STUDYING THE ATMOSPHERE OF THE EXOPLANET HAT-P-7b VIA SECONDARY ECLIPSE MEASUREMENTS WITH EPOXI, SPITZER, AND KEPLER

Journal Article · Wed Feb 10 00:00:00 EST 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/710/1/97· OSTI ID:21394531

Christiansen, Jessie L; Ballard, Sarah; Charbonneau, David; Holman, Matthew J ^[1]; Madhusudhan, Nikku; Seager, Sara ^[2]; Wellnitz, Dennis D; Deming, Drake

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1. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
2. Massachusetts Institute of Technology, Cambridge, MA 02159 (United States)

The highly irradiated transiting exoplanet, HAT-P-7b, currently provides one of the best opportunities for studying planetary emission in the optical and infrared wavelengths. We observe six near-consecutive secondary eclipses of HAT-P-7b at optical wavelengths with the EPOXI spacecraft. We place an upper limit on the relative eclipse depth of 0.055% (95% confidence). We also analyze Spitzer observations of the same target in the infrared, obtaining secondary eclipse depths of 0.098% +- 0.017%, 0.159% +- 0.022%, 0.245% +- 0.031%, and 0.225% +- 0.052% in the 3.6, 4.5, 5.8, and 8.0 {mu}m IRAC bands, respectively. We combine these measurements with the recently published Kepler secondary eclipse measurement and generate atmospheric models for the dayside of the planet that are consistent with both the optical and infrared measurements. The data are best fit by models with a temperature inversion, as expected from the high incident flux. The models predict a low optical albedo of {approx}<0.13, with subsolar abundances of Na, K, TiO, and VO. We also find that the best-fitting models predict that 10% of the absorbed stellar flux is redistributed to the nightside of the planet, which is qualitatively consistent with the inefficient day-night redistribution apparent in the Kepler phase curve. Models without thermal inversions fit the data only at the 1.25sigma level, and also require an overabundance of methane, which is not expected in the very hot atmosphere of HAT-P-7b. We also analyze the eight transits of HAT-P-7b present in the EPOXI data set and improve the constraints on the system parameters, finding a period of P = 2.2047308 +- 0.0000025 days, a stellar radius of R{sub *} = 1.824 +- 0.089 R{sub sun}, a planetary radius of R{sub p} = 1.342 +- 0.068 R{sub Jup}, and an inclination of i = 85.7{sup +3.5}{sub -2.2} deg.

• OSTI ID: 21394531
• Journal Information: Astrophysical Journal, Vol. 710, Issue 1; Other Information: DOI: 10.1088/0004-637X/710/1/97; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABUNDANCE
ALBEDO
ECLIPSE
INCLINATION
METHANE
PLANETS
POTASSIUM
SODIUM
STARS
TEMPERATURE INVERSIONS
TITANIUM OXIDES
VANADIUM OXIDES
WAVELENGTHS
ALKALI METALS
ALKANES
CHALCOGENIDES
ELEMENTS
HYDROCARBONS
METALS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
VANADIUM COMPOUNDS