techniques: spectroscopic; planets and satellites: atmospheres; stars: individual: WASP-127; Astrophysics - Earth and Planetary Astrophysics
Abstract :
[en] 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[SUB]J[/SUB]), sub-Saturn mass (0.19 M[SUB]J[/SUB]) 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, H[SUB]2[/SUB]O, and CO[SUB]2[/SUB], 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 CO[SUB]2[/SUB] volume mixing ratios, which adds to the likelihood that WASP-127b's bulk metallicity is supersolar, since CO[SUB]2[/SUB] 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.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Spake, Jessica J.; Physics and Astronomy, University of Exeter, Stocker Road, Exeter EX4 3RF, UK
Sing, David K.; Physics and Astronomy, University of Exeter, Stocker Road, Exeter EX4 3RF, UK
Wakeford, Hannah R.; School of Physics, HH Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, UK
Nikolov, Nikolay; Space Telescope Science Institute, 3700 San Martin Dr, Baltimore, MD 21218, USA
Mikal-Evans, Thomas; Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, 37-241, Cambridge, MA 02139, USA
Deming, Drake; Department of Astronomy, University of Maryland, College Park, MD 20742, USA
Barstow, Joanna K.; School of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
Anderson, David R.; Astrophysics Group, Keele University, Staffordshire ST5 5BG, UK
Carter, Aarynn L.; Physics and Astronomy, University of Exeter, Stocker Road, Exeter EX4 3RF, UK
Gillon, Michaël ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Exotic
Goyal, Jayesh M.; Department of Astronomy and Carl Sagan Institute, Cornell University, 122 Sciences Drive, Ithaca, NY 14853, USA
Hebrard, Guillaume; Sorbonne Universite, CNRS, UMR 7095, Institut d'Astrophysique de Paris, 98 bis bd Arago, F-75014 Paris, France
Hellier, Coel; Astrophysics Group, Keele University, Staffordshire ST5 5BG, UK
Kataria, Tiffany; NASA Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
Lam, Kristine W. F.; Center for Astronomy and Astrophysics, Technical University Berlin, Hardenbergstr. 36, D-10623 Berlin, Germany
Triaud, A. H. M. J.; School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
Wheatley, Peter J.; Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK)
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