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Larivière, Maude

University of British Columbia

The question of how elements were formed across the Universe’s history remains the central question that nuclear astrophysics tries to answer. While processes in the core of stars are enough to explain the formation of elements up to iron, the synthesis of heavier elements is thought to rely on neutron capture processes, such as the rapid neutron capture process (r process). The sites responsible for the r process are still actively investigated, but neutron star mergers were confirmed as a site in 2017 with the detection of GW170817 and its associated kilonova. With LIGO set to observe more events, finding ways to probe neutron star merger ejecta composition is becoming more pressing. Identifications of individual isotopes via their emission spectra, notably through their gamma-ray emissions following nuclear decays, provides an interesting solution. This thesis explores the MeV gamma-rays from the 𝛽-decays of isotopes after their synthesis in neutron star mergers and highlights the thallium-208 (Tl-208) 2.6 MeV gamma-ray line as a real-time signal to probe the reach of the r process in neutron star mergers. It shows that Tl-208 produces a signal that could be detectable at three distinct timescales, ∼12 hours, ∼4 days, and ∼8 years for a Galactic neutron star merger. This signal currently represents the only known real-time signal that would directly point to lead production, which would also indicate gold synthesis. This supports the importance of future MeV telescope missions aiming to observe Galactic events or remnants, as well as signals from nearby galaxies such as those in the Local Group.

Text

2024-09-04

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/89158

Physics

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/