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