LRG-BEASTS: transmission spectroscopy and retrieval analysis of the highly-inflated Saturn-mass planet WASP-39b
| Autor: | Ian Skillen, Mercedes Lopez-Morales, Néstor Espinoza, James McCormac, Peter J. Wheatley, Ian C. Weaver, Tom Louden, James Kirk |
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| Jazyk: | angličtina |
| Rok vydání: | 2019 |
| Předmět: |
Earth and Planetary Astrophysics (astro-ph.EP)
Physics 010504 meteorology & atmospheric sciences Metallicity FOS: Physical sciences Astronomy and Astrophysics Scale height Astrophysics 01 natural sciences Exoplanet Space and Planetary Science Planet Saturn 0103 physical sciences Orders of magnitude (length) William Herschel Telescope Transit (astronomy) 010303 astronomy & astrophysics 0105 earth and related environmental sciences Astrophysics - Earth and Planetary Astrophysics |
| Zdroj: | The Astronomical Journal |
| Popis: | We present a ground-based transmission spectrum and comprehensive retrieval analysis of the highly inflated Saturn-mass planet WASP-39b. We obtained low-resolution spectra ($R \approx 400$) of a transit of WASP-39b using the ACAM instrument on the 4.2m William Herschel Telescope as part of the LRG-BEASTS survey. Our transmission spectrum is in good agreement with previous ground- and space-based observations of WASP-39b, and covers a wavelength range of 4000-9000A. Previous analyses of this exoplanet have retrieved water abundances that span more than four orders of magnitude, which in turn lead to conclusions of a subsolar or highly supersolar atmospheric metallicity. In order to determine the cause of the large discrepancies in the literature regarding WASP-39b's atmospheric metallicity, we performed retrieval analyses of all literature data sets. Our retrievals, which assume equilibrium chemistry, recovered highly supersolar metallicities for all data sets. When running our retrievals on a combined spectrum, spanning 0.3-5$\mu$m, we recovered an atmospheric metallicity of $282^{+65}_{-58} \times$ solar. We find that stellar activity has a negligible effect on the derived abundances and instead conclude that different assumptions made during retrieval analyses lead to the reported water abundances that differ by orders of magnitude. This in turn has significant consequences for the conclusions we draw. This is the fourth planet to be observed as part of the LRG-BEASTS survey, which is demonstrating that 4m class telescopes can obtain low-resolution transmission spectra with precisions of around one atmospheric scale height. Comment: Final journal proof version. 21 pages, 9 figures, 6 tables |
| Databáze: | OpenAIRE |
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