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Author (up) Carone, L.; Molliere, P.; Zhou, YF.; Bouwman, J.; Yan, F.; Baeyens, R.; Apai, D.; Espinoza, N.; Rackham, BV.; Jordan, A.; Angerhausen, D.; Decin, L.; Lendl, M.; Venot, O.; Henning, T.
Title Indications for very high metallicity and absence of methane in the eccentric exo-Saturn WASP-117b Type
Year 2021 Publication Astronomy & Astrophysics Abbreviated Journal Astron. Astrophys.
Volume 646 Issue Pages A168
Keywords methods: observational; planets and satellites: atmospheres
Abstract Aims. We investigate the atmospheric composition of the long-period (P-orb = 10 days) eccentric exo-Saturn WASP-117b. WASP-117b could be similar in atmospheric temperature and chemistry to WASP-107b. In mass and radius, WASP-117b is similar to WASP-39b, which allows a comparative study of these planets.Methods. We analyzed a near-infrared transmission spectrum of WASP-117b taken with the Hubble Space Telescope (HST) WFC3 G141, which was reduced with two independent pipelines. High-resolution measurements were taken with VLT/ESPRESSO in the optical.Results. We report the robust (3 sigma) detection of a water spectral feature. In a 1D atmosphere model with isothermal temperature, uniform cloud deck, and equilibrium chemistry, the Bayesian evidence of a retrieval analysis of the transmission spectrum indicates a preference for a high atmospheric metallicity

[Fe/H] = 2.58(-0.37)(+0.26)

[Fe/H]=2.58-0.37+0.26 and clear skies. The data are also consistent with a lower metallicity composition [Fe/H] < 1.75 and a cloud deck between 10(-2.2) and 10(-5.1) bar, but with weaker Bayesian preference. We retrieve a low CH4 abundance of <10(-4) volume fraction within 1 sigma and <2 x 10(-1) volume fraction within 3<sigma>. We cannot constrain the equilibrium temperature between theoretically imposed limits of 700 and 1000 K. Further observations are needed to confirm quenching of CH4 with K-zz >= 10(8) cm(2) s(-1). We report indications of Na and K in the VLT/ESPRESSO high-resolution spectrum with substantial Bayesian evidence in combination with HST data.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0004-6361 ISBN Medium
Area Expedition Conference
Notes WOS:000624484900001 Approved
Call Number UAI @ alexi.delcanto @ Serial 1353
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Author (up) Weaver, IC.; Lopez-Morales, M.; Alam, MK.; Espinoza, N.; Rackham, BV.; Goyal, JM.; MacDonald, RJ.; Lewis, NK.; Apai, D.; Bixel, A.; Jordan, A.; Kirk, J.; McGruder, C.; Osip, DJ.
Title ACCESS: An Optical Transmission Spectrum of the High-gravity Hot Jupiter HAT-P-23b Type
Year 2021 Publication Astronomical Journal Abbreviated Journal Astron. J.
Volume 161 Issue 6 Pages 278
Keywords EXOPLANET HD 189733B; HST PANCET PROGRAM; EXTRASOLAR PLANET; CLOUDY ATMOSPHERE; CLEAR ATMOSPHERE; GIANT PLANET; WATER-VAPOR; GAS GIANT; SPECTROSCOPY; HUBBLE
Abstract We present a new ground-based visible transmission spectrum of the high-gravity, hot Jupiter HAT-P-23b, obtained as part of the ACCESS project. We derive the spectrum from five transits observed between 2016 and 2018, with combined wavelength coverage between 5200 angstrom and 9269 angstrom in 200 angstrom bins, and with a median precision of 247 ppm per bin. HAT-P-23b's relatively high surface gravity (g approximate to 30 m s(-2)), combined with updated stellar and planetary parameters from Gaia DR2, gives a five-scale-height signal of 384 ppm for a hydrogen-dominated atmosphere. Bayesian models favor a clear atmosphere for the planet with the tentative presence of TiO, after simultaneously modeling stellar contamination, using spots parameter constraints from photometry. If confirmed, HAT-P-23b would be the first example of a high-gravity gas giant with a clear atmosphere observed in transmission at optical/near-IR wavelengths; therefore, we recommend expanding observations to the UV and IR to confirm our results and further characterize this planet. This result demonstrates how combining transmission spectroscopy of exoplanet atmospheres with long-term photometric monitoring of the host stars can help disentangle the exoplanet and stellar activity signals.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0004-6256 ISBN Medium
Area Expedition Conference
Notes WOS:000655343200001 Approved
Call Number UAI @ alexi.delcanto @ Serial 1396
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