WASP-127b transmission spectrum]{Abundance measurements of H$_{2}$O and carbon-bearing species in the atmosphere of WASP-127b confirm its super-solar metallicity. (arXiv:1911.08859v2 [astro-ph.EP] UPDATED)

WASP-127b transmission spectrum]{Abundance measurements of H$_{2}$O and carbon-bearing species in the atmosphere of WASP-127b confirm its super-solar metallicity. (arXiv:1911.08859v2 [astro-ph.EP] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Spake_J/0/1/0/all/0/1">Jessica J. Spake</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sing_D/0/1/0/all/0/1">David K. Sing</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wakeford_H/0/1/0/all/0/1">Hannah R. Wakeford</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nikolov_N/0/1/0/all/0/1">Nikolay Nikolov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mikal_Evans_T/0/1/0/all/0/1">Thomas Mikal-Evans</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Deming_D/0/1/0/all/0/1">Drake Deming</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Barstow_J/0/1/0/all/0/1">Joanna K. Barstow</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Anderson_D/0/1/0/all/0/1">David R. Anderson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Carter_A/0/1/0/all/0/1">Aarynn L. Carter</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gillon_M/0/1/0/all/0/1">Michael Gillon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Goyal_J/0/1/0/all/0/1">Jayesh M. Goyal</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hebrard_G/0/1/0/all/0/1">Guillaume Hebrard</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hellier_C/0/1/0/all/0/1">Coel Hellier</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kataria_T/0/1/0/all/0/1">Tiffany Kataria</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lam_K/0/1/0/all/0/1">Kristine W. F. Lam</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Triaud_A/0/1/0/all/0/1">A. H. M. J. Triaud</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wheatley_P/0/1/0/all/0/1">Peter J. Wheatley</a>

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 $mu$m), using the Hubble and Spitzer Space Telescopes. Our results show a
feature-rich transmission spectrum, with absorption from Na, H$_{2}$O, and
CO$_{2}$, 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 super-solar, 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 super-solar CO$_{2}$ volume mixing ratios, which adds to the
likelihood that WASP-127b’s bulk metallicity is super-solar, since CO$_{2}$
abundance is highly sensitive to atmospheric metallicity. We detect water at a
significance of 13.7 $sigma$. 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 JWST will be able to constrain WASP-127b’s C/O ratio,
and may reveal the formation history of this metal-enriched, highly observable
exoplanet.

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