516 K Comparison of WASP 12 to an M8 Main Sequence Star WASP 12 has a smaller mass, larger radius, and comparable effective temperature than an M8 dwarf. Its atmosphere should look like an M9 dwarf or L0 brown dwarf

23. Mass – Radius Relationship Stars Planets

24. Successful Transit Search Programs TrES: Trans-atlantic Exoplanet Survey (STARE is a member of the network http://www.hao.ucar.edu/public/research/stare/) http://www.hao.ucar.edu/public/research/stare/ Three 10cm telescopes located at Lowell Observtory, Mount Palomar and the Canary Islands 6.9 square degrees 4 Planets discovered

25. TrEs 1b

26. TrEs 2b P = 2.47 d M = 1.28 M Jupiter R = 1.24 R Jupiter i = 83.9 deg

27. Successful Transit Search Programs HATNet: Hungarian-made Automated Telescope (http://www.cfa.harvard.edu/~gbakos/HAT/ Six 11cm telescopes located at two sites: Arizona and Hawaii 8 x 8 square degrees 12 Planets discovered

28. Follow-up with larger telescope HAT-P-1b

29. HAT-P-1b has an anomolously large radius for its mass

30. HAT-P-12b Star = K4 V Planet Period = 3.2 days Planet Radius = 0.96 R Jup Planet Mass = 0.21 M Jup (~M Sat )  = 0.3 gm cm –3

31. Special Transits: GJ 436 Host Star: Mass = 0.4 M סּ (M2.5 V) Butler et al. 2004

32. „Photometric transits of the planet across the star are ruled out for gas giant compositions and are also unlikely for solid compositions“ Special Transits: GJ 436 Butler et al. 2004

33. The First Transiting Hot Neptune Gillon et al. 2007

34. Star Stellar mass [ M סּ ]0.44 ( ± 0.04) Planet Period [days]2.64385 ± 0.00009 Eccentricity0.16 ± 0.02 Orbital inclination86.5 0.2 Planet mass [ M E ]22.6 ± 1.9 Planet radius [ R E ]3.95 +0.41 -0.28 Special Transits: GJ 436 Mean density = 1.95 gm cm –3, in between Neptune (1.58) and Uranus (2.3)

35. M = 3.11 M Jup Special Transits: HD 17156 Probability of a transit ~ 3%

36. R = 0.96 R Jup Barbieri et al. 2007 Mean density = 4.88 gm/cm 3 Mean for M2 star ≈ 4.3 gm/cm 3

37. Period = 2.87 d R p = 0.7 R Jup M p = 0.36 M Jup Sato et al. 2005 Special Transits: HD 149026 Mean density = 2.8 gm/cm 3

38. So what do all of these transiting planets tell us?

39. Solar System Object  (gm cm –3 ) Mercury5.43 Venus5.24 Earth5.52 Mars3.94 Jupiter1.33 Saturn0.70 Uranus1.30 Neptune1.76 Pluto2 Moon3.34 Carbonaceous Meteorites 2–3.5 Iron Meteorites7–87–8 Comets0.06-0.6 The density is the first indication of the internal structure of the exoplanet

40. HD 209458b and HAT-P-1b have anomalously large radii that still cannot be explained by planetary structure and evolution models Mass Radius Relationship

41. HAT-12b CoRoT-3

42. ~70 M earth core mass is difficult to form with gravitational instability. HD 149026 b provides strong support for the core accretion theory R p = 0.7 R Jup M p = 0.36 M Jup Mean density = 2.8 gm/cm 3 10-13 M earth core

43. GJ436b (transiting Neptune) has a density comparable to Uranus and Neptune and thus we expect similar structure

44. Take your favorite composition and calculate the mass-radius relationship

45. 5 4 3 2 1 110100 M/M E R/R E Ices Silicates Fe 75% H–25 % He U The type of planet you have (rock versus iron, etc) is driven largely by the radius determination. E.g.: a silicate planet can have a mass that varies by more than 20%. A 20% error in the radius determines whether the planet is a rock or a piece of iron. This is because density ~ M, but R –3 N GJ 436

