English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Standard spectroscopic analyses of Cepheid variables are based on hydrostaticone-dimensional model atmospheres, with convection treated using variousformulations of mixing-length theory. This paper aims to carry out aninvestigation of the validity of the quasi-static approximation in the contextof pulsating stars. We check the adequacy of a two-dimensional time-dependentmodel of a Cepheid-like variable with focus on its spectroscopic properties.With the radiation-hydrodynamics code CO5BOLD, we construct a two-dimensionaltime-dependent envelope model of a Cepheid with $T_\mathrm{eff}= 5600$ K, $\logg=2.0$, solar metallicity, and a 2.8-day pulsation period. Subsequently, weperform extensive spectral syntheses of a set of artificial iron lines in localthermodynamic equilibrium. The set of lines allows us to systematically studyeffects of line strength, ionization stage, and excitation potential. Weevaluate the microturbulent velocity, line asymmetry, projection factor, andDoppler shifts. The mean Doppler shift is non-zero and negative, -1 km/s, afteraveraging over several full periods and lines. This residual line-of-sightvelocity (related to the "K-term") is primarily caused by horizontalinhomogeneities, and consequently we interpret it as the familiar convectiveblueshift ubiquitously present in non-pulsating late-type stars. Limitedstatistics prevent firm conclusions on the line asymmetries. Ourtwo-dimensional model provides a reasonably accurate representation of thespectroscopic properties of a short-period Cepheid-like variable star. Someproperties are primarily controlled by convective inhomogeneities rather thanby the Cepheid-defining pulsations.

Spectroscopic properties of a two-dimensional time-dependent Cepheid model I. Description and validation of the model