Showing papers by "F. Thévenin published in 2006"
TL;DR: In this paper, a 3D hydrodynamical radiative transfer model of the atmosphere of the nearby dwarf star α Cen B (K1 V) was used to fit the new interferometric visibility measurements.
Abstract: For the nearby dwarf star α Cen B (K1 V), we present limb-darkening predictions from a 3D hydrodynamical radiative transfer model of its atmosphere. We first compared the results of this model to a standard Kurucz's atmosphere. Then we used both predictions to fit the new interferometric visibility measurements of α Cen B obtained with the VINCI instrument of the VLT Interferometer. Part of these new visibility measurements were obtained in the second lobe of the visibility function, which is sensitive to stellar limb-darkening. The best agreement is found for the 3D atmosphere limb-darkening model and a limb-darkened angular diameter of θ 3D = 6.000 ± 0.021 mas, corresponding to a linear radius of 0.863 ± 0.003 R (assuming π = 747.1 ± 1.2 mas). Our new linear radius agrees well with the asteroseismic value predicted by Thevenin et al. (2002, A&A, 392, L9). In view of future observations of this star with the VLTI/AMBER instrument, we also present limb-darkening predictions in the J, H, and K bands.
73 citations
TL;DR: In this paper, a detailed investigation of the validity of oscillator strengths in the spectral domain of the Gaia spectrometer 848-875 nm was performed by fitting the most significant Fe I and Si I solar lines in this spectral range with synthetic profiles calculated by 3D radiative hydrodynamical (RHD) simulations.
Abstract: This paper presents the results of a detailed investigation of the validity of oscillator strengths in the spectral domain of the Gaia spectrometer 848-875 nm. This analysis is performed by fitting the most significant Fe I and Si I solar lines in this spectral range with synthetic profiles calculated by 3D radiative hydrodynamical (RHD) simulations. Our main conclusion is that the laboratory oscillator strengths agree well (< 0.1 dex) with values derived from 3D simulations, whereas the semi-empirical values found in data bases like the Vienna Atomic Line Database are imprecise, with a disagreement that can be as large as 1 dex. We address this conclusion to laboratories to encourage new oscillator strength measurements in the infrared, especially in the Gaia region.
32 citations
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TL;DR: In this article, a 3D hydrodynamical radiative transfer model of the K1 V atmosphere was used to fit the new interferometric visibility measurements of α Cen B obtained with the VINCI instrument of the VLT Interferometer.
Abstract: For the nearby dwarf star α Cen B (K1 V), we present limb-darkening predictions from a 3D hydrodynamical radiative transfer model of its atmosphere. We first compared the results of this model to a standard Kurucz’s atmosphere. Then we used both predictions to fit the new interferometric visibility measurements of α Cen B obtained with the VINCI instrument of the VLT Interferometer. Part of these new visibility measurements were obtained in the second lobe of the visibility function, which is sensitive to stellar limb-darkening. The best agreement is found for the 3D atmosphere limb-darkening model and a limb-darkened angular diameter of θ3D = 6.000 ± 0.021 mas, corresponding to a linear radius of 0.863 ± 0.003R� (assuming π = 747.1 ± 1.2 mas). Our new linear radius agrees well with the asteroseismic value predicted by Thevenin et al. (2002, A&A, 392, L9). In view of future observations of this star with the VLTI/AMBER instrument, we also present limb-darkening predictions in the J, H ,a ndK bands.
6 citations
01 Jan 2006
TL;DR: In this article, the results of a spectroscopic analysis of bright stars in the Carina dSph galaxy were presented, in particular low-mass, old Red Giant, Asymptotic, and Horizontal Branch stars as well as intermediate-age stars of the Red Clump.
Abstract: We present the results of a spectroscopic analysis of bright stars in the Carina dSph galaxy We collected low-resolution FORS2@VLT spectra of ≈ 200 stars Our spectroscopic targets have been selected among the evolved Carina stars, in particular we selected low-mass, old Red Giant, Asymptotic, and Horizontal Branch stars, as well as intermediate-age stars of the Red Clump We present preliminary estimates concerning the radial velocities of old and intermediate-age populations
3 citations
01 Jan 2006
01 Dec 2006
TL;DR: In this article, the authors presented the first results concerning an extensive study of stellar populations of the Carina dSph galaxy, based on data collected with the multi-object spectrographs FORS2 and FLAMES, both available at VLT.
Abstract: Multi-object spectrographs available on 8-m class telescopes provide the unique opportunity to directly investigate the kinematical and chemical properties of significant samples of resolved stars in galaxies of the Local Group. We present here the first results concerning an extensive study of stellar populations of the Carina dSph galaxy, based on data collected with the multi-object spectrographs FORS2 and FLAMES, both available at VLT. Preliminary estimates concerning the radial velocity distributions of the different samples are presented.