WARM SPITZER PHASE VARIATIONS OF WASP-12B:

DEFYING PREDICTIONS

Nick CowanCIERA Postdoctoral Fellow

Northwestern University

September 15th 2011with Louis Shekhtman (NU undergrad)Machalek, Croll, Burrows, Deming

Sept 15, 2011 Nick Cowan's Talk at ESS II 2

WASP-12b: a Tortured World• ~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(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:Crossfield 40.08

Petigura 33.03

Moses 40.04

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Li et al. (2010)

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Thermal + Ellipsoidal Variations

HAT-P-7b as seen by Kepler(Welsh et al. 2010)

Brightness Phases: Planet Light

Geometrical Phases:Projected Area

Optical Light Observations• Reflected Light Dominates Phases • Star’s Shape Dominates Geometry

Infrared Observations• Thermal Emission Dominates Phases• Planet’s Shape Dominates Geometry

Sept 15, 2011 Nick Cowan's Talk at ESS II 4

Raw WASP-12b Photometry

3.6 micron 4.5 micron Transit

EclipseEclipse

Phase Function

Intra-pixel sensitivity variations are the dominant systematic1. Gaussian Decorrelation (Ballard et al. 2010)

2. Polynomial in Centroid x and y

Sept 15, 2011 Nick Cowan's Talk at ESS II 5

WASP-12b at 3.6 micron

max = -53(7)°Atherm/<Fp> = 0.9(3)

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What Planets Are Supposed To Do

NoonSOP

DawnSOP

MidnightSOP

Dusk SOP

Increasing Heat Capacity1) Decreases Thermal Phase Amplitude2) Increases Hot Spot Offset

Co

wa

n &

Ag

ol (

201

1a)

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WASP-12b at 3.6 micron

max = -53(7)°

Aellips = 2(2)x10-4

Atherm/<Fp> = 0.9(3)

Sept 15, 2011 Nick Cowan's Talk at ESS II 8

WASP-12b at 4.5 micron

max = -16(4)°

Aellips = 1.2(2)x10-4

Atherm/<Fp> = 0.7(1)

The Null Hypothesis

Consistent with Cowan & Agol (2011a) Toy Model

Sept 15, 2011 Nick Cowan's Talk at ESS II 9

Interpreting Ellipsoidal Variations4.5 micron phase variations

Temperature profile is cos(- 0)

some of cos(2) due to temperature

All of cos(2) due to temperature

cos(2) all due to geometry

Spherical planet

most of cos(2) due to geometry

But applying Cowan & Agol (2008) deconvolutionleads to unphysical longitudinal brightness map

Geo

met

ryP

hase

sB

right

ness

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Day-Side Emergent Spectrum

Day-Side 1D Model Spectra(Burrows et al. 2007, 2008)

(Croll et al. 2011)

(López- Morales et al. 2010)

(Campo et al. 2010)

This Study

Null Hypothesis

Sept 15, 2011 Nick Cowan's Talk at ESS II 11

Transmission Spectrum

(Chan et al. 2011)

(Maciejewski et al. 2011)

Transit Spectrum Assuming Day-Like T-P Profile(Burrows et al. 2007, 2008)

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Choose Your Own Adventure1. 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?

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WASP-12b Power Budget

Eclipse Observations

Phase Observations

AB ≈ 0.25 ≈ rad/(adv + rad) ≈ 0.1

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 14

EXOCLIMES 2012Aspen, CO

Jan 16-20, 2012

Registration Openwww.aspenphys.org