leslie rogers hubble fellow california institute of technology [email protected] kepler science...
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Leslie RogersHubble Fellow
California Institute of [email protected]
Kepler Science Conference II – November 4, 2013
Glimpsing the Compositions of Sub-Neptune-Size Exoplanets
Mp <124 M
Porb = 290 days
Borucki et al. (2012)Figure Credit: NASA/Ames/JPL-Caltech
Rocky
Volatile Rich?OR
Kepler-22b: Rp = 2.4 R
Six Years Ago
100% Silicate100% H2O
100% Iron
Seager et al. (2007) M-R Relations
Non-Kepler Planets
100% Silicate100% H2O
100% Iron
Seager et al. (2007) M-R Relations
Kepler Planets
100% Silicate100% H2O
100% Iron
Seager et al. (2007) M-R Relations
Masses & Radii of 49 Planets from KeplerMarcy et al. (2013) submitted
• Radial velocity follow-up observations of 22 sub-Neptune-size KOIs with Keck-HIRES
• Selection Criteria:– Planet candidates smaller than 4 REarth
– Predicted RV amplitude detectable (K > 1m s-1)– Stellar Properties: Kp < 13.5, Teff<6100K, vsini < 5 km s-1
• Results: – 42 Transiting Planets, 7 Non-Transiting planets in 22 planetary
systems– 16 transiting planets have strong mass measurements, rest have
marginal RV detections or mass upper limits
Kepler Planets
100% Silicate100% H2O
100% Iron
Seager et al. (2007) M-R Relations
New Kepler Planet Masses from Keck RVs
100% Silicate100% H2O
100% Iron
Seager et al. (2007) M-R Relations Marcy et al. (in prep)
New Kepler Planet Masses from Keck RVs
Which Planets Are Rocky?
Which Planets Are Rocky?
Which Planets Are Rocky?
Non-Rocky
Which Planets Are Rocky?
Potentially Rocky
Non-Rocky
Smaller Planets are DenserPotentially Rocky
Non-Rocky
How does the Fraction of Planets Dense Enough to be Rocky vary with Rp?
Model:
Mass
Radius
Mass
Radius
Simplest Model for frocky (Rp): Step Function
frocky(Rp) (Fraction of planets that are rocky)
1 model parameter:Rocky/Non-Rocky Radius Threshold
Step-Function Model:Radius Upper Limit for Rocky Planets
Rogers 2014 (submitted)
Step-Function Model:Radius Upper Limit for Rocky Planets
Median 1.48 +0.04
-0.05 R
Rogers 2014 (submitted)
Step-Function Model:Radius Upper Limit for Rocky Planets
Median 1.48 +0.04
-0.05 R
95% Confidence Upper Bound 1.59 +0.18
-0.05 R
Rogers 2014 (submitted)
Model #2 for frocky (Rp): Linear Transition
frocky(Rp) (Fraction of planets that are rocky)
2 model parameters:Rmid transition midpointDR transition width
Linear Transition Model:Radius Limits for Rocky / Non-Rocky Planets
R50% rocky = 1.48 +0.16
-0.50 R
< 1.61 R (95% conf.)
Rogers 2014 (submitted)
Linear Transition Model:Posterior Distribution for frocky(Rp)
p(frocky |R
p , da
ta)
Rogers 2014 (submitted)
Bayesian Evidence Prefers Simpler 1-parameter Step Function Model
Model 1: Step Function1 parameter
Model 2: Linear Transition2 parameters
Preferred E 1 ~ 5 E 2
Figure Credit: NASA/Ames/JPL-Caltech
Main Take Away: Most planets larger than 1.6 R are not Rocky.
Rocky
Volatile Rich?OR
Kepler-22b(Rp = 2.4 R):
Leslie RogersHubble Fellow
California Institute of [email protected]
Extra Slides
Kepler Science Conference II – November 4, 2013
Incident Flux Dependent frocky?Non-Rocky
Potentially Rocky
100 101 104102 103
Smaller Planets are DenserPotentially Rocky
Non-Rocky
Linear Transition Model:Predictive Distribution of frocky(Rp)
Non-Rocky
Potentially Rocky
100% Silicate
Probability a Planet is Sufficiently Dense to be Rocky, procky
Seager et al. (2007) M-R Relations
Planets Detected both Dynamically and in Transit are Valuable!
Stellar Wobble Transits
Planet Mass Planet Radius
Planet Density
Super-Earth and Sub-Neptune Planets
Earth1 M
1 R
Uranus & Neptune15 M
4 R
Super-Earth and Sub-Neptune Planets
Earth1 M
1 R
Uranus & Neptune15 M
4 R
1.6 R