Stellar and Galactic Archaeology
Binary Systems
When using chemically peculiar stars to explore nucleosynthesis events, an important question is whether the unusual pattern resulted from mass transfer from a binary companion. I have led several long-term radial-velocity monitoring programs, determining the binary frequency of chemically peculiar stars. My current program is focused on the CEMP-r/s stars, which might bear the signature of an i-process.
Picture of the 2.7m telescope at McDonald Observatory in west Texas. Extensively used for my binary program.
Classical Dwarf Galaxies
Analysis of large samples of metal-poor stars in the Milky Way halo has revealed chemical signatures that remain unexplained. One of these is the large fraction of carbon-
enhanced stars found at low metallicity (CEMP stars)
Recent exploration of classical dwarf galaxies reveals similar trends in C abundance. This suggests that C enhancement is a defining characteristic of all metal-poor stellar populations, independent of the environment. Below is a Figure from Hansen et al. (2023) showing the absolute carbon abundances of CEMP stars in Dwarf Galaxies.
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