Theoretical Spectra and Light Curves of Close-in Extrasolar Giant Planets and Comparison with Data

By Adam Burrows, J. Budaj, I. Hubeny. 2007

238 citations recorded by the source corpus.

We present theoretical atmosphere, spectral, and light-curve models for extrasolar giant planets (EGPs) undergoing strong irradiation for which Spitzer planet/star contrast ratios or light curves have been published (circa 2007 June). These include HD 209458b, HD 189733b, TrES-1, HD 149026b, HD 179949b, and υ And b. By comparing models with data, we find that a number of EGP atmospheres experience thermal inversions and have stratospheres. This is particularly true for HD 209458b, HD 149026b, and υ And b. This finding translates into qualitative changes in the planet/star contrast ratios at secondary eclipse and in close-in EGP orbital light curves. Moreover, the presence of atmospheric water in abundance is fully consistent with all the Spitzer data for the measured planets. For planets with stratospheres, water absorption features invert into emission features and mid-infrared fluxes can be enhanced by a factor of 2. In addition, the character of near-infrared planetary spectra can be radically altered. We derive a correlation between the importance of such stratospheres and the stellar flux on the planet, suggesting that close-in EGPs bifurcate into two groups: those with and without stratospheres. From the finding that TrES-1 shows no signs of a stratosphere, while HD 209458b does, we estimate the magnitude of this stellar flux breakpoint. We find that the heat redistribution parameter, Pn, for the family of close-in EGPs assumes values from ~0.1 to ~0.4. This paper provides a broad theoretical context for the future direct characterization of EGPs in tight orbits around their illuminating stars.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/3f43914f5b4b7a673521301df2f472b0228834f6

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In Astronomy and Astrophysics

