The impact of nuclear and astrophysical uncertainties on utilizing Tl-208 as a real-time indicator of heavy element formation

Recent progress spurred by LIGO's detection of gravitational waves now leads us to examine kilonovae as crucial markers in unraveling the processes behind the synthesis of heavy elements in the Universe, such as the rapid (r) neutron capture process. The emission spectra of MeV gamma rays could lead to strong insight in the identification of individual isotopes if specific lines can be associated to specific isotopes. For example, the 2.6 MeV gamma-ray emission line from Tl-208 has been well known in various branches of science, but it has never been pointed out as a potential real-time indicator of heavy element production in an astrophysical context. In this talk, I will show that Tl-208 could be detectable ~12 hours to ~10 days, and again ~8 years following a Galactic neutron star merger, implying that the r process in such events is capable of synthesizing elements such as lead and gold. I will also talk about understanding the dependance of these calculations on nuclear physics uncertainties and astrophysical variations by including mass model, neutron richness, and equation of state variations. This is a strong argument for the importance of future MeV telescope missions aiming to detect Galactic events, but that may also be able to reach nearby galaxies in the Local Group.