Transiting Extrasolar Planets

Transcription

1 Transiting Extrasolar Planets Recent Progress, XO Survey, and the Future Christopher J. Burke

2 Solar System Has Predominately Circular Orbits Top View Side View

3 Planet Formation NASA/JPL-Caltech/R. Hurt (SSC)

4 Exceptions Non-circular Eccentricity Pluto Sedna Nasa/Caltech Courtesy of Windows to the Universe,

5 ~200 Extrasolar Planets

6 >7% stars have Jupiter mass planets within 5 AU 1.2% stars have Hot Jupiter planets Most planets have a>1 AU Metallicity Correlation Fischer & Valenti 2005

7 Multi-planet systems common (>30%) Wright et al. (2006) Low mass planets more common than high mass planets. NASA/JPL-Caltech/T. Pyle (SSC) 5.5 Earth mass planet Beaulieu et al. (2006)

8 Think Quest How do you detect planets? Radial Velocity Technique Doppler Shifted Light Only Measure Planet Mass

9 Extrasolar Planet Detection Transit Technique Measure Radius!! flux time Δf = (R p /R * ) 2 ~1%

10 Charbonneau et al. 2006, Brown et al. 2001

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12 Core Dominated 70 M earth core Sato et al. (2005) & Fortney et al. (2005) Difficult to explain Charbonneau et al Inflated Radius

13 What do we learn from Transiting Planets? Highly accurate radii Stellar limb darkening Dan Bruton

14 HD b Knutson et al. (2006)

15 What do we learn from Transiting Planets? Highly accurate planet radii Stellar limb darkening Characterize planet atmosphere Transmission spectroscopy Na, H, C, O detection HD Charbonneau et al. (2002), Vidal-Madjar (2003, 2004)

16 Out of Transit Compare Spectra In Transit Vidal-Madjar (2003)

17 Vidal-Madjar (2003)

18 What do we learn from Transiting Planets? Highly accurate planet radii Stellar limb darkening Characterize planet atmosphere Phased light curve optical

19 Reflected Light Albedo <0.25 Rowe et al. (2006) will soon reach ~0.1 limits Hot Jupiter planets are dark!

20 What do we learn from Transiting Planets? Highly accurate planet radii Stellar limb darkening Characterize planet atmosphere Secondary Eclipse IR Test planet atmosphere models

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22 NASA/JPL-Caltech/R. Hurt (SSC)

23 Constrain atmosphere metallicity, clouds, redistribution of heat, perhaps CO & H 2 O Disentagling these effects may be difficult Burrows et al. (2006)

24 Motivated to find bright transiting planets XO Transit Survey PI Peter McCullough Jeff Valenti Ken Janes, Boston U Jim Heasley, U of Hawaii Chris Johns-Krull, Rice U Extended Team Professionals & Amateurs Ron Bissinger, CA Mike Fleenor, TN Cindy Foote, UT Enrique Garcia, Spain Bruce Gary, AZ Paul Howell, ME Franco Malia, Italy Gianluca Masi, Italy Tonny Vanmunster, Belgium

25 Haleakala, Maui

26 Baker Nunn Observatory 1957 Built to track satellites in particular Sputnik

27 Today houses XO

28 10 cm aperture Every 10 min 7.2 o x 63 o strip

29 Why have so few transits been found? Only 1.2% stars have Hot Jupiter planets The probability for a Hot Jupiter to transit ~10% Most stars are too big (sub-giant or giant) In magnitude limited survey only 10% of stars are dwarfs Gould & Morgan (2003) There are many objects that mimic a transit signal

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31 Transit Imposters Transit surveys yield 10/1 false positives Dwarf star eclipsing a subgiant/giant Grazing eclipsing binary Triple star / blend diluted deep eclipse Brown dwarfs

32 Transit Imposters

33 Brown dwarf same radius as planet! 96 M Jup Radial Velocity Followup Required!

34 How does XO deal with imposters Stellar spectral type estimate Photometric catalogs - Tycho, 2MASS, TASS Transit duration, depth, and period consistent with a planet orbiting the estimated stellar spectral type

35 Discriminate dwarfs from giants Closer stars Higher Proper Motion DSS1 DSS2 2MASS NASA/IPAC Infrared Science Archive

36 XO's Extended Team

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38 Blending

39 Triple Stars

40 XO has time on the Hobby-Eberly Telescope for precision RV Confirmed XO-1b as a bona fide planet

41 Future of Extrasolar Planets HARPS now achieves 20 cm/s RV stability over several days Pont priv. comm. (2006) ESO La Silla 3.6m

42 Space Based Transit Searches COROT Launched Dec cm primary 2.5 year duration 150 day continuous

43 Space Based Transit Searches KEPLER Nov m primary 4 year duration fully continuous 42 CCDs to fill 1.2 o diameter FOV 100,000 stars V<15.0

44 Precision Transit Timing Sensitive to moons, rings, stellar spots Can detect Earth mass planets in resonance XO Future XO-2b, XO-3b, XO-4b,... Expansion to 3+ mounts in 2007