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Title: Ground and space-based transit surveys : exoplanet detection and evaporating atmospheres
Author: Lam, Wai Fun
ISNI:       0000 0004 7972 414X
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2018
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The characteristics and dynamics of exoplanets are broad and diverse. Detailed analysis of the systems can shed light on the history of their formation and evolution. This thesis presents the discovery and analysis of a range of exoplanets. The evaporating planet WASP-12 b was studied to understand the evolution of its atmosphere. Further, the investigation of a new planet detection method through measuring the stellar activity index is presented. Three gas giant planets were detected by SuperWASP. The inflated Neptune WASP- 127 b is one of the least dense planets detected to date. It has a striking atmospheric scale height of 2500 km, which provides an optimal target for atmospheric studies with the James Webb Space Telescope. The hot Jupiter WASP-136 b was found to be in a re-inflation phase as its host star is evolving, and the planet is predicted to have an age of 0:420 Gyr. The detection of WASP-138 b around a slightly metal-poor host weakens the correlation between formation of planets and the metallicity of stars. In addition to ground-based discoveries, the super-Earth EPIC 206011496 b was detected with the K2 mission. The mass of EPIC 206011496 b was determined with HARPS RV with a precision of 13%. The bulk density of the planet implies an Earth-like composition which has a predominantly rocky interior. EPIC 206011496 b lies at the lower limit of the photoevaporation gap, which suggests its atmosphere may have been eroded away in the past. The variability of the evaporating hot Jupiter WASP-12 b was investigated using archival KECK/HIRES spectra. Enhanced absorption in the cores of both Ca ii H and K and Na i D lines were detected throughout the planetary orbit, supporting the presence of a circumstellar gas disc formed by the evaporated planet material. The mean column density of Ca ii was measured as 6x1014 cm-2, which indicates an overall circumstellar gas density of 5:83 x 10-14 g cm-3. Inspired by the anomalously low activity index of a number of planet hosting stars, a survey was conducted to test a new detection technique which measures the activity index of stars in open clusters. An activity-age relation was determined for young mid-A to F type stars. Although no planet hosting candidate was identified, a significant increase in the sample size can ascertain the feasibility of this detection method.
Supervisor: Not available Sponsor: Science and Technology Facilities Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QC Physics