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

Solar System Has Predominately Circular Orbits Top View Side View

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

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

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

Charbonneau et al. 2006, Brown et al. 2001

Core Dominated Inflated Radius 70 M earth core Sato et al. (2005) & Fortney et al. (2005) Difficult to explain Charbonneau et al. 2006

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

HD b Knutson et al. (2006)

● 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) What do we learn from Transiting Planets?

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

● Highly accurate planet radii ● Stellar limb darkening ● Characterize planet atmosphere Phased light curve – optical What do we learn from Transiting 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 – IR Test planet atmosphere models What do we learn from Transiting Planets?

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

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

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

Haleakala, Maui

Baker Nunn Observatory 1957 Built to track satellites in particular Sputnik

Today houses XO

Every 10 min 7.2 o x 63 o 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 mimic a transit signal

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

Transit Imposters

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

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

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

XO's Extended Team

Blending

Triple Stars

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

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

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

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

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