46. To get a better estimate of the composition of an exoplanet, you need to know the radius of the planet to within 5% or better You need accurate transit depths → you should probably do this from space, or lots of measurements from the ground You only determine R planet /R star. This means you need to know the radius of the star to within a few percent. For accurate stellar radii you must use - Interferometry - Asteroseismology

47. The best fitting model for HAT-P-12b has a core mass ≤ 10 M earth and is still dominated by H/He (i.e. like Saturn and Jupiter and not like Uranus and Neptune. It is the lowest mass H/He dominated gas giant planet. HAT-P-12b

48. Global Properties

49. Planet Radius Most transiting planets tend to be inflated

50. Mass-Radius Relationship Radius is roughly independent of mass, until you get to small planets (rocks)

51. All Planets (mostly from Doppler surveys). 37% stars have mass greater than 1 M sun Transiting Planets: 45% Stars have mass greater that 1 M sun Mass of the Host Star However, probability of a transit is ~ R star /a, so this might be a selection effect.

52. Planet Mass Distribution It is rare to find close-in planets that have high mass, but they do exist. Some with masses up to 20 M Jup (CoRoT-3)

53. Astronomer‘s Metals More Metals ! Even more Metals !! The Planet-Metallicity Connection

54. Bracket Fe/H notation : [Fe/H] This is the ratio of metal abundance to the solar value. Often it is for Iron lines, but sometimes other heavy elements are included. Sometimes [M/H] is used for metals: [Fe/H] is calculated by taking the iron abundance, divide it by the abundance of iron in the sun, and then taking the logarithm base 10. [Fe/H] = 0 → solar abundance [Fe/H] = +0.5 →3.16 × solar [Fe/H] = –1.0 →0.1 × solar Most metal rich stars have [Fe/H] = +0.5, most metal poor have [Fe/H] ≈ –3

55. These are stars with metallicity [Fe/H] ~ +0.3 – +0.5 There is believed to be a connection between metallicity and planet formation. Stars with higher metalicity tend to have a higher frequency of planets. This has been used as evidence in support of the core accretion theory Valenti & Fischer The Planet-Metallicity Connection?

56. Transiting Planets All Planets (mostly from Doppler surveys) Comparison of Metalicity

57. Metallicity of Giant Stars also show no metallicity effect [Fe/H] % Red line: Main sequence (1 solar mass) Blue: Giants (~1.4 solar mass) Most planets around giant stars and transiting planets are for 1.2-1.4 M Sun host stars. And there seems to be no metallicity effect.

58. Endl et al. 2007: HD 155358 two planets and.. …[Fe/H] = –0.68. This certainly muddles the metallicity-planet connection Hyades stars have [Fe/H] = 0.2 and according to V&F relationship 10% of the stars should have giant planets, but none have been found in a sample of 100 stars More problems with Planet – Metallicity Connection

59. Early indications are that the host stars of transiting planets have different properties than non-transiting planets. Most likely explanation: Transit searches are not as biased as radial velocity searches. One looks for transits around all stars in a field, these are not pre- selected. The only bias comes with which ones are followed up with Doppler measurements Caveat: Transit searches are biased against smaller stars. i.e. the larger the star the higher probability that it transits

60. Spectroscopic Transits: The Rossiter-McClaughlin Effect 1 1 0 +v –v 2 3 4 2 3 4 The R-M effect occurs in eclipsing systems when the companion crosses in front of the star. This creates a distortion in the normal radial velocity of the star. This occurs at point 2 in the orbit.

61. From Holger Lehmann The Rossiter-McLaughlin Effect in an Eclipsing Binary

62. Curves show Radial Velocity after removing the binary orbital motion The effect was discovered in 1924 independently by Rossiter and McClaughlin

63. The Rossiter-McLaughlin Effect or „Rotation Effect“ For rapidly rotating stars you can „see“ the planet in the spectral line

64. For stars whose spectral line profiles are dominated by rotational broadening there is a one to one mapping between location on the star and location in the line profile: V = –V rot V = +V rot V = 0

65. For slowly rotationg stars you do not see the distortion, but you measure a radial velocity displacement due to the distortion. A „Doppler Image“ of a Planet

66. The Rossiter-McClaughlin Effect –v–v +v 0 As the companion crosses the star the observed radial velocity goes from + to – (as the planet moves towards you the star is moving away). The companion covers part of the star that is rotating towards you. You see more possitive velocities from the receeding portion of the star) you thus see a displacement to + RV. –v–v +v When the companion covers the receeding portion of the star, you see more negatve velocities of the star rotating towards you. You thus see a displacement to negative RV.

