Keegan Thomson-Paressant

Searching for Hot Jupiters with Kepler K2 - Fall 2015

Supervisor: Prof. Michael Ireland, Australian National University

During this short, 6 month research project, a colleague and I worked with M. Ireland to determine the continued viability of the Kepler satellite for detecting exoplanets after having broken two of its reaction wheels. Labelled the Kepler K2 mission, we used a number of programming and transit spectroscopy skills to generate a new data reduction pipeline for the K2 data. The easiest targets to detect were Hot Jupiters, large planets orbiting in very close proximity to their parent star, due to their significant transit depths and short orbital period. The team proposed a number of candidates requiring follow-up radial velocity observations.

Hydrogen and Carbon Radio Recombination Lines in the W3 Starforming Region - 2017-2018

Supervisors: Prof. Alexander Tielens, Leiden University, Dr. Raymond Oonk, Leiden University

Under the tutelage of my supervisors, we observed the W3 starforming region at 1.4 GHz using the APERTIF upgrade on the Westerbork Synthesis Radio Telescope. The goal was to analyse the hydrogen and carbon emission coming from the W3 complex on both large and small scales. To this end, a full data reduction suite was performed on the APERTIF radio data to uncover the recombination lines hidden within. Once completed the results could be compared with past work, such as that of the Effelsberg-Bonn HI Survey (EBHIS), to determine the distribution of the emission. It was determined that there is quite a significant disparity in what was observed by APERTIF on small scales, revealing the existence of quite a complex region, versus what EBHIS saw in the broader picture. 

Detecting Exoplanets with TESS and MASCARA - 2018-2019

Supervisors: Prof. Ignas Snellen, Leiden University, Dr. Aurélien Wyttenbach, Leiden University

With the Transiting Exoplanet Survey Satellite (TESS) having recently come out of beta testing, there were already quite a number of potential transiting exoplanet candidates requiring follow-up observations. It was this hole that the Multi-site All-Sky CAmeRA (MASCARA) hoped to fill. The project was split into two sections, with my colleague R. Wang performing follow-ups of candidates brighter than apparent magnitude of 8.4 (the theoretical limit of MASCARA), and myself following up targets between 8.4 and about 10 apparent magnitude. Using the accurate TESS information as a guide, data reduction processes were performed on the MASCARA data to recover the transit signal seen by TESS. Simulations of 10,000 transits were also performed, in order to calculate theoretical limits of the MASCARA instrument within our magnitude range and determine a family of "ideal" candidates for future follow-up observations.

Magnetism in Delta Scuti Variable Stars - 2020-2024

Supervisor: Dr. Coralie Neiner, Paris Observatory

Delta Scuti stars (δ Sct) are intermediate mass stars that present pulsations and brightness variations lasting anywhere from a few minutes to several hours. Until recently, only a handful of these stars have been shown to host magnetic fields, and amongst them their characteristics vary greatly. While it isn't entirely clear how the magnetic fields interact with the pulsations, what is certain is that there appears to be an underrepresentation of magnetic candidates within this family of stars. While about 10% of typical intermediate mass stars present some kind of magnetic field, the percentage for δ Sct stars appears to be below that, which begs the question of why that might be. 

We perform spectropolarimetric analysis on a sample of these stars, using data primarily from the NeoNarval (TBL) and ESPaDOnS (CFHT) instruments, in an attempt to identify additional magnetic candidates, characterise their magnetic fields, model their field structure at the surface, and finally theorise as to their origin. 

Thans to efforts made during my PhD, we have achieved a list containing 13 confirmed magnetic δ Sct, from which initial statistical analyses have been performed. Most notably, we have demonstrated the first observational evidence of the shift of an instability region as a direct result of the presence of a (strong) magnetic field. 

High differential astrometry of binary systems using GRAVITY - 2020-2022

Supervisors: Dr. Pierre Kervella, Paris Observatory; Dr. Antoine Mérand, ESO Garching

We performed high resolution differential astrometry of binary sysems, using the GRAVITY instrument operating on the Very Large Telescope Interferometer (VLTI) in Chile, and measuring the minute deviations from their expected orbits that would result from hidden mass within the system, such as a planet orbiting one of the stars. We studied a number of such systems, with particular emphasis on GJ65 and Alpha Centauri.

The Alpha Centauri (α Cen) system is composed of three stars: 2 Sun-like stars (α Cen A and B) in a binary pair and an M-dwarf (Proxima Cen) that orbits the pair at some distance. At the time of the project, 3 exoplanets had been confirmed around Proxima, though none yet had been detected around the A or B components. Studies suggest that stable orbits exist around either star, including their theoretical habitable zones. Combining this with the fact that they are the closest stars to Earth, as well as potential analogs to our own Solar System, make them appealing targets for exoplanetary investigation. 

Between the proximity of the α Cen system to our own, resulting in brightness issues, combined with the fact that GRAVITY wasn't originally designed to observe this type of object, resulted in us being required to resolve a number of unique challenges in order to properly exploit the data and achieve the precision required to detect exoplanets.