Transcript Theory for Giant Exoplanets: A Potpourri”

“Theory for Giant Exoplanets:
A Potpourri”
A. Burrows
Dept. of Astrophysical Sciences
Princeton University
With collaborators D. Spiegel, I. Hubeny, N. Madhusudhan,
K. Heng, J. Budaj, …
Outline
 Transits of Giant planets (EGPs): Rp vs. M
(and Brown Dwarf Rp vs. M)
 The “Deuterium Burning” Limit
 Wavelength-Dependence of Transit Radius
 “Hot Jupiter” Secondary Eclipse Spectra
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Temperature-Pressure Profiles
Optical Albedos
Photometric Light Curves
Variation of Spectra with Planetary Phase
Planet thermal, composition, brightness Maps
High-Contrast Imaging (wide-separation)
Distinguishing the Modes of Giant Planet Formation
Radius-Mass Relationship for
Irradiated EGPs (“Hot Jupiters”)
(dependence on age, star,
semi-major axis distance,
planet mass, “core mass,”
atmospheric opacities)
Transit Radius vs. Planet Mass
TrES-4
WASP-12b
Spread in Rp (in Optical and IR):
HD 149 ..
GJ 436b
Radius “anomalies”: Some are
“small” and some are “large”
Larger EGPs: Models vs. Data
Higher Opacity/Metallicity Atmospheres increase radii
Smaller EGPs: Models vs. Data
Radius Deficits: Need “ice/rock” cores?
Approximate “Core” Mass vs. Stellar Metallicity
HAT-P-14b
HAT-P-3b
Burrows
et al.
2007
Note measurement of HAT-P-1b
See also Guillot et al.
2006
Core Entropy vs. Radius for Transiting Planets
Spiegel & Burrows 2011
Effects of Extra Core Heating on EGP Radii
Large
Radiative
Zone, slowly
moving
inward
Irradiated
Atmosphere
of
HD209458b
Irradiation inhibits flow
of Heat from the Core
Outside
Unchanged
t ~ 106
Day- and night-side cooling done consistently
Spiegel & Burrows 2011
T/P Profiles as a Function of Joule Heating
Spiegel & Burrows 2011 Guillot & Showman 2002 hypothesis? Yes
Radius Evolution with Heating in the Radiative
Zone
Spiegel & Burrows 2011
Core Cooling versus Core Heating: No Instability
No radius instability
due to B-fields
Spiegel & Burrows 2011
Brown dwarf
Radii (when we
know the Mass
and have an
estimate of the
age (?)ambiguous
interpretations
Burrows et al.
2011
Brown dwarf
Radii - functions
of metallicity,
clouds, …: 5-30%
Brown dwarf
Radii - Not just a
test of the EOS!
Burrows et al.
2011
Deuterium-Burning Mass
Spiegel, Burrows, and Milsom
2011
Evolution
Stars
Brown Dwarfs?
Planets
Burrows et al.
2001
Roughly 13 MJ, but
model-dependent.
More helium, more
deuterium, and higher
opacity result in lower Dburning mass.
What is meant by “deuterium
burning”?
Changing the “deuteriumburning criterion” from 10% to
50%, and also from 50% to 90%
changes the required mass by
nearly 1 MJ!
Spiegel, Burrows, Milsom 2011
Wavelength-Dependence of the
Transit Radius
“Transmission Spectroscopy”
With upperatmosphere
optical
absorber
Transit chord
Graphics by
D. Spiegel
Na-D
HD209458b:
Radius is Larger in Na-D!
Na detection: Charbonneau et al. 2003
Transit Radius vs. Wavelength
aka. “transmission spectroscopy”?
Fortney et al. 2003
Fractional Atmosphere vs. Wavelength
Burrows, Rauscher, Spiegel, & Menou 2010
HD 209458b: Transit Radius vs. Wavelength
Burrows, Rauscher, Spiegel, & Menou 2010
see also Fortney et al. 2010
HD 209458b: Transit Radius vs. Wavelength Measuring Orbit and Wind Speeds?
Ingress vs. Egress
Using Burrows, Rauscher, Spiegel, & Menou 2010
“Hot Jupiter” Spectra and
Temperature-Pressure Profiles
Secondary Eclipses
Thermal Inversions?
IRAC 1 > IRAC 2 !
Burrows, Budaj, & Hubeny 2008
Mostly H2 O
?
Water
CH4 ?
CO
JWST!!
Hot Upper Atmospheres and
Inversions
Heated upper atmosphere!
IRAC 1 < IRAC 2 !
Thermal Inversions: Water (etc.) in Emission (!)
Strong Absorber at Altitude (in the Optical)
Hubeny, Burrows, &
Sudarsky 2003
Burrows et al. 2007
w. Inversion
w/o Inversion
Toy Model
assumed TiO
OGLE-Tr-56b
Probing Structure During Secondary Eclipse
Comparing theoretical models with data (particularly Spitzer, but
increasingly ground-based too) allows us to place constraints on
composition and atmospheric structure and dynamics.
