The Complete Transmission Spectrum of WASP-39b with a Precise Water Constraint

H. R. Wakeford, D. K. Sing, D. Deming, N. K. Lewis, J. Goyal, T. J. Wilson, J. Barstow, T. Kataria, B. Drummond, T. M. Evans, A. L. Carter, N. Nikolov, H. A. Knutson, G. E. Ballester, A. M. Mandell

Research output: Contribution to journalArticlepeer-review

108 Scopus citations


WASP-39b is a hot Saturn-mass exoplanet with a predicted clear atmosphere based on observations in the optical and infrared. Here, we complete the transmission spectrum of the atmosphere with observations in the near-infrared (NIR) over three water absorption features with the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) G102 (0.8-1.1 μm) and G141 (1.1-1.7 μm) spectroscopic grisms. We measure the predicted high-amplitude H2O feature centered at 1.4 μm and the smaller amplitude features at 0.95 and 1.2 μm, with a maximum water absorption amplitude of 2.4 planetary scale heights. We incorporate these new NIR measurements into previously published observational measurements to complete the transmission spectrum from 0.3 to 5 μm. From these observed water features, combined with features in the optical and IR, we retrieve a well constrained temperature T eq =1030+30-20 K, and atmospheric metallicity 151+48-46solar, which is relatively high with respect to the currently established mass-metallicity trends. This new measurement in the Saturn-mass range hints at further diversity in the planet formation process relative to our solar system giants.

Original languageEnglish (US)
Article number29
JournalAstronomical Journal
Issue number1
StatePublished - Jan 2018


  • Planets and satellites: atmospheres
  • planets and satellites: individual (WASP-39b)
  • techniques: spectroscopic

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


Dive into the research topics of 'The Complete Transmission Spectrum of WASP-39b with a Precise Water Constraint'. Together they form a unique fingerprint.

Cite this