67. Amplitude of the R-M effect: A RV =  m s –1 Note: 1. The Magnitude of the R-M effect depends on the radius of the planet and not its mass. 2. The R-M effect is proportional to the rotational velocity of the star. If the star has little rotation, it will not show a R-M effect. r R Jup () 2 R RסּRסּ ( ) –2–2 VsVs 5 km s –1 () A RV is amplitude after removal of orbital mostion V s is rotational velocity of star in km s–1 r is radius of planet in Jupiter radii R is stellar radius in solar radii

68. The Rossiter-McClaughlin Effect What can the RM effect tell you? 1. The inclination of „impact parameter“ –v–v +v –v–v Shorter duration and smaller amplitude

69. The Rossiter-McClaughlin Effect What can the RM effect tell you? 2. Is the companion orbit in the same direction as the rotation of the star? –v–v +v –v–v

70. What can the RM effect tell you? 3. Are the spin axes aligned? Orbital plane

71. TrES-1

72. So far most transiting planets for which an RM effect has been measured has shown prograde orbits What about misalignment of the spin axis? Results from the Rossiter-McClaughlin Effect

73. HD 147506 Best candidate for misalignment is HD 147506 because of the high eccentricity

75. Two possible explanations for the high eccentricities seen in exoplanet orbits: Scattering by multiple giant planets Kozai mechanism On the Origin of the High Eccentricities

76. Planet-Planet Interactions Initially you have two giant planets in circular orbits These interact gravitationally. One is ejected and the remaining planet is in an eccentric orbit

77. Recall that there are no massive planets in circular orbits This mechanism has been invoked to explain the „massive eccentrics“

78. Kozai Mechanism Two stars are in long period orbits around each other. A planet is in a shorter period orbit around one star. If the orbit of the planet is inclined, the outer planet can „pump up“ the eccentricity of the planet. Planets can go from circular to eccentric orbits. This was first investigated by Kozai who showed that satellites in orbit around the Earth can have their orbital eccentricity changed by the gravitational influence of the Moon

79. Kozai Mechanism The Kozai mechanism has been used to explain the high orbital eccentricity of 16 Cyg B, a planet in a binary system

80. Winn et al. 2007: HD 147506b (alias HAT-P-2b) If either mechanism is at work, then we should expect that planets in eccentric orbits not have the spin axis aligned with the stellar rotation. This can be checked with transiting planets in eccentric orbits Spin axes are aligned within 14 degrees (error of measurement). No support for Kozai mechanism or scattering

81. What about HD 17156? Narita et al. (2007) reported a large (62 ± 25 degree) misalignment between planet orbit and star spin axes!

82. Cochran et al. 2008: = 9.3 ± 9.3 degrees → No misalignment!

83. Fabricky & Winn, 2009, ApJ, 696, 1230

84. XO-3-b

85. Hebrard et al. 2008 = 70 degrees

86. Winn et al. (2009) recent R-M measurements for X0-3 = 37 degrees

87. Possible inclination changes in TrEs-2 Evidence that transit duration has decreased by 3.2 minutes. This might be caused by inclination changes induced by a third body The biggest effect should be for grazing transits

88. Transit Timing Variations (TTVs) Changes in the expected times of transits are indications of other bodies in the system: Another (outer) planet that influences the center of mass motion of the star and perturbs the transiting planets orbit A moon that influences the planet‘s center of mass Transit delayed from previous time

89. TTVs: you need lots of transits!

90. Bean et al. 2009 Currently there is no evidence for TTVs in transiting planets, probably due to the difficulty in measuring these: these are too small.

91. 1. 59 Transiting planets have been discovered most from the ground. 2.Most have radii that are larger than Jupiter (inflated) 3. Smallest has radius of Neptune (wait for CoRoT talks) 4.Mean density gives us our first estimate of the internal structure 5. R-M effect can tell us about spin alignment. Most transiting planets have aligned orbits 6. Transit searches may have a less biased sample than radial velocity searches Summary