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Introducing StORM: a fast stellar oscillation code including the effects of rotational deformation

Vanlaer, Vincent

Publisher
Zenodo
DOI
10.5281/zenodo.17242935
Repository
zenodo.org
Language
en

Abstract

The field of asteroseismology is built upon tools to compute theoretical stellar pulsation frequencies, of which GYRE is a well known example. However, publicly available tools do not support all the necessary features to model the wealth of data that we have available. A prime example is the effect of stellar deformation due to fast rotation on the pulsation frequencies. Furthermore, as stellar modelling becomes more data driven and large grids of stellar models become the norm, performance of the oscillation code in terms of precision and computational speed becomes more and more important. Stellar Oscillations with Rotation and Magnetism (StORM) is a novelstellar oscillation code developed to treat these challenges. I will give an overview of the capabilities of StORM and some applications, with a particular focus on the effects of rotation and stellar deformation. In its current form, StORM is at least ten times faster than GYRE. StORM will be available under an open source license, with an extensive documentation.

Full text

Get notified of release stellar-oscillations.org Use case large model grids asymmetric multiplets This work is supported by the Research Foundation Flanders (FWO) under grant agreements 1156925N (PhD fellowship) and K233724N (travel grant) Vincent Vanlaer PhD student @ Institute of Astronomy, KU Leuven [email protected] Performance of different order collocation methods in StORM and GYRE. 8th order collocation is not provided by GYRE. Ran on a single core laptop CPU for a 6200 point stellar model. This test was limited to radial modes, and in total 19 modes were found. Performance is does not depend on the particular type of star, only on the number of model points. Rotation causes stellar deformation, which changes the size of the oscillation cavities of stars, and couples modes of different degrees. This plot shows an example of the effect of stellar deformation on mode frequencies. Note the coupling between the radial mode and the zonal quadrupole mode, which causes the frequencies to appear to bounce of each other. The stucture and the radial oscillation frequencies of an index-0 polytrope have analytical expressions. Hence, tests of index-0 polytropes can be used to perform convergence testing of oscillation codes. Here, we find that all methods converge at the expected rate, up to the machine precision (~10-16). StORM vs. analytical solution of polytrope Order of convergence Convergence test Deformation: strong frequency deviationsStORM is 10x to 70x faster than GYRE Frequency differences between StORM and GYRE for a 6200 point stellar model. The main reason for these differences is interpolation of the stellar model, which is implemented differently in each of the codes. Including more grid points in the stellar model will decrease the difference, including less grid points will increase it. Typical theoretical model uncertainties are much larger than these differences. Relative difference StORM & GYRE: 10-5 to 10-6 Order of convergence