Chemical trends in Hot Jupiter atmospheres

Braam, Marrick (2020) Chemical trends in Hot Jupiter atmospheres. Master's Thesis / Essay, Astronomy.

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Abstract

Exoplanetary science has entered the era of comparative characterisation of giant planet atmospheres, providing valuable insights into planetary conditions and their formation and migration histories. We investigate the possible existence of chemical trends in Hot Jupiter atmospheres, by comparatively analysing transmission spectra of 17 planets with varying coverage from 0.3-4.5µm (HST and Spitzer) using the Bayesian retrieval framework TauREx II. A statistically significant signature of H2O is found for 11 of the planets, with at least 2.2σ confidence. Additionally, there are detections of the signatures of VO (2 planets), TiO (2), AlO (2), Na (5), K (5) and particle scattering (3). The first tentative hints towards the signatures of OH were found in WASP-19b. Furthermore, WASP-39b shows tentative evidence for CrH absorption, whereas the CrH signatures are clearly seen in WASP-31b at ~4σ. As a first trend, retrieved water abundances seem to decrease with temperature, contrary to expectations from thermal equilibrium chemistry. These disequilibrium abundances may be (partly) caused by photochemical processes since lower abundances are retrieved for planets receiving higher estimated UV irradiation. Planetary abundance ratios are found to be both stellar and substellar, indicating different formation histories. The enhanced wavelength coverage of JWST may further disclose abundance trends by providing improved estimates on the C/O ratio and understanding of clouds/hazes.

Item Type:	Thesis (Master's Thesis / Essay)
Supervisor name:	Tak, F.F.S. van der
Degree programme:	Astronomy
Thesis type:	Master's Thesis / Essay
Language:	English
Date Deposited:	27 Jul 2020 13:47
Last Modified:	27 Jul 2020 13:47
URI:	https://fse.studenttheses.ub.rug.nl/id/eprint/22721

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