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A new utility to study strong chemical gradients in stellar interiors

Stefano R. García Castañeda

The asymptotic analysis of the pulsation equations predicts regularly-spaced periods for gravity modes. These periods get deflected when a sharp variation in the buoyancy frequency, associated with strong chemical gradients, is present. These features are known as glitches and their study is one of the few methods allowing us to probe the physical conditions in a localized region inside a star. Theoretical works (e.g., Cunha et al. 2015, 2019) provide the analytical bases to interpret the signatures of glitches of arbitrary amplitude in seismic observables. However, testing the analytical predictions is not straightforward, because finding a model with a glitch with specific properties (e.g., position, amplitude, and width) implies, in the best-case scenario, to explore the space of stellar parameters until the desired glitch is attained. This approach has clear disadvantages like (1) no warranty to generate the pursued glitch, (2) time consuming, and (3) preclusion of a direct comparison of the effect of different glitches on the seismic data.
Here, we present a program that allows to artificially add/remove a Gaussian-like glitch into/from the buoyancy profile of an already existing stellar model, that way solving points (1-3). Comparison between the sharpness of the glitch with respect to the local wavelength of gravity modes is also provided. The modification to the buoyancy frequency is done in a consistent way by a correspondent modification of the first adiabatic exponent as described in Ball et al. 2018. The program counts with an interactive GUI as well as a command line mode and is available as a Github repository.

2019 July 17, 13:30

Centro de Astrofísica da Universidade do Porto (Classroom)
Rua das Estrelas, 4150-762 Porto

Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia