SIMBAD references

The differential motion between the photospheric layers of RR Lyrae, where the metallic absorption lines are formed, is calculated with nonlinear nonadiabatic pulsating models recently published by Fokin & Gillet (1997A&A...325.1013F). These atmospheric models are purely radiative and are generated with a Lagrangean code. A comparison between theoretical velocities of two FeI and FeII unblended lines shows important differences from the observations around the minimum radius, i.e. when strong shock waves emerge from the photosphere. An analysis of the models indicates that the inadequate modelling of large gradients occurring during this phase interval, is the main disadvantage of this type of models. A complete interpretation of the high quality observations needs the use of more elaborate atmospheric pulsating models.