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Testing stellar opacities with laser facilities
Le Pennec, Maëlle; TURCK-CHIEZE, Sylvaine; RIBEYRE, Xavier et al.
2015IAU General Assembly
 

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Abstract :
[en] Helio and asteroseismology (SoHo, KEPLER...) have produced observed acoustic oscillations of thousands of stars which characteristics are deeply linked to the transport of radiation inside the stars. However, the comparisons of seismic data with model predictions have led to significant discrepancies, which could be due to a bad knowledge of production and transport of energy.β-Cephei are pulsating stars, progenitor of supernovae and thus deeply linked to our understanding of stellar medium enrichment. Their study has shown some difficulty to predict the observed oscillation modes, which are directly linked to an opacity bump of the elements of the iron group (Cr, Fe, Ni) at log T=5.25 (κ-mechanism). We will show that several parameters of the stars (mass, age, metallicity) have a great influence on the amplitude of the bump, which impact their structure. We will then present the final results of an experiment conducted at LULI 2000 in 2011 on Cr, Fe and Ni compared to several opacity codes. We will show how to improve the opacity in the range of temperature around log T= 5.3.The Sun is a privilege place to test and validate physics. Since the recent update of the solar composition, there is a well established large discrepancy (Turck-Chièze et al. 2001) between solar models and seismic data, visible on the solar sound speed profile comparison.An explanation could be that the calculations of energy transport are not correctly taken into account.Unfortunately, there are very few experiments to validate these calculations (Bailey et al. 2014). That's why we are proposing an opacity experiment on a high-energy laser like LMJ, in the conditions of the radiative zone. We are exploiting in that purpose an approach called the Double Ablation Front to reach these high temperatures and densities at LTE and validate or not plasma effects and line widths. We will show the principle of this technique and the results of our simulations on several elements.In the mean time, we are also exploiting new opacity calculations thanks to the OPAS code (Blancard et al. 2012) at the conditions of the solar radiative zone. We will show the impact of these calculations on the solar model.
Disciplines :
Space science, astronomy & astrophysics
Physics
Author, co-author :
Le Pennec, Maëlle;  CEA
TURCK-CHIEZE, Sylvaine;  CEA
RIBEYRE, Xavier;  Centre Lasers Intenses & Applications CELIA UMR 5107, Université de Bordeaux
DUCRET, Jean-Eric;  CEA
Salmon, Sébastien ;  Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie
BLANCARD, Christophe;  CEA/DAM/DIF
COSSE, Philippe;  CEA/DAM/DIF
MONDET, Guillaume;  CEA/DAM/DIF
FAUSSURIER, Gérald;  CEA/DAM/DIF
CONSORTIUM, Opac;  CEA)
Language :
English
Title :
Testing stellar opacities with laser facilities
Publication date :
01 August 2015
Event name :
IAU General Assembly
Event organizer :
union Astronomique Internationale
Event place :
United States - Hawaii
Event date :
août 2015
Audience :
International
Available on ORBi :
since 25 January 2016

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