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Solar-to-supersolar sodium and oxygen absolute abundances for a "hot Saturn" orbiting a metal-rich star

We present new analysis of infrared transmission spectroscopy of the cloud-free hot-Saturn WASP-96b performed with the Hubble and Spitzer Space Telescopes (HST and Spitzer). The WASP-96b spectrum exhibits the absorption feature from water in excellent agreement with synthetic spectra computed assumi...

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Bibliographic Details
Published in:arXiv.org 2022-05
Main Authors: Nikolov, Nikolay K, Sing, David K, Spake, Jessica J, Smalley, Barry, Goyal, Jayesh M, Mikal-Evans, Thomas, Wakeford, Hannah R, Rustamkulov, Zafar, Drake Deming, tney, Jonathan J, Carter, Aarynn, Gibson, Neale P, Mayne, Nathan J
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Language:English
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Summary:We present new analysis of infrared transmission spectroscopy of the cloud-free hot-Saturn WASP-96b performed with the Hubble and Spitzer Space Telescopes (HST and Spitzer). The WASP-96b spectrum exhibits the absorption feature from water in excellent agreement with synthetic spectra computed assuming a cloud-free atmosphere. The HST-Spitzer spectrum is coupled with Very Large Telescope (VLT) optical transmission spectroscopy which reveals the full pressure-broadened profile of the sodium absorption feature and enables the derivation of absolute abundances. We confirm and correct for a spectral offset of \(\Delta R_{{\rm p}}/R_{\ast}=(-4.29^{+0.31}_{-0.37})\,\times10^{-3}\) of the VLT data relative to the HST-Spitzer spectrum. This offset can be explained by the assumed radius for the common-mode correction of the VLT spectra, which is a well-known feature of ground-based transmission spectroscopy. We find evidence for a lack of chromospheric and photometric activity of the host star which, therefore, make a negligible contribution to the offset. We measure abundances for Na and O that are consistent with solar to supersolar, with abundances relative to solar values of \(21^{+27}_{-14}\) and \(7^{+11}_{-4}\), respectively. We complement the transmission spectrum with new thermal emission constraints from Spitzer observations at 3.6 and \(4.5\mu\)m, which are best explained by the spectrum of an atmosphere with a temperature decreasing with altitude. A fit to the spectrum assuming an isothermal blackbody atmosphere constrains the dayside temperature to be \(T_{\rm{p}}\)=$1545$$\pm$$90$K.
ISSN:2331-8422
DOI:10.48550/arxiv.2206.00017