Secondary eclipses of WASP-18b – near-infrared observations with the Anglo-Australian Telescope, the Magellan Clay Telescope and the LCOGT network
Article
Article Title | Secondary eclipses of WASP-18b – near-infrared observations with the Anglo-Australian Telescope, the Magellan Clay Telescope and the LCOGT network |
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ERA Journal ID | 1074 |
Article Category | Article |
Authors | Kedziora-Chudczer, L. (Author), Zhou, G. (Author), Bailey, J. (Author), Bayliss, D. D. R. (Author), Tinney, C. G. (Author), Osip, D. (Author), Colon, K. D. (Author), Shporer, A. (Author) and Dragomir, D. (Author) |
Journal Title | Monthly Notices of the Royal Astronomical Society |
Journal Citation | 483 (4), pp. 5110-5122 |
Number of Pages | 13 |
Year | 2018 |
Publisher | Oxford University Press |
Place of Publication | United Kingdom |
ISSN | 0035-8711 |
1365-2966 | |
Digital Object Identifier (DOI) | https://doi.org/10.1093/mnras/sty3381 |
Web Address (URL) | https://academic.oup.com/mnras/article/483/4/5110/5245188 |
Abstract | We present new eclipse observations for one of the hottest 'hot Jupiters', WASP-18b, for which previously published data from HST WFC3 and Spitzer have led to radically conflicting conclusions about the composition of this planet's atmosphere. We measure eclipse depths of 0.15± 0.02 per cent at Ks and 0.07± 0.01 per cent at z′ bands. Using the vstar line-by-line radiative transfer code and both these new observations with previously published data, we derive a new model of the planetary atmosphere. We have varied both the metallicity and C/O ratio in our modelling, and find no need for the extreme metallicity suggested by Sheppard et al. Our best-fitting models slightly underestimate the emission at z′ band and overestimate the observed flux at Ksband. To explain these discrepancies, we examine the impact on the planetary emission spectrum of the presence of several types of hazes which could form on the night side of the planet. Our Ks-band eclipse flux measurement is lower than expected from clear atmosphere models and this could be explained by haze particles larger than 0.2 μm with the optical properties of Al 2 O 3 , CaTiO 3 or MgSiO 3 . We find that z′-band measurements are important for understanding the contribution of photochemical hazes with particles smaller than 0.1 μm at the top of the atmosphere. |
Keywords | occultations; planets and satellites: atmospheres; planets and; satellites: individual: WASP-18b; Astrophysics - Earth and Planetary; Astrophysics |
ANZSRC Field of Research 2020 | 510109. Stellar astronomy and planetary systems |
Public Notes | This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2018 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. |
Byline Affiliations | University of New South Wales |
Center for Astrophysics Harvard and Smithsonian, United States | |
University of Warwick, United Kingdom | |
Carnegie Institution of Washington, United States | |
NASA Goddard Space Flight Center, United States | |
Massachusetts Institute of Technology, United States | |
Institution of Origin | University of Southern Queensland |
https://research.usq.edu.au/item/q6x48/secondary-eclipses-of-wasp-18b-near-infrared-observations-with-the-anglo-australian-telescope-the-magellan-clay-telescope-and-the-lcogt-network
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