1. N. Madhusudhan
2. Jon Fortney
3. A. Showman
4. M. Marley
5. H. Knutson
6. M. Line
7. D. Deming
8. D. Charbonneau

Citations in the corpus

• Optimal estimation retrievals of the atmospheric structure and composition of HD 189733b from secondary eclipse spectroscopy (2011, background): “…aecreasing temperature layer between 0.01 and 1 bar to model the HST /NICMOS measurements, making an adiabatic layer∼10 times thicker than our estimation, and theoretical models also considered adiabatic layers in the troposphere (Fortney et al.2006; Burrows et al. 2008; Showman et al. 2008).”
• MULTIWAVELENGTH CONSTRAINTS ON THE DAY–NIGHT CIRCULATION PATTERNS OF HD 189733b (2008, methodology): “In this picture, temperature inversions would be correlated with the degree of irradiation, with a distinct division between the two classes of planets set by the condensation temperature of TiO/VO (Fortney et al. 2008; Burrows et al. 2008).”
• H− Opacity and Water Dissociation in the Dayside Atmosphere of the Very Hot Gas Giant WASP-18b (2018, background): “Strong irradiation combined with efficient optical absorbers in the atmosphere (such as TiO and VO in gas-phase) could cause an inversion layer in the temperature-pressure profile (Fortney et al. 2006, 2008; Burrows et al. 2008; Parmentier et al. 2015).”
• A chemical model for the atmosphere of hot Jupiters (2012, background): “The first models of hot Jupiter atmospheres assumed chemical equilibrium (e.g. Burrows & Sharp 1999; Seager & Sasselov 2000; Sharp & Burrows 2007; Barman 2007; Burrows et al. 2007, 2008; Fortney et al. 2008a).”
•  ?> -REx. II. RETRIEVAL OF EMISSION SPECTRA (2015, background): “…to the relevant literature for a more in-depth discussion on the various analytic approaches (e.g. Liou 2002; Hubeny et al. 2003; Hansen 2008; Burrows et al. 2008; Showman et al. 2009; Madhusudhan & Seager 2009; Pierrehumbert 2010; Guillot 2010; Heng et al. 2012, 2014; Robinson & Catling…”
• A TEMPERATURE AND ABUNDANCE RETRIEVAL METHOD FOR EXOPLANET ATMOSPHERES (2009, methodology): “Temperature Structure The most interesting aspect about the atmosphere of HD 209458b is the presence of a thermal inversion on the planet dayside, as previous studies have pointed out (e.g., Burrows et al. 2008).”
• ATMOSPHERIC RETRIEVAL FOR SUPER-EARTHS: UNIQUELY CONSTRAINING THE ATMOSPHERIC COMPOSITION WITH TRANSMISSION SPECTROSCOPY (2012, methodology): “…Retrieval versus Detailed Atmospheric Modeling The atmospheric retrieval method and detailed, self-consistent modeling of a planetary atmosphere (Burrows et al. 1997; Seager et al. 2005; Burrows et al. 2008) present two completely complementary approaches to the study of planetary atmospheres.”
• ORBITAL PHASE VARIATIONS OF THE ECCENTRIC GIANT PLANET HAT-P-2b (2013, methodology): “Figure 14 presents predicted day side emission as a function of wavelength from a onedimensional radiative transfer model similar to those described in Burrows et al. (2008).”
• Magnetic activity in the photosphere of CoRoT-Exo-2a. Active longitudes and short-term spot cycle in (2008, methodology): “The light reflected by the planet reaches 1.0 × 10−4 in relative flux units if we adopt a geometric albedo of 13 percent, that is quite high in view of the hot Jupiter atmospheric models computed by, e.g., Sudarsky et al. (2000), Seager et al. (2000), Burrows et al. (2008).”
• ATMOSPHERIC CIRCULATION OF HOT JUPITERS: COUPLED RADIATIVE-DYNAMICAL GENERAL CIRCULATION MODEL SIMULATIONS OF HD 189733b and HD 209458b (2008, unknown): “Following pioneering work by Hubeny et al. (2003), Fortney et al. (2008) and Burrows et al. (2008) suggested that 6 At 8µm, the dayside and nightside brightness temperatures are 1258± 11K and 1011± 51K.”
• 3.6 AND 4.5 μm PHASE CURVES AND EVIDENCE FOR NON-EQUILIBRIUM CHEMISTRY IN THE ATMOSPHERE OF EXTRASOLAR PLANET HD 189733b (2012, background): “We fit the planet’s dayside spectrum with a 1D radiative transfer model from Burrows et al. (2008) where the amount of energy transported to the night side is left as a free parameter and find that the corresponding nightside spectrum is in good agreement with our measured values.”
• THE STATISTICS OF ALBEDO AND HEAT RECIRCULATION ON HOT EXOPLANETS (2009, background): “By integrating Equation 3 over λ, one obtains the effective temperature of the day-side in the no-albedo, no-circulation limit: Tε=0 = (2/3) 1/4T0 (see also Burrows et al. 2008; Hansen 2008).”
• Exoplanet Atmospheres: Physical Processes (2010, background): “Spitzer data show that the upper atmospheres of several planets have thermal inversions, if water vapor is present and if abundances are close to solar (e.g., Burrows et al. 2008; see Figure 10).”
• ATMOSPHERIC SULFUR PHOTOCHEMISTRY ON HOT JUPITERS (2009, background): “One suggestion is that temperature inversions are triggered by irradiation reaching a critical level that is hot enough to evaporate TiO and VO from grains, as discussed by Burrows et al. (2007), Fortney et al. (2008), and Burrows et al. (2008).”
• THERMAL PHASE VARIATIONS OF WASP-12b: DEFYING PREDICTIONS (2011, unknown): “The best-fit ellipsoidal variations at 3.6 μ m are consistent with the predicted amplitude of 2 × 10 − 4 , but as one can see (Burrows et al. 2007, 2008), while the red points show the measured secondary eclipse depths.”
• CAN TiO EXPLAIN THERMAL INVERSIONS IN THE UPPER ATMOSPHERES OF IRRADIATED GIANT PLANETS? (2009, methodology): “To generate temperature-pressure profiles and spectra for the day and night sides of several EGPs, we compute model atmospheres with the code COOLTLUSTY, described in Hubeny et al. (2003), Sudarsky et al. (2003), Burrows et al. (2006), and Burrows et al. (2008).”
• C/O RATIO AS A DIMENSION FOR CHARACTERIZING EXOPLANETARY ATMOSPHERES (2012, methodology): “…compositions of six hot Jupiters with different levels of incident irradiation: XO-1b, CoRoT-2b, WASP- 4 This approach is different from other forward models which typically assume solar abundances for exoplanetary atmospheres (e.g. Seager et al. 2005; Burrows et al. 2008; Fortney et al. 2008).”
• THE CLIMATE OF HD 189733b FROM FOURTEEN TRANSITS AND ECLIPSES MEASURED BY SPITZER (2010, background): “…models, such as Showman et al. (2009a) and Rauscher and Menou (2010), while two-hemisphere models have more difficulty explaining the shape and variation of the phase function (Burrows et al. 2008); see the recent review by Showman et al. (2009b) for a detailed discussion of these models.”