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Background     The Equations     Data feed     Numerical method     Compiling and running     Validation of the code


Data feed

The code needs a “picture” of a star at sometime t for which to calculate the eigenfunctions and eigenvalues of the oscillations, i.e. an input file. The code can work with two types of input files - MESA files and fgong files.

The MESA file:

MESA (Modules for Experiments in Stellar Astrophysics) is a suite of libraries for a wide range of applications in stellar astrophysics. It can be used to numerically evolve a star, for example, and so obtain many "pictures" of it at specific instances in time. You can download MESA from the MESA project website (mesa.sourceforge.net/). Notice that it cannot run on Windows! The website also provides instructions how to use the program. The "pictures" MESA generates are called profiles and they can be found in the working directory of the star you are currently running (after you actually run the code) under a directory called LOGS/. In general, the file name will be "profile#.data" where the number # corresponds to different times. These files can be used as input for my code.
If you plan to run MESA, pay attention to the following instructions, they are important for my code to run properly. If you don't feel like going through the trouble of running MESA, here and here are two examples of ready-to-use MESA output files. The first file is of a Red Giant which started its life with 9.5 solar masses and is currently burning helium in its core. The second file is of a massive star which started its life with 15 solar masses and is now burning oxygen in its core.

Profile data:

Before you run your stellar model in MESA you need to make sure that it would store certain information which is essential for this code to work. You do this by accessing the folder where you work on your star and opening the file “profile_columns.list”. Enable the following data by simply erasing the “!” in front of it :

  • gamma1
  • brunt_N2
    From here, run the the star as usual.

    Mesh points:

    For the code to work well, the star needs a proper resolution. About 2000 mesh points should suffice. If the model you ran has a smaller mesh than that, you can increase its size by changing the parameter - mesh_delta_coeff in the &controls section in the relevant inlist in your working directory. The rule is that cutting mesh_delta_coeff by half about doubles the number of mesh points. If this parameter doesn't already appear in your inlist just add the line:

    mesh\_delta\_coeff = your number here

    The default value is mesh_delta_coeff = 1. If MESA has trouble adjusting to the new value (e.g. it throws an error that it passed the maximum allowed number of mesh points), try increasing it little by little till the code runs smoothly.

    The fgong file:

    The GONG project (Global Oscillation Network Group) is a group that investigates the physics of the internal structure of our Sun and its dynamics. They have several detailed models for the Sun which provide an extensive set of variables describing its structure. The most extensively used model, called Model S, can be downloaded from the following link: Model S (just save the link). A detailed description of this model can be found in Christensen-Dalsgaard et al. (1996).
    Other models can be found in the following tar.gz file: models.for.n.tar.gz, where the relevant models are the fgong.something files (don't use the other files). The tar.gz file was obtained from here. To uncompress and open it, write in the command line: tar -zxvf models.for.n.tar.gz.


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