Thermal emission at 4.5 and 8μm of WASP-17b, an extremely large planet in a slightly eccentric orbit

D. R. Anderson, A. M S Smith, A. A. Lanotte, Travis S Barman, A. Collier Cameron, C. J. Campo, M. Gillon, J. Harrington, C. Hellier, P. F L Maxted, D. Queloz, A. H M J Triaud, P. J. Wheatley

Research output: Contribution to journalArticle

54 Citations (Scopus)

Abstract

We report the detection of thermal emission at 4.5 and 8μm from the planet WASP-17b. We used Spitzer to measure the system brightness at each wavelength during two occultations of the planet by its host star. By combining the resulting light curves with existing transit light curves and radial-velocity measurements in a simultaneous analysis, we find the radius of WASP-17b to be 2.0RJup, which is 0.2RJup larger than any other known planet and 0.7RJup larger than predicted by the standard cooling theory of irradiated gas giant planets. We find the retrograde orbit of WASP-17b to be slightly eccentric, with 0.0012 < e < 0.070 (3σ). Such a low eccentricity suggests that, under current models, tidal heating alone could not have bloated the planet to its current size, so the radius of WASP-17b is currently unexplained. From the measured planet-star flux-density ratios we infer 4.5 and 8μm brightness temperatures of 1881 ± 50 and 1580 ± 150K, respectively, consistent with a low-albedo planet that efficiently redistributes heat from its day side to its night side.

Original languageEnglish (US)
Pages (from-to)2108-2122
Number of pages15
JournalMonthly Notices of the Royal Astronomical Society
Volume416
Issue number3
DOIs
StatePublished - Sep 2011
Externally publishedYes

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eccentric orbits
thermal emission
planets
planet
light curve
retrograde orbits
gas giant planets
stars
radii
brightness temperature
occultation
eccentrics
transit
albedo
eccentricity
velocity measurement
night
radial velocity
brightness
flux density

Keywords

  • Methods: data analysis
  • Occultations
  • Planets and satellites: atmospheres
  • Planets and satellites: individual: WASP-17b
  • Stars: individual: WASP-17
  • Techniques: photometric

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Thermal emission at 4.5 and 8μm of WASP-17b, an extremely large planet in a slightly eccentric orbit. / Anderson, D. R.; Smith, A. M S; Lanotte, A. A.; Barman, Travis S; Cameron, A. Collier; Campo, C. J.; Gillon, M.; Harrington, J.; Hellier, C.; Maxted, P. F L; Queloz, D.; Triaud, A. H M J; Wheatley, P. J.

In: Monthly Notices of the Royal Astronomical Society, Vol. 416, No. 3, 09.2011, p. 2108-2122.

Research output: Contribution to journalArticle

Anderson, DR, Smith, AMS, Lanotte, AA, Barman, TS, Cameron, AC, Campo, CJ, Gillon, M, Harrington, J, Hellier, C, Maxted, PFL, Queloz, D, Triaud, AHMJ & Wheatley, PJ 2011, 'Thermal emission at 4.5 and 8μm of WASP-17b, an extremely large planet in a slightly eccentric orbit', Monthly Notices of the Royal Astronomical Society, vol. 416, no. 3, pp. 2108-2122. https://doi.org/10.1111/j.1365-2966.2011.19182.x
Anderson, D. R. ; Smith, A. M S ; Lanotte, A. A. ; Barman, Travis S ; Cameron, A. Collier ; Campo, C. J. ; Gillon, M. ; Harrington, J. ; Hellier, C. ; Maxted, P. F L ; Queloz, D. ; Triaud, A. H M J ; Wheatley, P. J. / Thermal emission at 4.5 and 8μm of WASP-17b, an extremely large planet in a slightly eccentric orbit. In: Monthly Notices of the Royal Astronomical Society. 2011 ; Vol. 416, No. 3. pp. 2108-2122.
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abstract = "We report the detection of thermal emission at 4.5 and 8μm from the planet WASP-17b. We used Spitzer to measure the system brightness at each wavelength during two occultations of the planet by its host star. By combining the resulting light curves with existing transit light curves and radial-velocity measurements in a simultaneous analysis, we find the radius of WASP-17b to be 2.0RJup, which is 0.2RJup larger than any other known planet and 0.7RJup larger than predicted by the standard cooling theory of irradiated gas giant planets. We find the retrograde orbit of WASP-17b to be slightly eccentric, with 0.0012 < e < 0.070 (3σ). Such a low eccentricity suggests that, under current models, tidal heating alone could not have bloated the planet to its current size, so the radius of WASP-17b is currently unexplained. From the measured planet-star flux-density ratios we infer 4.5 and 8μm brightness temperatures of 1881 ± 50 and 1580 ± 150K, respectively, consistent with a low-albedo planet that efficiently redistributes heat from its day side to its night side.",
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T1 - Thermal emission at 4.5 and 8μm of WASP-17b, an extremely large planet in a slightly eccentric orbit

AU - Anderson, D. R.

AU - Smith, A. M S

AU - Lanotte, A. A.

AU - Barman, Travis S

AU - Cameron, A. Collier

AU - Campo, C. J.

AU - Gillon, M.

AU - Harrington, J.

AU - Hellier, C.

AU - Maxted, P. F L

AU - Queloz, D.

AU - Triaud, A. H M J

AU - Wheatley, P. J.

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AB - We report the detection of thermal emission at 4.5 and 8μm from the planet WASP-17b. We used Spitzer to measure the system brightness at each wavelength during two occultations of the planet by its host star. By combining the resulting light curves with existing transit light curves and radial-velocity measurements in a simultaneous analysis, we find the radius of WASP-17b to be 2.0RJup, which is 0.2RJup larger than any other known planet and 0.7RJup larger than predicted by the standard cooling theory of irradiated gas giant planets. We find the retrograde orbit of WASP-17b to be slightly eccentric, with 0.0012 < e < 0.070 (3σ). Such a low eccentricity suggests that, under current models, tidal heating alone could not have bloated the planet to its current size, so the radius of WASP-17b is currently unexplained. From the measured planet-star flux-density ratios we infer 4.5 and 8μm brightness temperatures of 1881 ± 50 and 1580 ± 150K, respectively, consistent with a low-albedo planet that efficiently redistributes heat from its day side to its night side.

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KW - Techniques: photometric

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