Abstract
The nuclide \( _{75} ^{187}Re\) β‾ -decays to \( _{76} ^{187}Os\) with a half-life of approximately 41.6 Gyr. The long half-life and simple relation between \( _{75} ^{187}Re\) and \( _{76} ^{187}Os\) makes the ratio a good candidate for a cosmic clock. In order to "use the clock" we must determine the production of \( _{75} ^{187}Re\) and \( _{76} ^{187}Os\) through chemical enrichment of the Galaxy. This is a complicated task with a large number of assumptions and simplifications involved. The uncertainties related to some of the uncertainties are investigated.
A hydrodynamical simulation is approximated with a simple one-zone chemical evolution model. The physical parameters of the chemical evolution model is varied by generating random numbers with a Gaussian distribution to emulate the uncertainty of parameters.
I conclude that observational constraints on r-process nuclei does not affect the cosmochronology of the Re-Os system much. The Galactic history, like star formation and mass function over time, would have greater effect on the cosmochronology.
Veileder: Førsteamanuensis Sijing Shen, Institutt for teoretisk astrofysikk, UiO
Medveileder: Postdoktor Signe Riemer-Sørensen, Institutt for teroretisk astrofysikk, UiO
Intern sensor: Professor Øystein Elgarøy, Institutt for teoretisk astrofysikk, UiO
Ekstern sensor: Associate Professor, Christa Gall, Dark Cosmology Centre, University of Copenhagen.