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Statistical patterns in ground-based transit surveys

Statistical patterns in ground-based transit surveys. Andrew Collier Cameron University of St Andrews. Super WASP Wide Angle Search for Planets. TrES : The Trans- atlantic Exoplanet Survey. Ground-based transit surveys. STARE. PSST. SLEUTH. XO. HAT. HAT-S. WASP.

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Statistical patterns in ground-based transit surveys

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  1. Statistical patterns in ground-based transit surveys • Andrew Collier Cameron • University of St Andrews SuperWASP Wide Angle Search for Planets TrES: The Trans-atlanticExoplanet Survey

  2. Ground-based transit surveys STARE PSST SLEUTH XO HAT HAT-S WASP

  3. Geographical distribution PSST(1) SLEUTH(1) HAT(1) HAT(4) WASP-N(8) XO(2) HAT(2) STARE(1) HAT-S(4) HAT-S(4) HAT-S(4) WASP-S(8)

  4. WASP observations per star • Typically ~ 5000 obs spanning 120N per season

  5. Bright (V<14) Transiting planets

  6. Red noise and detection threshold Smith, A M S et al, 2006 80 nights 80 nights 130 nights 130 nights

  7. Orbital period distribution Cumulative fraction Orbital period in days

  8. Host-star apparent magnitudes Cumulative fraction V magnitude

  9. Host-star effective temperatures • Bentley 2009, PhD thesis, Univ.of Keele All dwarfs in WASP archive

  10. Smaller stars yield smaller planets

  11. Super-Jupiters & BDs With thanks to MagaliDeleuil

  12. It isn’t a planet until you’ve weighed it • Magnitude range matches capabilities of RV spectrometers on 2-10m telescopes: • OGLE: VLT8.2m/UVES • TrES: Keck10m/HIRES • HAT: OHP1.93/SOPHIE; SUBARU8.4/HDS • XO: McDonald2.7, HET11.0 • WASP-N: OHP1.93/SOPHIE, NOT2.4/FIES • WASP-S: Swiss Euler 1.2m, ESO3.6/HARPS

  13. Planetary mass-radius relation

  14. Host-star Metallicities Frequency [Fe/H]

  15. Fressin et al (2007)

  16. Fressin et al (2007)

  17. Gas-giant mass-radius relation

  18. Separation - Mass relation • Mazeh, Zucker & Pont (2005) • Low-mass gas giants avoid small separations. • Ice-giants and super-Earths behave differently. • Symbol size denotes planet radius.

  19. Irradiation - Mass relation • Low-mass gas giants avoid strong irradiation. • Inflated planets found close to boundary. • Symbol size denotes planet radius. • Cf. Baraffe et al 2004 • Evaporation/expansion • Critical mass at radius a

  20. Irradiation-radius relation • Guillot & Showman 2002 • Fressin et al 2007 • Symbol size denotes planet mass range: • Low: 0.0 to 0.5 MJ • Mid: 0.5 to 2.0 MJ • High: Above 2.0 MJ

  21. Irradiation-radius relation • Most apparent in restricted mass ranges. • Enoch et al 2010 • 0.1 MJ < Mp < 0.6 MJ • MNRAS, in press • arXiv/1009.5917

  22. Tidal heating? • Circles: WASP planets, RV only • Dots: WASP planets with low Lucy-Sweeney (1971) false-alarm probability. • Triangles: Upper limits on e cos w from secondary-eclipse timing.

  23. Eccentricity versus K • Poorly-constrained orbits yield spurious eccentricities. • Lucy & Sweeney (1971) • Laughlin et al (2005) • Ford (2006)

  24. Why the prior increases with e e sin w ecosw

  25. Circularization timescale • WASP planets with significant eccentricity detections • Masses (MJ) in parentheses • Triangles: Upper limits on e cos w from secondary-eclipse timing. • Mostly less massive. • Cf. Goldreich & Soter (1966):

  26. Spin-orbit misalignments • Measured via Rossiter-McLaughlin effect. • Winn et al (assorted) • Misaligned and retrograde planets surprisingly common: scattering/Kozai/tides? • Triaud et al (2010); Wu & Murray 2003; Fabrycky & Tremaine 2007 • Aligned planets more prevalent around cool stars? • Winn et al 2010 • See talks by Josh Winn, Amaury Triaud (Wednesday)

  27. Falling planets? • Levrard et al 2008: • Close-in planets lack sufficient orbital angular momentum to synchronize stellar spin to orbit. • Tidal evolution leads to spiral-in. • See talk on WASP-18b and WASP-19b by David Brown, Thursday.

  28. Conclusions • Ground-based surveys address the hottest gas-giant planets orbiting bright, ~solar-type stars. • Mass-radius relation • Low.mass planets: composition sequence • High-mass planets: radius anomaly appears to be primarily an irradiation effect. • Orbital eccentricity distribution shows parameter dependences expected from circularization timescale. • Spin-orbit alignment more common around stars with outer convective zones. • Some of the closest-orbiting gas giants may spiral into their host stars before the end of the main sequence.

