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Natalie Rees (Surrey)

Computing a Grid of Asymptotic Giant Branch Stars
When Dec 16, 2021
from 03:30 PM to 03:45 PM
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Asymptotic Giant Branch (AGB) stars are important contributors to galactic chemical evolution due to their unique nucleosynthesis, which occurs as a result of the thermal pulses and is consequently blown from their surfaces in strong stellar winds. They are considered to be major producers of carbon, nitrogen and of elements heavier than iron by the s-process. However, AGB stars are notoriously difficult to model with full stellar evolution codes, such as MESA, due to the various instabilities and convergence issues that arise during the thermal pulses. This makes the production of grids of AGB stars, with varying masses and metallicities, time consuming due to the large amount of human debugging required. This talk will summarise the various instabilities and convergence found using MESA and discuss ways to evolve past them, such that a grid of AGB models can be reliably run without intervention. From the full models, data will be extracted and transformed into a tabulated grid for use in the population synthesis code binary_c. Populations of stars can then be run through the AGB phase by interpolating parameters from the tabulated grid. These populations will have various uses including calculations of chemical yields and the ability to constrain stellar physics, such as convection, by comparison to observations.