2026 Theses Doctoral

Rebels of the Night Sky: Studying Anomalous Stellar Populations with Spectroscopy and Asteroseismology

Sayeed, Maryum

The Milky Way’s history is encoded in the observed properties of its stars. Unusual stellar populations are particularly important, since they can skew our interpretation of the Galaxy’s evolution as well as the occurrence rate of exoplanets. Fully understanding stellar evolution and correcting for biases from anomalous stellar populations in stellar models is crucial in accurately capturing the Galaxy’s history. However, the role of environmental effects versus stellar evolution theory in the formation of these objects is still unclear. To disentangle signatures of nature versus nurture, the tools of spectroscopy and asteroseismology are a powerful means to trace a star’s evolution, capturing signatures of external pollution as well as details of its internal structure.

My thesis aims to investigate the formation pathways for two unusual stellar populations: lithium-rich red giants and non-oscillating stars using astrometry, spectroscopic, and photometric data from ongoing ground-based and space-based missions. My research has revealed that (i) multiple channels create lithium-rich red giants, including binarity, and (ii) that stellar activity suppresses oscillation amplitudes. Uncovering the origin of peculiar stellar populations provides the foundation for interpreting the chemical and structural diversity of the Milky Way.