Current Schedule

Speaker = Dr. Nicole Vassh of TRIUMF (Canada)

Host = Filomena Nunes nunes@frib.msu.edu

When = 2025-04-02 Wednesday

Where = FRIB 1300

Please feel free to sign up below, but note that some slots may need to be re-assigned to accommodate those with a specific need to meet the speaker. If this happens, the Admin or Speaker Host will reach out to you via email.

Title = Illuminating heavy element production using MeV gamma-rays and metal-poor stars

Abstract

Fingerprints of the properties of exotic nuclei on nucleosynthesis observables have been used for decades to frame our picture of how the heaviest elements in our Solar System came to be. The abundance of elements in our Sun, as well as nearby metal-poor stars, hints at multiple neutron capture nucleosynthesis processes, the slow (s), intermediate (i) and rapid ® neutron capture processes. While the s-process terminates its heavy element production at Pb-208, we know that the r-process or i-process must be capable of going beyond since we observe long-lived actinides like U-238 in stars and traces of Cm-247 in meteorites. However, which astrophysical site(s) are responsible for actinide production, and exactly how heavy each nucleosynthesis process can ultimately reach remains unclear. Utilizing metal-poor stars rich in r-process elements, we will explore recent work that has suggested signatures of fission fragments of isotopes with A~260 to be observed. I will also discuss a recent application of machine learning to decipher metal-poor star abundance patterns. Further, we will discuss the utility of MeV gamma-rays, in particular a 2.6 MeV emission line of Tl-208 that could be used to hunt locally for in situ neutron capture nucleosynthesis from both i-process and r-process sources. I will also discuss the opportunity to refine our understanding through measurements at radioactive isotope beam facilities in the near future, such as constraints on neutron captures along the Tl isotopic chain. It is via studies such as these, which work to combine the current picture of leading astrophysical candidates with carefully considered nuclear data, that the big picture of heavy element origins can be teased out.

Relevant background with commentary from Speaker:

• Our PRL from last year about the gamma rays emitted when Tl-208 is produced in astrophysical sites, link here: Thallium-208: A Beacon of In Situ Neutron Capture Nucleosynthesis - I will of course talk about more than Tl but it will be a main topic.