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Title: The 4.5 μm full-orbit phase curve of the hot Jupiter HD 209458b

The hot Jupiter HD 209458b is particularly amenable to detailed study as it is among the brightest transiting exoplanet systems currently known (V-mag = 7.65; K-mag = 6.308) and has a large planet-to-star contrast ratio. HD 209458b is predicted to be in synchronous rotation about its host star with a hot spot that is shifted eastward of the substellar point by superrotating equatorial winds. Here we present the first full-orbit observations of HD 209458b, in which its 4.5 μm emission was recorded with Spitzer/IRAC. Our study revises the previous 4.5 μm measurement of HD 209458b's secondary eclipse emission downward by ∼35% to 0.1391%{sub −0.0069%}{sup +0.0072%}, changing our interpretation of the properties of its dayside atmosphere. We find that the hot spot on the planet's dayside is shifted eastward of the substellar point by 40.°9 ± 6.°0, in agreement with circulation models predicting equatorial superrotation. HD 209458b's dayside (T{sub bright} = 1499 ± 15 K) and nightside (T{sub bright} = 972 ± 44 K) emission indicate a day-to-night brightness temperature contrast smaller than that observed for more highly irradiated exoplanets, suggesting that the day-to-night temperature contrast may be partially a function of the incident stellar radiation. The observed phase curve shapemore » deviates modestly from global circulation model predictions potentially due to disequilibrium chemistry or deficiencies in the current hot CH{sub 4} line lists used in these models. Observations of the phase curve at additional wavelengths are needed in order to determine the possible presence and spatial extent of a dayside temperature inversion, as well as to improve our overall understanding of this planet's atmospheric circulation.« less
Authors:
; ;  [1] ;  [2] ;  [3] ; ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ;  [9] ;  [10]
  1. Lunar and Planetary Laboratory, University of Arizona, 1629 East University Boulevard, Tucson, AZ 85721 (United States)
  2. Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States)
  3. Division of Geological and Planetary Sciences, MC 170-25 1200 East California Boulevard, Pasadena, CA 91125 (United States)
  4. Department of Astronomy and Astrophysics, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States)
  5. Department of Earth and Planetary Sciences, Northwestern University, Technological Institute, 2145 Sheridan Road, Evanston, IL 60208 (United States)
  6. Astronomy Department, University of Washington, Physics-Astronomy Building, 3910 15th Avenue NE, Seattle, WA 98195 (United States)
  7. Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Peyton Hall, Princeton University, Princeton, NJ 08544 (United States)
  8. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street MS-16, Cambridge, MA 02138 (United States)
  9. Department of Astronomy, University of Maryland, College Park, MD 20742 (United States)
  10. Physics Department, Principia College, 1 Maybeck Place, Elsah, IL 62028 (United States)
Publication Date:
OSTI Identifier:
22365589
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 790; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ATMOSPHERIC CIRCULATION; BRIGHTNESS; ECLIPSE; EMISSION; HOT SPOTS; IRRADIATION; METHANE; ORBITS; ROTATION; SATELLITES; STARS; STELLAR RADIATION; TEMPERATURE INVERSIONS