Ph.D. University of Warwick (2019)
I study binary systems of various kinds, with the goal of finding empirical constraints on binary stellar evolutionary processes. Around half of the stars in the sky are in binary (or higher order) systems, and the interactions that these systems will undergo are important for many areas of astrophysics -- yet, many of these processes remain poorly understood from a theoretical perspective and poorly constrained from an observational perspective.
I am particularly interested in mass-transferring double white dwarf binary systems, in which a high-mass white dwarf strips material from the atmosphere of a lower-mass white dwarf. These include the most compact binaries known (with orbital periods down to 5 minutes) and offer a window into a region of binary stellar evolution which has many poorly understood aspects (common envelope evolution, magnetic braking, helium detonation...). By measuring properties such as their masses, radii, orbital periods, and their gravitational-wave driven period evolution, I hope to better understand how these systems form, and provide constraints on some of the open questions in binary stellar evolution.
I also have interests in short-period main sequence binaries. I used TESS to assemble a large sample of Solar-type binary systems at the very shortest periods (3 days or less), which are detected by their tidal deformation (so-called "ellipsoidal variability"). Using this sample, we were able to comment on the formation of binaries at these short periods and on the impacts of magnetic braking, third-body interactions and in-disc migration.
Lastly, I led a search for dormant (non-accreting) black hole companions to main sequence stars, using the same ellipsoidal variability technique. While the search did not yield any black holes, we were able to place an upper limit on the occurrence rate of black hole companions in very tight orbits -- which would be the progenitors of X-ray binaries. Our upper limit is comparable to the upper limit on black hole companions in wider orbits that has been found from astrometric searches.
