Clark, Benjamin Joseph Michael (2019) Follow-up observations and characterisation of transiting hot Jupiter exoplanets. Doctoral thesis, Keele University.

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The discovery of the first hot Jupiter exoplanet more than twenty years ago raised many questions. Such large, hot planets were not predicted to exist so close to their host star. Since then, more than 125 hot Jupiters have been discovered (to date), with a total of 3726 exoplanets detected. With well-refined discovery methods and future detection surveys such as TESS and PLATO set to provide a wealth of ideal planets to study, we can now begin to move towards characterisation of these planets through follow-up observations.
Working towards this goal, the aim of this thesis was to undertake such observations to refine planetary parameters, search for additional planetary companions and variations within the light curves and to probe the atmospheric structure and composition of hot Jupiters. To achieve this, general purpose pipelines were created for the calibration of images, to perform aperture photometry and to explore the impact that choices of comparison star and aperture size had on values of eclipse depth and the light curve quality. A new method was introduced to allow apertures to be placed centrally over a de-focused PSF in a time efficient way, and a new de-trending method was used to improve the quality of transit light curves produced from short cadence data of the K2 mission.
Thermal emission from the hot Jupiter WASP-48b was detected in the Ks-band using the 3.6 m Canada-France Hawaii Telescope. From the resulting occultation light curve a planet-to-star contrast ratio of 0:136 +- 0:014% was found which was in agreement with the value of 0:109 +- 0:027% that had been previously determined. From a global analysis, the system parameters were refined and a spectral energy distribution (SED) of the dayside atmosphere was constructed. Models with and without a thermal inversion were consistent with the data and the planet's orbit was found to be circular (e < 0:072 at 3?).
Short-cadence K2 data of two previously known hot Jupiter exoplanets were also analysed. The WASP-55b and WASP-75b K2 light curves offered a high enough precision to allow the data to be searched for transit timing and duration variations, rotational modulation, starspots, phase-curve variations and additional transiting planets. Stellar variability was identified in the WASP-75 light curve, which may be a possible indication of rotational modulation, with an estimated period of 11.2+-1.5 days and a possible line of sight projected inclination angle of i* = 41 +- 16?. A global analysis of the K2 and previously published data was performed and the system parameters were refined.
Spectro-photomery observations of two hot Jupiters, WASP 77Ab and WASP- 85Ab were analysed using the SINFONI instrument on the Very Large Telescope (VLT). The idea was to probe the day-side emission spectra of these planets by observing occultations at a higher resolution than broad-band photometry. However, observations were plagued with issues such as bad pixels and a lack of suitable comparison stars meaning poor quality light curves were produced. This combined with the stringent requirements needed for selected targets indicated that this particular instrument was not well-suited for these types of observation; an instrument with a wider field of view is necessary.
Overall, the work done in this thesis aimed to reduce the complexity and increase the reliability of these kinds of measurements. The routines created as part of this work are flexible enough to be applied to a broad range of data to provide high quality photometric measurements. The application of these to both space and ground based data produced light curves from which detailed analyses were obtained. They have the potential to be applied to a diverse number of observations, including large-scale surveys of occultation events which would allow a homogeneous analysis of exoplanet atmospheres.

Item Type: Thesis (Doctoral)
Subjects: Q Science > QB Astronomy > QB600 Planets. Planetology
Divisions: Faculty of Natural Sciences > School of Chemical and Physical Sciences
Contributors: Hellier, C (Thesis advisor)
Depositing User: Lisa Bailey
Date Deposited: 18 Mar 2019 16:12
Last Modified: 02 Sep 2020 14:32

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