I am a post-doctoral research fellow in the Astronomy and Astrophysics group at the University of Warwick, working with Pier-Emmanuel Tremblay in the white dwarf group. I use white dwarfs as a cosmic laboratory to dissect planetary material, uncovering the formation histories of rocky bodies from other planetary systems.

Research Interests

Over the last 30 years, astronomy has been propelled into a new era by the discovery and characterisation of thousands of exoplanets (planets orbiting stars other than the Sun). Of particular interest is the search for Earth-like planets. One of the key characteristics of Earth is its geological composition, which ultimately affects its internal structure, tectonic behaviour and atmosphere. However, it is difficult to determine whether exoplanets are made of the same material as Earth because, in general, a broad range of compositions could be consistent with the data.

Nature provides an unlikely solution in the form of dead stars called white dwarfs. These objects sometimes accrete the remains of their own planetary systems, which leads to detectable quantities of planetary material entering the white dwarf's atmosphere. By analysing the spectra of these so-called "polluted" white dwarfs, it is possible to measure the relative abundances of different elements in the planetary material.

My research focuses on the interpretation of white dwarf pollution, based on the measured elemental abundances. I am interested in deducing the geology and history of rocky bodies, including whether they show evidence of iron core formation, how far away they formed from their star, and whether they might have had water. I am also interested in tackling various effects which must be taken into account during this interpretation. For example, the physics of the white dwarf atmosphere can distort the detected relative elemental abundances away from their true values. I am currently investigating how different models of the white dwarf's atmosphere can alter the inferred geology.

Much of my research makes use of the open source code PyllutedWD. Currently, I am the sole developer and maintainer of this code.

Publications

• Buchan A. M., Bonsor A., Rogers L. K., Brouwers M. G., Shorttle O., Tremblay P., 2024, White dwarf constraints on geological processes at the population level, MNRAS, 532, 2705‑2723
• Rogers L. K., Bonsor A., Xu S., Buchan A. M., Dufour P., Klein B. L., Hodgkin, S., Kissler‑Patig M., Melis C., Walton C., Weinberger A., 2024, Seven white dwarfs with circumstellar gas discs II: tracing the composition of exoplanetary building blocks, MNRAS, 532, 3866‑3880
• Rogers L. K., Bonsor A., Xu S., Dufour P., Klein B. L., Buchan A. M., Hodgkin, S., Hardy F., Kissler‑Patig M., Melis C., Weinberger A., Zuckerman B., 2024, Seven white dwarfs with circumstellar gas discs I: white dwarf parameters and accreted planetary abundances, MNRAS, 527, 6038‑6054
• Buchan A. M., 2023, Exogeology as Revealed by Polluted White Dwarfs, PhD thesis, Apollo ‑ University of Cambridge Repository
• Bonsor A., Lichtenberg T., Dra̧żkowska J., Buchan A. M., 2023, Rapid formation of exoplanetesimals revealed by white dwarfs, Nature Astronomy, 7, 39‑48
• Brouwers M. G., Buchan A. M., Bonsor A., Malamud U., Lynch E., Rogers L., 2022, Asynchronous accretion can mimic diverse white dwarf pollutants II: water content, MNRAS, 519, 2663‑2679
• Buchan A. M., Bonsor A., Shorttle O., Wade J., Harrison J., Noack L., Koester D., 2022, Planets or asteroids? A geochemical method to constrain the masses of White Dwarf pollutants, MNRAS, 510, 3512‑3530
• Harrison J. H. D., Bonsor A., Kama M., Buchan A. M., Blouin S., Koester D., 2021, Bayesian constraints on the origin and geology of exoplanetary material using a population of externally polluted white dwarfs, MNRAS, 504, 2853–2867