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Abundance measurements of H₂O and carbon-bearing species in the atmosphere of WASP-127b confirm its supersolar metallicity

Spake, Jessica J. and Sing, David K. and Wakeford, Hannah R. and Nikolov, Nikolay and Mikal-Evans, Thomas and Deming, Drake and Barstow, Joanna K. and Anderson, David R. and Carter, Aarynn L. and Gillon, Michaël and Goyal, Jayesh M. and Hebrard, Guillaume and Hellier, Coel and Kataria, Tiffany and Lam, Kristine W. F. and Triaud, A. H. M. J. and Wheatley, Peter J. (2021) Abundance measurements of H₂O and carbon-bearing species in the atmosphere of WASP-127b confirm its supersolar metallicity. Monthly Notices of the Royal Astronomical Society, 500 (3). pp. 4042-4064. ISSN 0035-8711.

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The chemical abundances of exoplanet atmospheres may provide valuable information about the bulk compositions, formation pathways, and evolutionary histories of planets. Exoplanets with large, relatively cloud-free atmospheres, and which orbit bright stars provide the best opportunities for accurate abundance measurements. For this reason, we measured the transmission spectrum of the bright (V ∼ 10.2), large (1.37 R_J), sub-Saturn mass (0.19 M_J) exoplanet WASP-127b across the near-UV to near-infrared wavelength range (0.3–5 μm), using the Hubble and Spitzer Space Telescopes. Our results show a feature-rich transmission spectrum, with absorption from Na, H₂O, and CO₂, and wavelength-dependent scattering from small-particle condensates. We ran two types of atmospheric retrieval models: one enforcing chemical equilibrium, and the other which fit the abundances freely. Our retrieved abundances at chemical equilibrium for Na, O, and C are all supersolar, with abundances relative to solar values of 9⁺¹⁵₋₆⁠, 16⁺⁷₋₅⁠, and 26⁺¹²₋₉⁠, respectively. Despite giving conflicting C/O ratios, both retrievals gave supersolar CO₂ volume mixing ratios, which adds to the likelihood that WASP-127b’s bulk metallicity is supersolar, since CO₂ abundance is highly sensitive to atmospheric metallicity. We detect water at a significance of 13.7σ. Our detection of Na is in agreement with previous ground-based detections, though we find a much lower abundance, and we also do not find evidence for Li or K despite increased sensitivity. In the future, spectroscopy with James Webb Space Telescope will be able to constrain WASP-127b’s C/O ratio, and may reveal the formation history of this metal-enriched, highly observable exoplanet.

Item Type:Article
Related URLs:
URLURL TypeDescription
https://archive.stsci.eduRelated ItemMikulski Archive for Space Telescopes ItemNASA/IPAC Infrared Science Archive
Spake, Jessica J.0000-0002-5547-3775
Sing, David K.0000-0001-6050-7645
Wakeford, Hannah R.0000-0003-4328-3867
Nikolov, Nikolay0000-0002-6500-3574
Mikal-Evans, Thomas0000-0001-5442-1300
Deming, Drake0000-0001-5727-4094
Barstow, Joanna K.0000-0003-3726-5419
Anderson, David R.0000-0001-7416-7522
Carter, Aarynn L.0000-0001-5365-4815
Gillon, Michaël0000-0003-1462-7739
Goyal, Jayesh M.0000-0002-8515-7204
Kataria, Tiffany0000-0003-3759-9080
Triaud, A. H. M. J.0000-0002-5510-8751
Wheatley, Peter J.0000-0003-1452-2240
Alternate Title:Abundance measurements of H2O and carbon-bearing species in the atmosphere of WASP-127b confirm its supersolar metallicity
Additional Information:© 2020 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2020 September 3. Received 2020 August 7; in original form 2019 November 19. Published: 13 October 2020. This work is based on observations made with the NASA/European Space Acency Hubble Space Telescope that were obtained at the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy, Inc. Support for this work was provided by NASA through grants under the HST-GO-14619 program from the STScI. A portion of this work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. ALC is funded by a UK Science and Technology Facilities (STFC) studentship. This work made use of the PYTHON package CORNER (Foreman-Mackey 2016). JJS thanks the anonymous reviewer for productive comments. Data Availability: Raw HST data frames are publicly available online at the Mikulski Archive for Space Telescopes (MAST; Raw Spitzer data frames are publicly available at the NASA/IPAC Infrared Science Archive (IRSA;
Funding AgencyGrant Number
Science and Technology Facilities Council (STFC)UNSPECIFIED
Subject Keywords:techniques: spectroscopic – planets and satellites: atmospheres – stars: individual: WASP-127
Issue or Number:3
Record Number:CaltechAUTHORS:20210208-122718508
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Official Citation:Jessica J Spake, David K Sing, Hannah R Wakeford, Nikolay Nikolov, Thomas Mikal-Evans, Drake Deming, Joanna K Barstow, David R Anderson, Aarynn L Carter, Michael Gillon, Jayesh M Goyal, Guillaume Hebrard, Coel Hellier, Tiffany Kataria, Kristine W F Lam, A H M J Triaud, Peter J Wheatley, Abundance measurements of H2O and carbon-bearing species in the atmosphere of WASP-127b confirm its supersolar metallicity, Monthly Notices of the Royal Astronomical Society, Volume 500, Issue 3, January 2021, Pages 4042–4064,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:107949
Deposited By: Tony Diaz
Deposited On:08 Feb 2021 20:43
Last Modified:08 Feb 2021 20:43

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