Sensitivity of the Calculated g-Mode Frequencies to Pulsation Codes and their Parameters

Abstract

From the recent work of the Evolution and Seismic Tools Activity (ESTA: Monteiro et al., ESA, SP-1306, 363 – 371, 2006 and Lebreton et al., Astrophys. Space Sci. 316, 1 – 12, 2008), whose Task 2 is devoted to comparing pulsational frequencies computed using most of the pulsational codes available in the asteroseismic community, the dependence of the theoretical frequencies on non-physical choices is now quite well specified. To ensure that the accuracy of the computed frequencies is of the same order of magnitude or better than the observational errors, some requirements in the equilibrium models and the numerical resolutions of the pulsational equations must be followed. In particular, we have verified the numerical accuracy obtained with the Saclay seismic model, which is used to study the solar g-mode region (60 to 140 μHz). We have compared the results coming from the Aarhus adiabatic pulsation code (ADIPLS), with the frequencies computed with the Granada Code (GraCo) taking into account several possible non-physical choices and the effect of using two different outer mechanical boundary conditions. We have concluded that the present equilibrium models and the use of the Richardson extrapolation ensure an accuracy of the order of 0.01 μHz in the determination of the frequencies, which is quite enough for our purposes.