Iron opacity predictions under solar interior conditions

Whittaker, D. S.; Tallents, G. J.

doi:10.1111/j.1365-2966.2009.15523.x

Cited by 11 publications

(7 citation statements)

References 54 publications

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“…The iron case is probably also slightly underestimated. The origins of the discrepancies have been looked for using HULLAC detailed computations (see Gilles et al these proceedings): some transitions that play a role in the mean Rosseland values have not been taken into account in OP tables, moreover the interaction of configuration plays a non negligible role and seems to be absent from OPAL calculations, see the comparison with the Da Silva experiment by Whittaker & Tallents (2009) and Figure 2 of Gilles et al (2012). So in order to get more accuracy on the iron peak, one needs to improve the whole calculations of the different elements that participate to it.…”

Section: First Lessons From Opacity Calculation Comparisonsmentioning

confidence: 99%

Seismology of Sun and stars and related opacity laboratory measurements

Turck‐Chièze

2012

EAS Publications Series

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Abstract. CNES, ESA and NASA have invested in helioseismic and asteroseismic disciplines for 2 decades with SoHO (1995SoHO ( -2015, COROT (2006COROT ( -2013, KEPLER (2009KEPLER ( -2014, PICARD (2010PICARD ( -2013 and SDO (2010SDO ( -2015. These missions focus on the stellar internal dynamics and their influence of neighboring planets. Progress along this path requires that the microscopic physics is well under control, but several seismic probes indicate some discrepancies which justify new investigations of the energy transport in radiative zones of the Sun and massive stars, despite strong efforts dedicated to reaction rates, screening, equation of state and opacity coefficients between 1990 and 2000. We describe here how the OPAC consortium tackles the complex problem of photon absorption by matter both theoretically and experimentally, by using high energy laser facilities. These studies might be also useful for other disciplines like fusion for energy and X-ray spectroscopy astronomy.

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Section: First Lessons From Opacity Calculation Comparisonsmentioning

confidence: 99%

Seismology of Sun and stars and related opacity laboratory measurements

Turck‐Chièze

2012

EAS Publications Series

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“…For the importance of electron collision equilibrium, many discussions have taken place about the calculations of the parameters in electron collision equilibrium, such as the CHIANTI database, which is a primary source of atomic data employed by astrophysicists and plasma * E-mail: hejian405@163.com; Fax: +86-6562-6263 physicists for the evaluation of the temperature and the electron density diagnostic line ratios and other modeling applications [11,12]. The O III ion is an important ion for studying the properties of the solar plasma, so in this paper, by taking the solar O III ion as an example, we will discuss temperature diagnostics by using the collision excitation model.…”

Section: Introductionmentioning

confidence: 99%

Solar plasma diagnostic for O III spectral lines by using the collision excitation model

Zhang

2015

Journal of the Korean Physical Society

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In this paper, using the collisions between ions and free electrons, we discuss the conditions for electron collision equilibrium. Using collision excitation and de-excitation, we discuss a method for a solar temperature diagnostic for three-level ions. Taking the O III ion as an example, for the intensity ratio of the (2-1) transition to the (3-2) transition, we calculate the temperature when the intensity ratio varies from 10 to 200, and we obtain some useful conclusions. This discussion is important for solar plasma diagnostic under the conditions of electron collision equilibrium.

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“…The left panel of Figure 4, coming from [27], shows the transmission spectrum of iron obtained with OPAL and OP, and also with an experiment done by [28] twenty years ago. In this figure, one sees clearly the effect of CI between OPAL and OP (displacement of the spectrum toward higher energy).…”

Section: Comparison With Experimental Spectramentioning

confidence: 99%

“…Comparison between experimental opacity spectrum of [28] and OP and OPAL, extracted from [27]. Right: comparison with different options of the HULLAC calculations [15].…”

Section: Figure 4 Leftmentioning

confidence: 99%

News from the opacity consortium OPAC

Turck‐Chièze

Gilles

2013

EPJ Web of Conferences

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Abstract. The international OPAC consortium (see list below) was formed three years ago. It is composed of astrophysicists, plasma physicists and experimentalists from different laboratories b . This consortium examines specific opacity calculations used in stellar physics. They contribute to solve the problems suggested by the astrophysical community in performing new calculations and new experiments with laser installation. We show here the specific example of the iron opacity peak that plays an important role in the envelope of intermediate-mass and massive stars and we present our first conclusions on iron and nickel. OPEN PROBLEMS COMING FROM SEISMIC OBSERVATIONSThe stellar community hopes to progress on the internal dynamics of stars thanks to the space-borne seismic missions SoHO, CoRoT and Kepler. But good identification and interpretation of acoustic frequencies are based on a proper microscopic physics. Along the last decade, some questions on energy transfer, linked to plasma opacities, have arisen and two cases have retained our attention. 1. The extraction of the solar internal sound speed and density has revealed clear discrepancies with the Standard Solar Model predictions [1][2][3]. These discrepancies are not explained by the transport of momentum by rotation during the main sequence evolution [4]. So the energy balance and (or) energy transfer stay clearly under suspicion. In parallel, the recent OPAS calculations [5] have revealed large differences in individual element spectra with previous calculations and in particular with OP [6,7]. OPAS calculations also show some compensation effects between low Z nuclei and the iron group contributions in the Rosseland mean opacity values. All these facts encourage further works and experimental verifications. 2. The second case concerns massive stars. SPB and Cephei stars are interesting pulsators that might put important constraints on rotation and magnetic fields, two key actors for massive stars. Presently, the 40 stars observed by Kepler show acoustic and gravity modes probably up to = 20 (deformed stars) that are difficult to identify [8]. The first difficulty comes from the iron group opacities, which drive their pulsations. The observed modes do not agree with the stability of modes deduced from the OP or OPAL tables [9], which suggests that those opacities are underestimated [10,11]. Up to now, our effort is dedicated to the second case. The first analysis of the OPAC consortium confirms an underestimate of these opacities through comparison with more recent opacity calculations based on old and new measurements [12][13][14][15]. We shall here present our first conclusions and new orientations for the coming years.

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Iron opacity predictions under solar interior conditions

Cited by 11 publications

References 54 publications

Seismology of Sun and stars and related opacity laboratory measurements

Seismology of Sun and stars and related opacity laboratory measurements

Solar plasma diagnostic for O III spectral lines by using the collision excitation model

News from the opacity consortium OPAC

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