Table of Contents
Exercise #0
Purpose
The objective of excercise-0 is to assess how far we are (the current oscillation codes) from ESTA/CoRoT exercise's conclusions. We want to set the basis on which the following exercises will be based.
Procedure
Step 1. The team computes the oscillations of the models</fc>. Considering ESTA/CoRoT conclusions, for this exercise we follow the following prescriptions:
- Only p-modes (up to cut-off frequency) (L=0,1,2,3)
- With and without Richardson Extrapolation
- Limit (surface) conditions: ρ → 0 and P → 0
- Universal gravitation constant G: please, specify wether you (1) read it from the model or (2) set it in the oscillation code (and provide value)
output files names: <fc #008080>nameofthefile-CodeNameCodeVer-[No]RichRo[P].your_extension</fc> CodeNameVer example: <fc #008080>FILOU3_20_0 (code FILOU, version 3.20.0)</fc>
Step 2. Analysis of the results</fc>. I will make a first comparison of the frequencies and seismic indices, and we will discuss the results by email and/or teleconference (if needed).
Step 3. Presentation of result & technical note</fc>. We will write a Technical Note for the PLATO consortium, and present the results at some PW and/or WP121 meeting.
The models
For this first exercise we will only consider five models of two different masses (1.04 and 1.5 Msun) and evolutionary stages (main sequence and sub-giant) and other two models from the BasTI grid (website here).
| Download : models wiki page |
|---|
Following ESTA/CoRoT experience, these quite different (and critical) internal structures (the presence of a convective core, and the chemical gradients present in evolved stars), would be - let's say - the worst case of study.
| GARSTEC models | |||||||
|---|---|---|---|---|---|---|---|
| Model | Mass | [Fe/H] | alpha | ovsh | Nshell | Phase | Notes |
| 0-001 | 1.04 | +0.05 | 1.6 | 0.00 | 3000 | MS | Representative of 16Cyg ~7Gyr (Travis et al. 2015) |
| 0-002 | 1.04 | +0.05 | 1.6 | 0.00 | 4000 | SG | - |
| 0-003 | 1.50 | +0.00 | 1.6 | 0.00 | 3000 | MS | Small convective core (around 8% of the stellar mass) |
| 0-004 | 1.50 | +0.00 | 1.6 | 0.00 | 4000 | TAMS | - |
| 0-005 | 1.50 | +0.00 | 1.6 | 0.00 | 4000 | SG | - |
| BaSTI models | |||||||
| b-001 | 1.00 | -0.08 | 1.6 | 0.00 | 1314 | MS | Taken directly from BaSTI online HR utility |
| b-002 | 1.00 | -0.08 | 1.6 | 0.00 | 1719 | SG | Taken directly from BaSTI online HR utility |
Discussion
- Note on BaSTI models: the number of shell points is already under those proposed by ESTA/CoRoT to be suitable for oscillation computation by using Richardson extrapolation. Even with re-meshing these numbers are too low. To be checked.
Conclusions
The main conclusion is that oscillation frequencies computed by XX,YY,ZZ, KK are similar within the range found in CoRoT/ESTA exercises (between 0.05 and 0.2 muHz) for individual frequencies and around 0.1-0.3 for large/small separations (TBV); the largest variations (up to 1-2 muHz in some cases) were due to the different boundary conditions used for the oscillation computation.
We considered that no further investigation on such differences were necessary since the critical tests are to be done with physically-consistent models (mainly hydrostatic equilibrium, Brunt-Vaisala frequency mapping and maybe EOS proper integration with the numerical scheme).
We concluded that we should focus on test with consistent models, starting by the standard solar model (model S by JCD).