Theory for Giant Exoplanets A Potpourri A Burrows
“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 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 Tr. ES-4 HD 149. . GJ 436 b WASP-12 b Spread in Rp (in Optical and IR): 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-14 b HAT-P-3 b Burrows et al. 2007 Note measurement of HAT-P-1 b 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 HD 209458 b 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?
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, …: 530% 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 HD 209458 b: 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 209458 b: Transit Radius vs. Wavelength Burrows, Rauscher, Spiegel, & Menou 2010 see also Fortney et al. 2010
HD 209458 b: 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 H 2 O
? Water CH 4 ? 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 Ti. O OGLE-Tr-56 b
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! ! H 2 O IRAC 1 < IRAC 2 ! Burrows et al. 2007
Indices of Upper-Atmosphere Heating and Inversion: F Inversion: IRAC 2/IRAC 1 - High “Bump” at IRAC 3 (water in emission? ) - “other” emission features F Hot Upper Atmosphere: “High” planet-star flux ratios in IRAC 2, IRAC 3, and IRAC 4 bands (and at 24 microns? ) F Hot Spot advection? ? F What is absorbing in the optical at altitude?
Spiegel, Silverio, & Burrows 2009
Solar abundance Ti. O (at limb) inconsistent with transit observations! Ti. O/VO cross sections Désert et al. 2008
Can gas-phase Ti. O 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? F Extra absorber in the Optical at Altitude (low pressures)? F Can it be Ti. O/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 209458 b) F Sulfur chemistry and photolysis: Thiozone (S 3), allotropes of S, HS (Zahnle et al. 2009) - metallicity dependence (XO-2 b)? F Only weakly correlated with stellar insolation (e. g. , XO 1 b and HD 189733 b!) - no simple parametrization! F Wave heating? ? F C/O > 1 (? ) (Madhusudhan et al. ); but need hot upper atmospheres F Theory: Need non-equilibrium chemistry & 3 D GCM to resolve? F Observation: Need better and more definitive optical spectra
Secondary Eclipses in the Optical: MOST, Kepler, and Co. Ro. T “Albedos”
Close-in EGPs
MOST HD 209458 b Albedo: Burrows, Ibgui, & Hubeny 2008 Rowe et al. 2007 !!
Co. Ro. T-1 b(Optical and K band): Rogers et al. 2009
Co. Ro. T-2 b(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 209458 b Map (model a 03) Burrows et al. 2010
IRAC 3 band HD 209458 b Map (model a 03)
I band HD 209458 b Map (model a 03)
HD 209458 b: Integrated Phase Light Curves: With inversion/hot upper atmosphere -dependent Trough/peak shifts Burrows, Rauscher, Spiegel, & Menou 2010
HD 209458 b: 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 8799 bcd(e) Mb ~ 7 M J 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 8799 b 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 § § § § § 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!)?
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