Wakeford, HR; Sing, DK; Deming, D; Lewis, NK; Goyal, J; Wilson, TJ; Barstow, J; ... Mandell, AM; + view all Wakeford, HR; Sing, DK; Deming, D; Lewis, NK; Goyal, J; Wilson, TJ; Barstow, J; Kataria, T; Drummond, B; Evans, TM; Carter, AL; Nikolov, N; Knutson, HA; Ballester, GE; Mandell, AM; - view fewer (2018) The Complete Transmission Spectrum of WASP-39b with a Precise Water Constraint. Astronomical Journal , 155 (1) 10.3847/1538-3881/aa9e4e.

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Abstract

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${}_{-20}^{+30}$ K, and atmospheric metallicity ${151}_{-46}^{+48}\times $ solar, 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.

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