TY - JOUR
T1 - HST HOT-JUPITER TRANSMISSION SPECTRAL SURVEY
T2 - CLEAR SKIES for COOL SATURN WASP-39b
AU - Fischer, Patrick D.
AU - Knutson, Heather A.
AU - Sing, David K.
AU - Henry, Gregory W.
AU - Williamson, Michael W.
AU - Fortney, Jonathan J.
AU - Burrows, Adam S.
AU - Kataria, Tiffany
AU - Nikolov, Nikolay
AU - Showman, Adam P.
AU - Ballester, Gilda E.
AU - Désert, Jean Michel
AU - Aigrain, Suzanne
AU - Deming, Drake
AU - Etangs, Alain Lecavelier Des
AU - Vidal-Madjar, Alfred
N1 - Publisher Copyright:
© 2016. The American Astronomical Society. All rights reserved.
PY - 2016/8/10
Y1 - 2016/8/10
N2 - We present the Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) optical transmission spectroscopy of the cool Saturn-mass exoplanet WASP-39b from 0.29-1.025 μm, along with complementary transit observations from Spitzer IRAC at 3.6 and 4.5 μm. The low density and large atmospheric pressure scale height of WASP-39b make it particularly amenable to atmospheric characterization using this technique. We detect a Rayleigh scattering slope as well as sodium and potassium absorption features; this is the first exoplanet in which both alkali features are clearly detected with the extended wings predicted by cloud-free atmosphere models. The full transmission spectrum is well matched by a clear H2-dominated atmosphere, or one containing a weak contribution from haze, in good agreement with the preliminary reduction of these data presented in Sing et al. WASP-39b is predicted to have a pressure-temperature profile comparable to that of HD 189733b and WASP-6b, making it one of the coolest transiting gas giants observed in our HST STIS survey. Despite this similarity, WASP-39b appears to be largely cloud-free, while the transmission spectra of HD 189733b and WASP-6b both indicate the presence of high altitude clouds or hazes. These observations further emphasize the surprising diversity of cloudy and cloud-free gas giant planets in short-period orbits and the corresponding challenges associated with developing predictive cloud models for these atmospheres.
AB - We present the Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) optical transmission spectroscopy of the cool Saturn-mass exoplanet WASP-39b from 0.29-1.025 μm, along with complementary transit observations from Spitzer IRAC at 3.6 and 4.5 μm. The low density and large atmospheric pressure scale height of WASP-39b make it particularly amenable to atmospheric characterization using this technique. We detect a Rayleigh scattering slope as well as sodium and potassium absorption features; this is the first exoplanet in which both alkali features are clearly detected with the extended wings predicted by cloud-free atmosphere models. The full transmission spectrum is well matched by a clear H2-dominated atmosphere, or one containing a weak contribution from haze, in good agreement with the preliminary reduction of these data presented in Sing et al. WASP-39b is predicted to have a pressure-temperature profile comparable to that of HD 189733b and WASP-6b, making it one of the coolest transiting gas giants observed in our HST STIS survey. Despite this similarity, WASP-39b appears to be largely cloud-free, while the transmission spectra of HD 189733b and WASP-6b both indicate the presence of high altitude clouds or hazes. These observations further emphasize the surprising diversity of cloudy and cloud-free gas giant planets in short-period orbits and the corresponding challenges associated with developing predictive cloud models for these atmospheres.
KW - planetary systems
KW - planets and satellites: atmospheres
KW - stars: individual (WASP-39)
KW - techniques: spectroscopic
UR - https://www.scopus.com/pages/publications/84982104815
UR - https://www.scopus.com/pages/publications/84982104815#tab=citedBy
U2 - 10.3847/0004-637X/827/1/19
DO - 10.3847/0004-637X/827/1/19
M3 - Article
AN - SCOPUS:84982104815
SN - 0004-637X
VL - 827
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
M1 - 19
ER -