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Astron. Astrophys. 363, 568-574 (2000)


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Van Hoof effect between metallic lines in RR Lyrae

II. Comparison with purely radiative models

M. Chadid 1,2, D. Gillet 3 and A.B. Fokin 4

1 European Southern Observatory (ESO), Alonso de Cordova 3107, P.O. 19001, Santiago, Chile (mchadid@eso.org)
2 Observatoire de la Côte d'Azur, CNRS, Département A. Fresnel, B.P., 4229 Nice, France
3 Observatoire de Haute-Provence CNRS, 04870 Saint-Michel l'Observatoire, France (gillet@obs-hp.fr)
4 Institute for Astronomy of the Russia Academy of Sciences, 48 Pjatnitskaja, 109017 Moscow, Russia (fokin@inasan.rssi.ru)

Received 14 April 1999 / Accepted 20 March 2000

Abstract

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 (1997). These atmospheric models are purely radiative and are generated with a Lagrangean code. A comparison between theoretical velocities of two Fe I and Fe II 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.

Key words: hydrodynamics – shock waves – stars: individual: RR Lyr – stars: oscillations – stars: variables: RR Lyr


© European Southern Observatory (ESO) 2000

Online publication: December 11, 2000

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