Towards Atmospheric Characterisation of Exoplanets
Abstract
This thesis provides a multi-pronged approach towards paving the way for future space
and ground based exoplanet characterisation e↵orts as well as providing new analysis
of the atmosphere of the exoplanet HD 179949 b. This is done, firstly, by outlining
engineering trade studies conducted for the attitude and orbit control system (AOCS)
and sun shield for the Exoplanet Characterisation Observatory (EChO) spacecraft (a
proposed European Space Agency exoplanet space mission). These trade studies were
conducted in collaboration with EADS Astrium. A cold gas system with the possibility
of a hybrid system which would include the use of reaction wheels is recommend for the
design of the AOCS. For the sun shield, a V-groove cone shield is concluded to provide
the best thermal coverage while also providing stay light protection as well as being
more mechanically symmetric than other options. Simulations are then conducted
to determine the number of transiting planets future surveys should expect to find
around stars within 50 parsecs of the sun. This is done by taking the known stars
within 50 parsecs and adding a simulated planet population based on current models
and observations to each star. Assumptions are made regarding observability of a
planetary transit and a Monte Carlo simulation run to gain statistics on the number
and type of planetary systems that can be expected to be found. The results of the
simulation show a mean expected number of 27 detectable transiting planets within 50
parsecs. Next, using the Position and Proper Motion Extended-L (PPMXL) catalogue,
optical and near-infrared colour cuts were used together with a reduced proper motion
cut to find bright M dwarfs for future exoplanet transit studies. PPMXL’s low proper
motion uncertainties allow this work to probe down to smaller proper motions than
previous similar studies. Unique objects found with this method were combined with
that of previous work to produce 8479 K < 9 M dwarfs. Low-resolution spectroscopy
was obtained of a sample of the objects found using this selection method to gain statistics on their spectral type and physical properties. Results show a spectral-type
range of K7-M4V. This catalogue is the most complete collection of K < 9 M dwarfs
currently available and is made available here. High resolution spectroscopy and model
spectra of planetary atmospheres is then used along with a spectral deconvolution
technique to attempt to detect the Doppler shifted signal of the non-transiting planet
HD 179949 b. The signal was not detected but new upper limits were set ruling out the
presence of TiO down to a log10 ✏0 = -4.09 with 99.9 per cent confidence. Simulations
conducted by this work imply a loss of sensitivity occurring possibly due to varying
telluric interference or instrumental systematics.
Publication date
2014-04-02Published version
https://doi.org/10.18745/th.14247https://doi.org/10.18745/th.14247