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Doctoral Defense

April 11, 2023 @ 3:00 pm - 4:30 pm

Stellar associations – groups of coeval, co-moving stars – are fundamental to our understanding of stellar ages and critical for the study of stellar and planetary evolution. All stellar age measurements, with the sole exception of the Sun, are based on the ages of stellar associations or on methods developed through studies of associations. Young associations in particular provide excellent benchmarks to study stellar and planetary evolution, as many important evolutionary steps occur during the first billion years of a star’s existence.

The combination of the Gaia, Kepler, and TESS missions have ushered in a golden age for studying stellar and planetary evolution. These studies will require both robust, accurate age measurements for stellar associations and numerous planets within those associations to study.

However, commonly used methods of measuring age, such as isochrone fitting, are imprecise and depend strongly on poorly-understood physical parameters such as magnetic fields. An alternative, more precise way to achieve association ages, the Lithium Depletion Boundary (LDB) method is less model-dependent but requires observationally expensive spectra of low-mass association members. Moreover, less than one hundred young (<1 Gyr) planets have yet been discovered, offering few vantage points into a highly important and dynamic time period.

In this thesis I characterize several nearby, planet-hosting associations and planets within them. I clarify the associations’ membership and kinematics using 6D astrometric data available from the Gaia mission, and the BANYAN tool for association membership. I measure the ages of the associations using the LDB method and spectra obtained on the Goodman HTS on the SOAR telescope. When possible these ages are confirmed using additional age-measurement methods, making the resulting ages robust and accurate. The products of this thesis are new ages and membership lists for several previously known associations and subpopulations (Musca, LCC-A, LCC-B, LCC-C, Carina, Theia 92, Theia 113), the discovery and characterization of an entirely new association (MELANGE-4), and the discovery or confirmation of three exoplanets within those associations. Collectively, the associations studied here contain thousands of stars and 7 known planets, forming an impressive sample of accurately age-dated stars and planets on which future studies can rely.

Mackenna Wood

I will be presenting my thesis titled “Lithium Depletion Boundary Ages of Young, Planet-Hosting Stellar Associations”.

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April 11, 2023
3:00 pm - 4:30 pm


Phillips 277