Observed
(low-res) spectrum!
Spiegel, Silverio, & Burrows
2009
1-D Approaches: Thermochemical equilibrium (Burrows, Fortney, Barman)
Water in
Emission!
!
H2 O
IRAC 1 < IRAC 2 !
Burrows et al. 2007
Indices of Upper-Atmosphere
Heating and Inversion:
 Inversion: IRAC 2/IRAC1 - High “Bump” at IRAC3
(water in emission?) - “other” emission features
 Hot Upper Atmosphere: “High” planet-star flux
ratios in IRAC 2, IRAC 3, and IRAC 4 bands (and at
24 microns?)
 Hot Spot advection??
 What is absorbing in the optical at altitude?
Spiegel, Silverio, & Burrows
Solar abundance TiO (at limb)
inconsistent with
transit observations!
TiO/VO cross sections
Désert et al. 2008
Can gas-phase
TiO explain
temperature
inversions?
Problem: inversions do not appear
to correlate with temperature
One alternative:
sulfur photochemistry
(Zahnle et al. 2009)
Inversion
No Inversion
As described in Hubeny et al. (2003),
Burrows et al. (2007, 2008), and Fortney
et al. (2008)
Figure from Fortney et al. (2008)
Cause of Heating in Upper Atmosphere?
 Extra absorber in the Optical at Altitude (low pressures)?
 Can it be TiO/VO (Hubeny et al. 2003; Burrows et al.
2008; Fortney et al. 2008)?
-“Can’t” be at equilibrium abundances (Fortney et al.): cold trap
(condenses out), day-night circulation sink; Heavies settle; Needs
vigorous vertical mixing to work (Spiegel et al. 2009!) - problematic? Desart et al. (?): < ~10-2 - 10-3 solar (HD 209458b)
 Sulfur chemistry and photolysis: Thiozone (S3),
allotropes of S, HS (Zahnle et al. 2009) - metallicity
dependence (XO-2b)?
 Only weakly correlated with stellar insolation (e.g., XO1b and HD 189733b!) - no simple parametrization!
 Wave heating??
 C/O > 1 (?) (Madhusudhan et al.); but need hot upper
atmospheres
 Theory: Need non-equilibrium chemistry & 3D GCM to
resolve?
 Observation: Need better and more definitive optical
spectra
Secondary Eclipses in the
Optical: MOST, Kepler, and
CoRoT
“Albedos”
Close-in EGPs
MOST HD 209458b Albedo: Burrows, Ibgui, & Hubeny 2008
Rowe et al. 2007
!!
CoRoT-1b(Optical and K band): Rogers et al. 2009
CoRoT-2b(Optical and IRAC): Snellen et al.
2009
Spiegel & Burrows 2010
Planetary Light Curves and
Spectral Variation with Phase
(Close-in)
(Photometric Variations)
Planet/Star Flux Ratio vs. Wavelength and Phase
Burrows, Rauscher, Spiegel, & Menou 2010
J-band HD
209458b Map
(model a03)
Burrows
et al. 2010
IRAC3 band
HD 209458b
Map (model
a03)
I band HD
209458b Map
(model a03)
HD 209458b: Integrated Phase Light Curves:
With inversion/hot upper atmosphere
-dependent
Trough/peak shifts
Burrows, Rauscher, Spiegel, & Menou 2010
HD 209458b: Integrated Phase Light Curves:
No upper atmosphere absorber
-dependent
Trough/peak shifts
Burrows, Rauscher, Spiegel, & Menou 2010
Remote Sensing of Exoplanets
(Direct Detection and Imaging
of planetary systems)
Fomalhaut b
a ~ 115 AU !!
Kalas et al. 2008;
< 3 MJ
HR
8799bcd(e)
Mb ~ 7 MJ
Mc ~10 MJ
Md~10 MJ
D = 24, 38, 68 AU
Marois et al. 2008
Very Dusty Atmospheres - low gravity?
Madhusudhan, Burrows, & Currie 2011
HR 8799b
See also Barman et al.; nonequilibrium chemistry?
Spectroscopic and Photometric
Discriminants of Giant Planet Formation
Scenaros
D. Spiegel and A. Burrows
2011
JWST?
Theoretical Questions
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What limits super-rotational
atmospheric flows?
Day/Night Contrasts?
What is the “extra absorber” in many
hot-EGP atmospheres?
Why are some “Hot Jupiters” so large
(Rp vs. Mp)?
Is there a dynamical, structural, and/or
thermal role for B-fields?
What condensates reside in planetary
atmospheres?
Winds and Evaporation?
Tidal Effects?
Atmospheric, Envelope, and Core
compositions?
Mode(s) of Formation (and
Signatures!)?