| Online-Ressource |
Verfasst von: | Vasilyev, Valeriy [VerfasserIn]  |
| Ludwig, Hans-Günter [VerfasserIn]  |
| Lemasle, Bertrand [VerfasserIn]  |
Titel: | Spectroscopic properties of a two-dimensional time-dependent Cepheid model |
Titelzusatz: | I. Description and validation of the model |
Verf.angabe: | V. Vasilyev, H.-G. Ludwig, B. Freytag, B. Lemasle, and M. Marconi |
E-Jahr: | 2017 |
Jahr: | 25 October 2017 |
Umfang: | 13 S. |
Fussnoten: | Gesehen am 12.01.2021 |
Titel Quelle: | Enthalten in: Astronomy and astrophysics |
Ort Quelle: | Les Ulis : EDP Sciences, 1969 |
Jahr Quelle: | 2017 |
Band/Heft Quelle: | 606(2017) Artikel-Nummer A140, 13 Seiten |
ISSN Quelle: | 1432-0746 |
Abstract: | Standard spectroscopic analyses of Cepheid variables are based on hydrostatic one-dimensional model atmospheres, with convection treated using various formulations of mixing-length theory.<i>Aims. <i/>This paper aims to carry out an investigation of the validity of the quasi-static approximation in the context of pulsating stars. We check the adequacy of a two-dimensional time-dependent model of a Cepheid-like variable with focus on its spectroscopic properties. <i>Methods. <i/>With the radiation-hydrodynamics code CO5BOLD, we construct a two-dimensional time-dependent envelope model of a Cepheid with <i>T<i/><sub>eff<sub/> = 5600 K, log <i>g<i/> = 2.0, solar metallicity, and a 2.8-day pulsation period. Subsequently, we perform extensive spectral syntheses of a set of artificial iron lines in local thermodynamic equilibrium. The set of lines allows us to systematically study effects of line strength, ionization stage, and excitation potential.<i>Results. <i/>We evaluate the microturbulent velocity, line asymmetry, projection factor, and Doppler shifts. The microturbulent velocity, averaged over all lines, depends on the pulsational phase and varies between 1.5 and 2.7 km s<sup>-1<sup/>. The derived projection factor lies between 1.23 and 1.27, which agrees with observational results. The mean Doppler shift is non-zero and negative, −1 km s<sup>-1<sup/>, after averaging over several full periods and lines. This residual line-of-sight velocity (related to the “K-term”) is primarily caused by horizontal inhomogeneities, and consequently we interpret it as the familiar convective blueshift ubiquitously present in non-pulsating late-type stars. Limited statistics prevent firm conclusions on the line asymmetries.<i>Conclusions. <i/>Our two-dimensional model provides a reasonably accurate representation of the spectroscopic properties of a short-period Cepheid-like variable star. Some properties are primarily controlled by convective inhomogeneities rather than by the Cepheid-defining pulsations. Extended multi-dimensional modelling offers new insight into the nature of pulsating stars. |
DOI: | doi:10.1051/0004-6361/201731422 |
URL: | Bitte beachten Sie: Dies ist ein Bibliographieeintrag. Ein Volltextzugriff für Mitglieder der Universität besteht hier nur, falls für die entsprechende Zeitschrift/den entsprechenden Sammelband ein Abonnement besteht oder es sich um einen OpenAccess-Titel handelt.
Kostenfrei: Volltext ; Verlag: http://dx.doi.org/10.1051/0004-6361/201731422 |
| Kostenfrei: Volltext: https://www.aanda.org/articles/aa/abs/2017/10/aa31422-17/aa31422-17.html |
| DOI: https://doi.org/10.1051/0004-6361/201731422 |
Datenträger: | Online-Ressource |
Sprache: | eng |
K10plus-PPN: | 1571413545 |
Verknüpfungen: | → Zeitschrift |
Spectroscopic properties of a two-dimensional time-dependent Cepheid model / Vasilyev, Valeriy [VerfasserIn]; 25 October 2017 (Online-Ressource)