Astrophysics with Radioactive Isotopes

Constraining r-process nucleosynthesis using $^{129}$I and $^{247}$Cm in the early Solar system

Not scheduled

20m

Oral Presentation

Speaker

Dr Projjwal Banerjee (Indian Institute of Technology Palakkad)

Description

A recent study by Côté et al. (2021) has shown that ratio of the observed abundances of short-lived radioisotopes $^{129}$I and $^{247}$Cm in the early solar system (ESS), that are almost exclusively produced by r-process, can be used to directly constrain the "last" r-process source that contributed before the formation of the Solar system due to fact that these two isotopes have almost identical half-lives. This conclusion is critically based on the result that the $^{129}$I and $^{247}$Cm in the ESS come from one single r-process event. We study the evolution of $^{129}$I and $^{247}$Cm along with reference isotopes $^{127}$I and $^{235}$U at the Solar location using the turbulent gas diffusion formalism. We find that when 2-3 different r-process sources that are equally frequent but have distinct $^{129}$I/$^{247}$Cm production ratios are considered, the $^{129}$I and $^{247}$Cm in the ESS do not come entirely from a single major event but get contributions from at least two more minor contributors. This has a dramatic effect on the evolution of the $^{129}$I/$^{247}$Cm ratio, such that the measured ESS value in meteorites does not necessarily correspond to that of the "last" major r-process event and consequently cannot be used to constrain it. We also find that the requirement of concordance of the observed $^{129}$I/$^{127}$I and $^{247}$Cm/$^{235}$U ratio in the ESS has a major impact on the distribution of the $^{129}$I/$^{247}$Cm ratio in the ESS. We find that when the concordance criteria is taken into account, important constraints on the properties of r-process sources that were operating during the formation of the Solar system can still be made using the observed value of $^{129}$I/$^{247}$Cm ratio in the ESS.