Transcript Slide 1
Characterizing Extrasolar Planets from their Transit Lightcurves Oblateness, Rings, Moons Jason W. Barnes Assistant Professor Department of Physics University of Idaho ECE Seminar 2008 December 11 Moscow, ID Transit (if only they looked like this!) Transit Lightcurves Transit schematic To first order (providing a surprisingly good description), lightcurve determines l – transit duration d – transit depth w – ingress/egress duration h – curvature from limb darkening these 4 measurables determine 4 transit parameters: Rp – planet radius R* – star radius b – transit impact parameter c1 – stellar limb darkening (Brown et al., 2001) Transiting Planets Discovered So Far The Kepler Mission: A Search for Habitable Planets Kepler Field of View Kepler Field of View Kepler Focal Plane Assembly Kepler Orbit and Quarterly Rolls Kepler Focal Plane Assembly Kepler Planet Discovery Pipeline New data arrive every 30 days. 1. Perform photometry 2. De-trend time series 3. Whiten 4. Fold data at various test periods; hunt for transits using notched filter correlation 5. Rule out false-positives (hard) Characterizing Transit Lightcurves: Oblateness Detectability of Non-Zero Obliquity Planet Time from Mid-Transit (hours) Seager & Hui (2002); Barnes & Fortney (2003) Detectability of Zero-Obliquity Planet Time from Mid-Transit (hours) Barnes & Fortney (2003) Deriving Rotation Rate from Oblateness Barnes & Fortney (2003) What Does Rotation Tell Us About Planets? Increasing semimajor axis Bears fingerprints of formation Reveals degree of tidal influence & Q Could constrain tidal dissipation mechanism 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 Uranus HST Neptune Voyager 2 Detecting Extrasolar Moons 2 methods: Sartoretti & Schneider (1999) 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 Simultaneous fit for timing, direct transit maximum moon parameters to be fit: M, r, a, q, e, i, j, f Kepler Characterizing Transiting Planets Kepler will find Earth-sized planets. In doing so, Kepler will also incidentally discover ~100 transiting giant planets Oblateness – result of planet's spin If nonzero obliquity, induces lightcurve asymmetry For zero obliquity, detectabilities are low If detected can allow inference of planet's rotation rate Rings Induce evident transit signatures, for large Saturn-like systems Can help constrain the origin and evolution of all ring systems Moons Revealed by both timing and direct moon transit Can find habitable moons and constrain planetary parameters