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

Nikolov, Nikolay K. and Sing, David K. and Spake, Jessica J. and Smalley, Barry and Goyal, Jayesh M. and Mikal-Evans, Thomas and Wakeford, Hannah R. and Rustamkulov, Zafar and Deming, Drake and Fortney, Jonathan J. and Carter, Aarynn and Gibson, Neale P. and Mayne, Nathan J. (2022) Solar-to-supersolar sodium and oxygen absolute abundances for a 'hot Saturn' orbiting a metal-rich star. Monthly Notices of the Royal Astronomical Society, 515 (2). pp. 3037-3058. ISSN 0035-8711. doi:10.1093/mnras/stac1530.

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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})\, \times 10^{-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 \mum, 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 Tp = 1545 ± 90 K.

Item Type:Article
Related URLs:
URLURL TypeDescription
Nikolov, Nikolay K.0000-0002-6500-3574
Sing, David K.0000-0001-6050-7645
Spake, Jessica J.0000-0002-5547-3775
Smalley, Barry0000-0002-3456-087X
Goyal, Jayesh M.0000-0002-8515-7204
Mikal-Evans, Thomas0000-0001-5442-1300
Wakeford, Hannah R.0000-0003-4328-3867
Rustamkulov, Zafar0000-0003-4408-0463
Deming, Drake0000-0001-5727-4094
Fortney, Jonathan J.0000-0002-9843-4354
Carter, Aarynn0000-0001-5365-4815
Gibson, Neale P.0000-0002-9308-2353
Mayne, Nathan J.0000-0001-6707-4563
Additional Information:Some/all of the data presented in this paper were obtained from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX13AC07G and by other grants and contracts. This work is based on observations with the NASA/ESA Hubble Space Telescope (GO-15469, Nikolov et al. 2018c), obtained at the Space Telescope Science Institute (STScI) operated by AURA, Inc. This work is based on observations made with the Spitzer Space Telescope (Nikolov et al. 2019), which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Based on observations collected at the European Southern Observatory under ESO programme 199.C-0467(H). This paper includes data collected by the TESS mission, which are publicly available from the Mikulski Archive for Space Telescopes (MAST). Funding for the TESS mission is provided by NASA’s Science Mission directorate. This research has made use of the VizieR catalogue access tool, CDS, Strasbourg, France. The authors are grateful to the anonymous referee for their thoughtful comments and suggestions, which helped to improve the manuscript. NN acknowledges support for this work by NASA through grants under the HST-GO-15469 program from the STScI. The research leading to these results received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement number 336792. JMG and NJM acknowledge support from a Leverhulme Trust Research Project Grant. This work used the Python Gaussian process library George. NM acknowledges funding from the UKRI Future Leaders Scheme (MR/T040866/1), Science and Technology Facilities Council Consolidated Grant (ST/R000395/1), and Leverhulme Trust research project grant (RPG-2020-82). ALC is supported by a grant from STScI (JWST-ERS-01386) under NASA contract NAS5-03127.
Funding AgencyGrant Number
European Research Council (ERC)336792
Leverhulme TrustRPG-2020-82
UK Research and InnovationMR/T040866/1
Science and Technology Facilities Council (STFC)ST/R000395/1
Space Telescope Science InstituteJWST-ERS-01386
Issue or Number:2
Record Number:CaltechAUTHORS:20220823-627526100
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:116417
Deposited By: Melissa Ray
Deposited On:30 Aug 2022 16:27
Last Modified:30 Aug 2022 16:27

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