UNC-CH Physics and Astronomy Thesis Proposal Presentation

Benjamin C Kaiser, Advisor; J Christopher Clemens

“Lithium Pollution of White Dwarfs as the Key to Resolving the Cosmological Lithium Problem”

Tidal disruption and subsequent accretion of planetesimals by white dwarfs can reveal the elemental abundances of rocky bodies in exoplanetary systems. Those abundances provide information on the composition of the nebula from which the systems formed and the geological processes that the rocky material experienced, which is analogous to how meteorite abundances inform our understanding of the Solar System. We recently performed the first identification of lithium and first identification of potassium in a white dwarf. We also performed the second identification of lithium in a white dwarf. An additional three white dwarfs have since been discovered to be polluted by lithium from extrasolar planetesimals. All five white dwarfs’ accreted extrasolar planetesimals have lithium levels higher than those of rocky material from the Solar System. We propose to interpret the abundances of these five white dwarfs to demonstrate geological processes are not adequate to explain the lithium overabundances in all extrasolar planetesimals with lithium detections. The abundances and relative ages of the systems support the apparent lithium overabundances resulting from the initial nebular abundances. We also propose to compare our results to predictions for Galactic nucleosynthetic enrichment models and the Big Bang nucleosynthetic predictions for lithium. This will lay the foundation for testing Big Bang nucleosynthetic lithium predictions and potentially resolving the Cosmological Lithium Problem. We also propose to present the results of the broader spectroscopic survey from which these results emerged. The survey is focused on the region of the H-R Diagram between the terminus of the white dwarf cooling sequence and the main sequence.

Presentation will be delivered in-person & via Zoom: https://unc.zoom.us/j/98768772980?pwd=WDlDeHpLUGVwNC9rbGdkbDVvNklYQT09