Transiting Extrasolar Planets Recent Progress, XO Survey, and the Future Christopher J. Burke
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Transiting Extrasolar PlanetsRecent Progress, XO Survey, and the Future
Christopher J. Burke
Solar SystemHas Predominately
Circular Orbits
Top ViewSide View
Planet Formation
NASA/JPL-Caltech/R. Hurt (SSC)
ExceptionsNon-circularEccentricity
PlutoSedna
Nasa/Caltech Courtesy of Windows to the Universe, http://www.windows.ucar.edu
~200 Extrasolar Planets
● >7% stars have Jupiter mass planets within 5 AU● 1.2% stars have Hot Jupiter planets● Most planets have a>1 AU
Fischer & Valenti 2005
Metallicity Correlation
● Multi-planet systems common (>30%)Wright et al. (2006)
● Low mass planets more common than high mass planets.
●5.5 Earth mass planet Beaulieu et al. (2006)
NASA/JPL-Caltech/T. Pyle (SSC)
How do you detect planets?Radial Velocity Technique
Only Measure Planet Mass
Doppler Shifted Light
©Think Quest
flux
time
Transit TechniqueExtrasolar Planet Detection
Δf = (Rp/R*)2 ~1%
Measure Radius!!
Charbonneau et al. 2006, Brown et al. 2001
Core Dominated
Inflated Radius
70 Mearth coreSato et al. (2005) & Fortney et al. (2005)
Difficult to explain
Charbonneau et al. 2006
● Highly accurate radii● Stellar limb darkening
What do we learn fromTransiting Planets?
Dan Bruton
HD 209458bKnutson et al. (2006)
● Highly accurate planet radii● Stellar limb darkening● Characterize planet atmosphere
Transmission spectroscopyNa, H, C, O detection HD 209458Charbonneau et al. (2002), Vidal-Madjar (2003, 2004)
What do we learn fromTransiting Planets?
Compare SpectraOut of Transit
In Transit Vidal-Madjar (2003)
Vidal-Madjar (2003)
● Highly accurate planet radii● Stellar limb darkening● Characterize planet atmosphere
Phased light curve – optical
What do we learn fromTransiting Planets?
Albedo <0.25 Rowe et al. (2006)will soon reach ~0.1 limits
Hot Jupiter planets are dark!
Reflected Light
● Highly accurate planet radii● Stellar limb darkening● Characterize planet atmosphere
Secondary Eclipse – IRTest planet atmosphere models
What do we learn fromTransiting Planets?
NASA/JPL-Caltech/R. Hurt (SSC)
Constrain atmosphere metallicity, clouds, redistribution of heat, perhaps CO & H2O
Disentagling these effects may be difficult
Burrows et al. (2006)
Motivated to find bright transiting planets
XO Transit SurveyPI Peter McCullough
Jeff ValentiKen Janes, Boston U
Jim Heasley, U of HawaiiChris Johns-Krull, Rice U
Extended Team Professionals & “Amateurs”
Ron Bissinger, CAMike Fleenor, TNCindy Foote, UTEnrique Garcia, SpainBruce Gary, AZ
Paul Howell, MEFranco Malia, Italy Gianluca Masi, ItalyTonny Vanmunster, Belgium
Haleakala, Maui
Baker Nunn Observatory 1957Built to track satellitesin particular Sputnik
www.ifa.hawaii.edu/users/steiger/post_cook.htm
Today houses XO
Every 10 min7.2o x 63o strip
10 cm aperture
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 mimica transit signal
Transit ImpostersTransit surveys yield 10/1 false positives
● Dwarf star eclipsing a subgiant/giant● Grazing eclipsing binary● Triple star / blend diluted deep eclipse● Brown dwarfs
Transit Imposters
96 MJup
Brown dwarf same radiusas planet!
Radial Velocity Followup Required!
How does XO deal with imposters
Stellar spectral type estimate Photometric catalogs - Tycho, 2MASS, TASS
Transit duration, depth, and periodconsistent with a planet orbiting the estimated stellar spectral type
Closer stars Higher Proper Motion
1955 1993 2000
NASA/IPAC Infrared Science Archive
DSS1 DSS2 2MASS
Discriminate dwarfs from giants
XO's Extended Team
Blending
Triple Stars
XO has timeon the Hobby-EberlyTelescopefor precisionRV
ConfirmedXO-1bas a bona fideplanet
Future of Extrasolar Planets
HARPS now achieves 20 cm/sRV stability over several days
ESO La Silla 3.6m
Pont priv. comm. (2006)
Space Based Transit SearchesCOROT – Launched Dec. 26
27cm primary2.5 year duration
150 day continuous
KEPLER – Nov. 20081.4m primary4 year duration fully continuous42 CCDs to fill 1.2o diameter FOV 100,000 stars V<15.0
Space Based Transit Searches
Precision Transit Timing
Sensitive to moons, rings, stellar spotsCan detect Earth mass planets in resonance
XO Future
XO-2b, XO-3b, XO-4b,...Expansion to 3+ mounts in 2007
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