WARM SPITZER PHASE
VARIATIONS OF WASP-12B:
DEFYING PREDICTIONS
Nick Cowan
with Louis Shekhtman (NU undergrad)
Machalek, Croll, Burrows, Deming
CIERA Postdoctoral Fellow
Northwestern University
September 15th 2011
WASP-12b: a Tortured World
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~1 day orbit: Oblate Planet
Tidally Warped: Prolate Planet
Tday≈3000 K: MHD Effects
Big Rp, small a:
Roche-Lobe Overflow
• Accretion on Star/ Bow Shock
• Peculiar Eclipse Depths:
High C/O ratio
QuickTime™ and a
decompressor
are needed to see this picture.
(Hebb et al. 2009; Ragozzine & Wolf 2009; Li
et al. 2010; Lai et al. 2011; Leconte et al.
2011; Fossati et al. 2010; Vidotto et al. 2010;
Llama et al. 2011; Madhusudhan et al. 2011)
Check Out These Posters:
Li et al. (2010)
Sept 15, 2011
Crossfield 40.08
Petigura 33.03
Moses 40.04
Nick Cowan's Talk at ESS II
2
Thermal + Ellipsoidal Variations
Optical Light Observations
• Reflected Light Dominates Phases
• Star’s Shape Dominates Geometry
Infrared Observations
• Thermal Emission Dominates Phases
• Planet’s Shape Dominates Geometry
Brightness Phases:
Planet Light
Geometrical Phases:
Projected Area
HAT-P-7b as seen by Kepler
(Welsh et al. 2010)
Sept 15, 2011
Nick Cowan's Talk at ESS II
3
Raw WASP-12b Photometry
Phase Function
Eclipse
Eclipse
3.6 micron
4.5 micron
Transit
Intra-pixel sensitivity variations
are the dominant systematic
1. Gaussian Decorrelation (Ballard et al. 2010)
2. Polynomial in Centroid x and y
Sept 15, 2011
Nick Cowan's Talk at ESS II
4
WASP-12b at 3.6 micron
Atherm/<Fp> = 0.9(3)
Sept 15, 2011
Nick Cowan's Talk at ESS II
max = -53(7)°
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Increasing Heat Capacity
1) Decreases Thermal Phase Amplitude
2) Increases Hot Spot Offset
Midnight
SOP
Sept 15, 2011
Dusk SOP
Nick Cowan's Talk at ESS II
Noon
SOP
Cowan & Agol (2011a)
What Planets Are Supposed To Do
Dawn
SOP
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WASP-12b at 3.6 micron
Atherm/<Fp> = 0.9(3)
max = -53(7)°
Aellips = 2(2)x10-4
Sept 15, 2011
Nick Cowan's Talk at ESS II
7
WASP-12b at 4.5 micron
Atherm/<Fp> = 0.7(1)
max = -16(4)°
Consistent with Cowan & Agol (2011a) Toy Model
The Null Hypothesis
Aellips = 1.2(2)x10-4
Sept 15, 2011
Nick Cowan's Talk at ESS II
8
Interpreting Ellipsoidal Variations
Brightness Geometry
Phases
4.5 micron phase variations
most of cos(2) due
cos(2)
to geometry
all due to geometry
Spherical planet
Temperature profile is cos(- 0)
But applying Cowan & Agol (2008) deconvolution
All of cos(2) due to temperature
leads to unphysical longitudinal brightness map
some of cos(2) due to temperature
Sept 15, 2011
Nick Cowan's Talk at ESS II
9
Day-Side Emergent Spectrum
Null Hypothesis
(Campo et al. 2010)
This Study
(López- Morales
et al. 2010)
(Croll et al. 2011)
Day-Side 1D Model Spectra
(Burrows et al. 2007, 2008)
Sept 15, 2011
Nick Cowan's Talk at ESS II
10
Transmission Spectrum
(Maciejewski et al. 2011)
Transit Spectrum Assuming
Day-Like T-P Profile
(Burrows et al. 2007, 2008)
(Chan et al. 2011)
Sept 15, 2011
Nick Cowan's Talk at ESS II
11
Choose Your Own Adventure
1. Prediction-Buster
• Roche-Lobe Opaque at
4.5 m + Gravity
Brightened Terminator
• Weird Composition (not
just high C/O)
2. Null Hypothesis
• Ellipsoidal Variations
As Predicted
• Solar Composition?
QuickTime™ and a
decompressor
are needed to see this picture.
Sept 15, 2011
Nick Cowan's Talk at ESS II
12
WASP-12b Power Budget
Eclipse Observations
AB ≈ 0.25
 ≈ rad/(adv + rad) ≈ 0.1
Phase Observations
Hot Planets are Poor Recirculators (Cowan & Agol 2011b)
1. Magnetic Drag (Perna et al. 2010, Menou 2011)
2. Short Radiative Timescale (rad ≈ T-3)
Sept 15, 2011
Nick Cowan's Talk at ESS II
13
EXOCLIMES 2012
Aspen, CO
Jan 16-20, 2012
Registration Open
www.aspenphys.org
Sept 15, 2011
Nick Cowan's Talk at ESS II
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