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SUMMARY:Measuring orbital eccentricity using asteroseismology: small plane
 ts in Kepler multi-planet systems have low eccentricities - Vincent van Ey
 len (Aarhus)
DTSTART:20150506T153000Z
DTEND:20150506T163000Z
UID:TALK58635@talks.cam.ac.uk
CONTACT:Dr B.-O. Demory
DESCRIPTION:Solar system planets move on almost circular orbits. In strong
  contrast\, many massive gas giant exoplanets travel on highly elliptical 
 orbits\, whereas the shape of the orbits of smaller\, more terrestrial\, e
 xoplanets remained largely elusive. Knowing the eccentricity distribution 
 in systems of small planets would be important as it holds information abo
 ut the planet’s formation and evolution\, and influences its habitabilit
 y. I present measurements made using photometry from the Kepler satellite 
 and utilizing a method relying on Kepler’s second law\, which relates th
 e duration of a planetary transit to its orbital eccentricity\, if the ste
 llar density is known. Our sample consists of 28 bright stars with precise
  asteroseismic density measurements. These stars host 74 planets with an a
 verage radius of 2.6 Rearth . We find that the eccentricity of planets in 
 Kepler multi-planet systems is low and can be described by a Rayleigh dist
 ribution with s = 0.049 ± 0.013. This is in full agreement with solar sys
 tem eccentricities\, but in contrast to the eccentricity distributions pre
 viously derived for exoplanets from radial velocity studies. Our findings 
 are helpful in identifying which planets are habitable because the locatio
 n of the habitable zone depends on eccentricity\, and to determine occurre
 nce rates inferred for these planets because planets on circular orbits ar
 e less likely to transit. For measuring eccentricity it is crucial to dete
 ct and remove Transit Timing Variations (TTVs)\, and we present some previ
 ously unreported TTVs. Finally transit durations help distinguish between 
 false positives and true planets and we use our measurements to confirm si
 x new exoplanets.
LOCATION:Martin Ryle Seminar Room\, Kavli Institute
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