SOLAR MIXTURE OPACITY CALCULATIONS USING DETAILED CONFIGURATION AND LEVEL ACCOUNTING TREATMENTS

International audienc

First New Solar Models With Opas Opacity Tables

Stellar seismology appears more and more as a powerful tool for a better determination of the fundamental properties of solar-type stars. However, the particular case of the Sun is still challenging. For about a decade now, the helioseismic sound-speed determination has continued to disagree with the standard solar model (SSM) prediction, questioning the reliability of this model. One of the sources of uncertainty could be in the treatment of the transport of radiation from the solar core to the surface. In this Letter, we use the new OPAS opacity tables, recently available for solar modeling, to address this issue. We discuss first the peculiarities of these tables, then we quantify their impact on the solar sound-speed and density profiles using the reduced OPAS tables taken on the grids of the OPAL ones. We use the two evolution codes, Modules for Experiments in Stellar Astrophysics and Code Liégeois d'Evolution Stellaire, that led to similar conclusions in the solar radiative zone. In comparison to commonly used OPAL opacity tables, the new solar models are computed for the most recent photospheric composition with OPAS tables and present improvements to the location of the base of the convective zone and to the description of the solar radiative zone in comparison to the helioseismic observations, even if the differences in the Rosseland mean opacity do not exceed 6%. We finally carry out a comparison to a solar model computed with the OP opacity tables

Photoionization cross sections of iron isonuclear sequence ions: Fe2+ to Fe6+

International audienceWe have measured the absolute photoionization cross sections of Fe2+ to Fe6+ ions in the photon energy range covering the first ionization threshold up to 160 eV. Particular interest is emphasized on the region of the 3p-->3d excitations. The experimental data are compared to the results of calculations we have performed using a spectral opacity code, as well as to available R -matrix and one-electron calculations. It is shown that often the theoretical results tend to overestimate the intensity of the 3p-->3d photoexcitations. An anomalously low value of the integrated oscillator strength is measured for Fe2+ ion

Recent developments on photoionization measurements on mutiply-charged ions at ASTRID and SOLEIL

International audienceThe merged-beams technique, which consists in merging an ion beam with a synchrotron radiation beam, allows to determine absolute photoionization cross sections on ionic species. In this poster, we will discuss recent results we have obtained on ions of the iron isonuclear sequence in the photon energy range covering the first ionization threshold up to 160 eV. Future developments of the experiments at SOLEIL will be also presented

Lettres adressées à la maréchale de Cossé.

Cossé, Nicole Le Roy, Comtesse de. Lettre(s) reçue(s)Cossé-Brissac, Comte Philippe de. Manuscrit(s) provenant de luiContient : Baudry, Chanoine J.. Note(s) ; Cossé-Brissac, Comte Philippe de. Lettre(s) ; Pouët, Abbé François, vicaire général de Rennes. Note(s) sur l'Affaire Turmel ; Aspremont, Adrien d', gouverneur de Bayonne. Lettre(s) ; Cossé, Artus, Comte de, maréchal de France. Lettre(s) ; Cossé, Jeanne de, dame de Gonnor. Lettre(s) ; Lenoncourt, M. de. Lettre(s) ; Mongommery, G.E.. Lettre(s) ; Turgot, Charles. Lettre(s) ; Charost, Alexis-Armand, cardinal. Lettre(s) ; Dasse, Sœur. Lettre(s) ; Pouët, Abbé François, vicaire général de Rennes. Lettre(s) reçue(s) ; Lejay, Abbé Paul, professeur de Faculté catholique. Lettre(s) reçue(s) ; Sartiaux, Félix. Lettre(s)Numérisation effectuée à partir d'un document original : NAF 13294.On y trouve notamment : cinq lettres d'Artus de Cossé, dont deux entièrement autographe (5-10), et une lettre de Jeanne de Cossé, fille du précédent (11). Ces documents proviennent du chartrier d'Azay-le-Rideau

Comparison of Fe and Ni opacity calculations for a better understanding of pulsating stellar envelopes

International audienceOpacity is an important ingredient of the evolution of stars. The calculation of opacity coefficients is complicated by the fact that the plasma contains partially ionized heavy ions that contribute to opacity dominated by H and He. Up to now, the astrophysical community has greatly benefited from the work of the contributions of Los Alamos [1], Livermore [2] and the Opacity Project (OP) [3]. However unexplained differences of up to 50% in the radiative forces and Rosseland mean values for Fe have been noticed for conditions corresponding to stellar envelopes. Such uncertainty has a real impact on the understanding of pulsating stellar envelopes, on the excitation of modes, and on the identification of the mode frequencies. Temperature and density conditions equivalent to those found in stars can now be produced in laboratory experiments for various atomic species. Recently the photo-absorption spectra of nickel and iron plasmas have been measured during the LULI 2010 campaign, for temperatures between 15 and 40 eV and densities of ˜3 mg/cm3. A large theoretical collaboration, the "OPAC", has been formed to prepare these experiments. We present here the set of opacity calculations performed by eight different groups for conditions relevant to the LULI 2010 experiment and to astrophysical stellar envelope conditions

La coopération universitaire entre la France et le Québec

Le vingtième anniversaire de l’Entente franco-québécoise de 1965 a fourni l’occasion au Centre de Coopération Universitaire d’organiser un colloque consacré, en deux phases, à un premier bilan et aux perspectives de cette coopération. Le présent volume, grâce à diverses contributions dont la spontanéité a été, dans le mesure du possible, respectée, permet de se faire une meilleure image de la coopération universitaire franco-québécoise. Le pessimisme qui ressort du rappel historique, comme de certaines interventions, subsiste car la situation reste très incertaine, mais il doit être considérablement nuancé. Les partenaires de la coopération ont su s’adapter à une conjoncture difficile, ils continuent à œuvrer, par tous les moyens, à la poursuite et au développement d’une coopération exemplaire pour les deux pays. Puissent les conclusions de ce colloque permettre une meilleure perception des problèmes qui subsistent, et servir, peut-être, d’ébauches de solution. Plus généralement ce colloque, bien que consacré à la seule coopération franco-québécoise, pose des questions, présente des situations, envisage des voies d’avenir qui peuvent servir d’exemples pour tout autre cas de coopération universitaire internationale. Au-delà de leur but immédiat, les responsables du présent volume seraient très satisfaits si leurs réflexions pouvaient, ainsi, être plus largement utiles, fournissant une nouvelle preuve des bienfaits de la coopération universitaire

Theoretical and experimental activities on opacities for a good interpretation of seismic stellar probes

International audienceOpacity calculations are basic ingredients of stellar modelling. They play a crucial role in the interpretation of acoustic modes detected by SoHO, COROT and KEPLER. In this review we present our activities on both theoretical and experimental sides. We show new calculations of opacity spectra and comparisons between eight groups who produce opacity spectra calculations in the domain where experiments are scheduled. Real differences are noticed with real astrophysical consequences when one extends helioseismology to cluster studies of different compositions. Two cases are considered presently: (1) the solar radiative zone and (2) the beta Cephei envelops. We describe how our experiments are performed and new preliminary results on nickel obtained in the campaign 2010 at LULI 2000 at Polytechnique