Characterizing Planets from their Transit Lightcurves Jason W. Barnes NASA Postdoctoral Program Fellow NASA Ames Research Center Advisor: William J. Borucki Kepler Science Working Group Meeting Ball Aerospace Boulder, CO 2007 November 8 Oblateness, Rings, Moons

Transit schematic To first order (providing a surprisingly good description), lightcurve determines l – transit duration d – transit depth w – ingress/egress duration  – curvature from limb darkening these 4 measurables determine 4 transit parameters: R p – planet radius R * – star radius b – transit impact parameter c 1 – stellar limb darkening (Brown et al., 2001)

Seager & Hui (2002); Barnes & Fortney (2003) Time from Mid-Transit (hours) Detectability of Non-Zero Obliquity Planet

Time from Mid-Transit (hours) Detectability of Zero-Obliquity Planet Barnes & Fortney (2003)

Deriving Rotation Rate from Oblateness Barnes & Fortney (2003)

What Does Rotation Tell Us About Planets? Bears fingerprints of formation Reveals degree of tidal influence & Q Could constrain tidal dissipation mechanism Increasing semimajor axis Barnes & Fortney (2003)

Detectability of Large, Saturn-Like Ring Systems Barnes & Fortney (2004)

Diffraction Can Reveal Ring Particle Size Barnes & Fortney (2004)

Why Would Extrasolar Rings Matter? Can help to constrain ring formation conditions Chemistry Could empirically address age of ring systems in general Possible Saturn implications Will add to the ring menagerie; what ring architechtures are possible? Are ring systems normal, or is Saturn special? Jupiter Cassini / ISS Saturn Cassini / VIMS Uranu s HST Neptune Voyager 2

Sartoretti & Schneider (1999) Detecting Extrasolar Moons 2 methods: Direct transit Transit timing Brown, Charbonneau, Gilliland, Noyes, & Brown (2001) placed upper limits on moons of HD209458b from HST STIS photometry – 1.2 R ⊕ and 3 M ⊕

Algorithm Under Development for Kepler Simultaneous fit for timing, direct transit maximum moon parameters to be fit: M, , a,  e, i, 

Science from Moon Detections Alternate reservoir of rocky “planets” HD28185b, 55 Cancri f Direct transit & timing together can set density, chemistry of the satellite Can infer planet axis orientation if moon orbits equatorially Outstanding Issues Tides induce loss of moons for inner planets; will outer planets have enough transits for timing? How to differentiate moon-induced timing variations from that caused by other planets in the system? Computation complexity Period aliasing an issue?

Effects on Kepler Operations Nominally none – oblateness, ring, and moon searches can be done with nominal transit search data 1-minute cadence for short-period planets critical, but already planned to be obtained Best candidates for fortuitous one-time outer giant planets are same as those for Earths – high S/N and time-resolution is better.