SPITZER PHASE CURVE CONSTRAINTS for WASP-43b at 3.6 and 4.5 μm

Kevin B. Stevenson, Michael R. Line, Jacob L. Bean, Jean Michel Désert, Jonathan J. Fortney, Adam Showman, Tiffany Kataria, Laura Kreidberg, Y. Katherina Feng

Research output: Contribution to journalArticle

34 Citations (Scopus)

Abstract

Previous measurements of heat redistribution efficiency (the ability to transport energy from a planet's highly irradiated dayside to its eternally dark nightside) show considerable variation between exoplanets. Theoretical models predict a positive correlation between heat redistribution efficiency and temperature for tidally locked planets; however, recent Hubble Space Telescope (HST) WASP-43b spectroscopic phase curve results are inconsistent with current predictions. Using the Spitzer Space Telescope, we obtained a total of three phase curve observations of WASP-43b (P = 0.813 days) at 3.6 and 4.5 μm. The first 3.6 μm visit exhibits spurious nightside emission that requires invoking unphysical conditions in our cloud-free atmospheric retrievals. The two other visits exhibit strong day-night contrasts that are consistent with the HST data. To reconcile the departure from theoretical predictions, WASP-43b would need to have a high-altitude, nightside cloud/haze layer blocking its thermal emission. Clouds/hazes could be produced within the planet's cool, nearly retrograde mid-latitude flows before dispersing across its nightside at high altitudes. Since mid-latitude flows only materialize in fast-rotating ( day) planets, this may explain an observed trend connecting measured day-night contrast with planet rotation rate that matches all current Spitzer phase curve results. Combining independent planetary emission measurements from multiple phases, we obtain a precise dayside hemisphere H2O abundance ( at 1σ confidence) and, assuming chemical equilibrium and a scaled solar abundance pattern, we derive a corresponding metallicity estimate that is consistent with being solar (0.4-1.7). Using the retrieved global CO+CO2 abundance under the same assumptions, we estimate a comparable metallicity of 0.3-1.7 solar. This is the first time that precise abundance and metallicity constraints have been determined from multiple molecular tracers for a transiting exoplanet.

Original languageEnglish (US)
Article number68
JournalAstronomical Journal
Volume153
Issue number2
DOIs
StatePublished - Feb 1 2017

Fingerprint

planets
planet
metallicity
curves
haze
extrasolar planets
high altitude
Hubble Space Telescope
night
heat
Space Infrared Telescope Facility
dispersing
thermal emission
estimates
prediction
predictions
hemispheres
retrieval
tracers
chemical equilibrium

Keywords

  • planetary systems
  • stars: individual (WASP-43)
  • techniques: photometric

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Stevenson, K. B., Line, M. R., Bean, J. L., Désert, J. M., Fortney, J. J., Showman, A., ... Feng, Y. K. (2017). SPITZER PHASE CURVE CONSTRAINTS for WASP-43b at 3.6 and 4.5 μm. Astronomical Journal, 153(2), [68]. https://doi.org/10.3847/1538-3881/153/2/68

SPITZER PHASE CURVE CONSTRAINTS for WASP-43b at 3.6 and 4.5 μm. / Stevenson, Kevin B.; Line, Michael R.; Bean, Jacob L.; Désert, Jean Michel; Fortney, Jonathan J.; Showman, Adam; Kataria, Tiffany; Kreidberg, Laura; Feng, Y. Katherina.

In: Astronomical Journal, Vol. 153, No. 2, 68, 01.02.2017.

Research output: Contribution to journalArticle

Stevenson, KB, Line, MR, Bean, JL, Désert, JM, Fortney, JJ, Showman, A, Kataria, T, Kreidberg, L & Feng, YK 2017, 'SPITZER PHASE CURVE CONSTRAINTS for WASP-43b at 3.6 and 4.5 μm', Astronomical Journal, vol. 153, no. 2, 68. https://doi.org/10.3847/1538-3881/153/2/68
Stevenson, Kevin B. ; Line, Michael R. ; Bean, Jacob L. ; Désert, Jean Michel ; Fortney, Jonathan J. ; Showman, Adam ; Kataria, Tiffany ; Kreidberg, Laura ; Feng, Y. Katherina. / SPITZER PHASE CURVE CONSTRAINTS for WASP-43b at 3.6 and 4.5 μm. In: Astronomical Journal. 2017 ; Vol. 153, No. 2.
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