Disentangling the effects of spotty stars from exoplanet atmosphere observation

Lead Research Organisation: The Open University
Department Name: Faculty of Sci, Tech, Eng & Maths (STEM)

Abstract

My interest in astronomy is deep set. From a young age I developed a fascination with the stars that
eventually evolved into an enthusiasm for exoplanets where the sheer variety of planetary systems captured
and held my interest for many years. At every possible moment throughout my education, I grasped at
opportunities to learn more about astronomy, from taking extra astronomy modules in my undergraduate
degree, to choosing an exoplanet based research project for my masters, and ultimately adopting a career
that allowed me to write about the latest astronomical research. I have a passion for space and a drive for
research that I feel would serve me well in a PhD position.
I have good amount of research experience so far, consisting of a year-long self-led Masters project on
the phase curves of non-transiting exoplanets and an undergraduate research project focused on MHD
structures in the solar wind.
The aim of my Masters project was to identify candidate systems for non-transiting planets. To do
this, I used data from years 1 and 3 of the TESS mission to analyse light signals from target stars in
the southern hemisphere that have the potential to show a large amplitude phase curve. Using Python,
I constructed a pipeline to search for phase curves signals of three effects: tidal ellipsoidal distortion,
atmospheric modulation, and Doppler beaming. With this pipeline, I compiled a list of systems that are
candidate hosts for short-period, giant exoplanets and applied a visual assessment of the light curve and
aperture to each star in the list. The remaining 34 candidates were modelled using three superimposed
sine curves corresponding to the phase curve components, representing systems with the potential to host
non-transiting planets. These systems are now being followed up with data from HARPS and CHEOPS. I
am currently in the process of publishing a paper on my findings in a peer reviewed journal as first author.
For my work on this project, I was awarded the Warwick thesis prize in 2023. The prize recognised my
dedication to the project and the 'outstanding standard of work' in my thesis.
In this project, I improved on my programming skills with regular use of python and Unix commands.
I also gained experience in writing reports, project proposals and overviews, and contributed towards a
presentation for the PLATO atmospheres workshop. Through regular group meetings and seminars, I
expanded my knowledge of key astronomical principles across a wide range of topics including planetary
atmospheres, structures and habitability.
In my third year at Warwick, I undertook a research project in the Centre for Fusion, Space and
Astrophysics using data from ESA's Cluster mission. During this project, I studied magnetohydrodynamic
theories in order to construct a magnetic field gradient tensor and investigate the topology of magnetic
field structures in turbulent solar wind. This lead to observations on the interactions between the plasma
flow, the magnetic field topology and the rate of Ohmic heating outside the Earth's influence. I developed
a data analysis tool in MATLAB to determine which structures dominate the solar magnetic field on a
given scale and if these structures are actively evolving. This consolidated my passion and enthusiasm for
research, leading me to undertake a Masters by Research the following year.
My passion for astronomy extends beyond research. In my free time, I read popular and newly released
astronomy books, reviewing them for Physics World Magazine. Alongside regular monitoring of new journal
papers, this helps me to stay updated with recent advancements in the field, deepen my knowledge of wider
astronomy topics, and make new connections with astronomers across the globe

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
ST/Y509449/1 30/09/2023 29/09/2028
2928801 Studentship ST/Y509449/1 30/09/2024 31/12/2027 Caitlyn Cullen