  29. Host-star rotation - I Schlaufman 2010, ApJ 719, 602

  30. Eccentricity, mass, obliquity • 21 planets with projected obliquity measurements • 15 aligned • 3 inclined, prograde • 5 inclined, retrograde Assorted works by Queloz, Winn, Wolf, Narita, Johnson, Bouchy, Hebrard, Cochran, Triaud, … Planet mass in Mj Orbital eccentricity

  31. Host-star rotation - II Schlaufman 2010, ApJ 719, 602

  32. Stellar rotation and tidal evolution • For aligned systems: • Time to tidal spiral-in: • Hut 1980, 1981 • Dobbs-Dixon et al 2004 • Levrard et al 2009 • Main-sequence lifetime:

  33. Short life expectancies? • For tidal dissipation factor Q=106: • Massive, eccentric planets have pseudo-synchronised host stars HD 80606b CoRoT-3b HD 17156b W* / Worb HAT-P-2b XO-3b WASP-18b tremain / tMS

  34. Or inefficient tidal dissipation? • For tidal dissipation factor Q=108: HD 80606b CoRoT-3b HD 17156b W* / Worb HAT-P-2b XO-3b WASP-18b tremain / tMS

  35. Tidal evolution: WASP-18b 1 Gyr 5 Gyr 2 Gyr • Using tidal evolution prescription of Dobbs-Dixon, Lin & Mardling (2004) 63 Myr WASP-18 Hellier et al 2009 Hellier et al 2009

  36. Small stars yield small planets • HAT/WASP/XO/TrES: median host-star Teff is close to solar. • Small planets easiest to detect around smaller stars. • Survey volume contains few stars cooler than ~4600K. • Long data trains and careful photometric extraction needed. Cumulative probability Planet radius in RJup GJ436b HAT-P-11b Host Star Teff

  37. Summary • WASP detection thresholds comparable to HAT, TrES, XO. • Bayesian candidate selection cuts down astrophysical false positives. • On-off photometry eliminates blended EBs • Still room for improvement: • Lens temperature • DIA • Multi-season BLS. • 16 planets found so far • 8 per hemisphere • Interesting trends emerging!

  38. SuperWASP Wide Angle Search for Planets S. Aigrain (Cambridge -> Exeter) D. Anderson (Keele) S. Bentley (Keele) A. Carter (Open University) D.J. Christian (Belfast) W.I. Clarkson (Open University -> STScI) A. Collier Cameron (St Andrews) B. Enoch (Open University-> St Andrews) N.Gibson (Belfast) C.A. Haswell (Open University) L. Hebb (St Andrews) C. Hellier (Keele) K. Horne (St Andrews) J. Irwin (Cambridge -> CfA Harvard) Y. Joshi (Belfast) S.R. Kane (St Andrews -> Caltech) F.P. Keenan (Belfast) T.A. Lister (St Andrews/Keele -> LCOGT) P. Maxted (Keele) I. McDonald (Keele) A.J. Norton (Open University) J. Osborne (Leicester) N. Parley (Open University) D. Pollacco (Belfast) R. Ryans (Belfast) E. Simpson (Belfast) I. Skillen (ING) B. Smalley (Keele) A.M.S. Smith (St Andrews) I. Todd (Belfast) R.A. Street (Belfast -> LCOGT) R.G. West (Leicester) D.M. Wilson (Keele) P.J. Wheatley (Leicester -> Warwick) With: F. Bouchy (IAP) G. Hébrard (IAP) F. Pont (Geneva->Exeter) B. Loeillet (Marseille) M. Gillon (Geneva) M. Mayor (Geneva) C. Moutou (Marseille) F. Pepe (Geneva) D. Queloz (Geneva) A.M.H.J. Triaud (St Andrews -> Geneva) S. Udry (Geneva)

  39. WASP: stellar number density

  40. RMS scatter RMS scatter (real data, 2.5-hr bins) RMS scatter (white noise, 2.5-hr bins)) Systematics and red noise • Systematics: • Secondary extinction • Temperature-dependent focus • Sky brightness-dependent bias in background subtraction • SysRem: Tamuz et al 2005 • TFA: Kovacs et al 2005 • Red noise: • Pont et al 2006 • Smith et al 2006 RMS scatter RMS scatter (real data, 2.5-hr bins) RMS scatter (white noise, 2.5-hr bins))

  41. Planet-catch simulations • Smith, A M S et al, 2006 • Besançon model: • V, Teff, [Fe/H] • P(planet) = 0.03x102.0[Fe/H] • Fischer & Valenti 2005 • Linear CDF in log a • Transit probability ~ R*/a • Inject fake Jupiter-sized planet transits into real WASP light curves.

  42. Red noise and planet catch Season 1 Season 2

  43. Sensitivity • Transit depth threshold: • 0.01 mag@V=11 • 0.015 mag@V=12

  44. Measurable parameters • Winn 2008, IAU Symp. 253

  45. Measurable parameters • Winn 2008, IAU Symp. 253

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