Spectroscopic Properties of a Two-Dimensional Cepheid Model

Valeriy Vasilyev, Hans-Günter Ludwig, Bernd Freytag, Bertrand Lemasle and Marcella Marconi

The chemical composition of Cepheid variables can provide information on the chemo-dynamical evolution of the Galaxy and beyond. The standard method for determining atmospheric parameters and abundances of Cepheids is based on one-dimensional plane-parallel hydrostatic model atmospheres, where convection is treated by Mixing Length Theory. We check the validity of the quasi-static approach against a two-dimensional dynamical Cepheid model computed with CO5BOLD. The spectroscopic investigation of the two-dimensional Cepheid model allowed to derive projection factors and to explain the residual line-of-sight velocity of Galactic Cepheids, long known as the “K-term”, by line shifts of con- vective origin. Moreover, hydrostatic 1D model atmospheres can provide unbiased estimates of stellar parameters and abundances of Cepheids for particular phases of their pulsations.

Proceedings of the Polish Astronomical Society, vol. 6, 222-226 (2018)

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