Between the lines Advancing exoplanet characterisation with high resolution cross-correlation spectroscopy

This thesis investigates a data analysis method known high-resolution cross-correlation spectroscopy (HRCCS), which since 2010 has proven to be a powerful and versatile tool for the characterisation of exoplanet atmospheres. This was done using data-sets from three canonical exoplanets: 51 Pegasi b, the first hot Jupiter and the first planet discovered around a main sequence star; HD 189773 b, a bright transiting hot Jupiter; and WASP-121 b, an extreme ultra hot Jupiter.
In Chapter 2 of this thesis, we sought a reflected light signal from the 51 Pegasi b. We further investigated the effect of rotational broadening on the 51 Pegasi system. Previous works had assumed that the impact of rotational broadening on the reflected light signal would be minimal for this system, however, we found that it was substantial.
In Chapter 3, we investigated the adaptation of the Sysrem algorithm to HRCCS analysis. We extensively reviewed the highly varied and non-uniform applications of the algorithm in the HRCCS literature. We then sought to determine which methods for applying Sysrem to HRCCS data-sets were both robust against the creation of false signals, and capable of well-detrending the data.
Finally, in Chapter 4, we presented a new suite of planet atmospheric models, which account for NLTE conditions. We then performed an analysis with a WASP-121 b transmission spectroscopy dataset, which exhibits an unexpectedly strong neutral iron spectral feature, using these models both as injected model signals and as cross-correlation templates.