Frequency ratio method for seismic modelling of gamma Doradus stars. II. The role of rotation
Résumé
The effect of rotation on the Frequency Ratio Method (Moya et al. 2005, A&A, 432, 189) is examined. Its applicability to observed frequencies of rotating gamma Doradus stars is discussed taking into account the following aspects: the use of a perturbative approach to compute adiabatic oscillation frequencies; the effect of rotation on the observational Brunt-Väisälä integral determination and finally, the problem of disentangling multiplet-like structures from frequency patterns due to the period spacing expected for high-order gravity modes in asymptotic regime. This analysis reveals that the FRM produces reliable results for objects with rotational velocities up to 70 {km s-1}, for which the FRM intrinsic error increases one order of magnitude with respect to the typical FRM errors given in Moya et al. (2005, A&A, 432, 189). Our computations suggest that, given the spherical degree l identification, the FRM may be discriminating for m=0 modes, in the sense that the method avoids any misinterpretation induced by the presence of rotationally split multiplet-like structures, which reinforces the robustness of the method. However, if l is unknown, such discrimination is not ensured. In order to check the FRM in presence of slow-moderate rotation, we have applied it to the three observed frequencies of the slowly rotating ({v sin i}=29 {km s-1}) gamma Doradus star HD 48501.