Updated opacities from the opacity project

Using the code autostructure, extensive calculations of inner-shell atomic data have been made for the chemical elements He, C, N, O, Ne, Na, Mg, Al, Si, S, Ar, Ca, Cr, Mn, Fe and Ni. The results are used to obtain updated opacities from the Opacity Project (OP). A number of other improvements on earlier work have also been included. Rosseland-mean opacities from the OP are compared with those from OPAL. Differences of 5-10 per cent occur. The OP gives the 'Z-bump', at log(T) 5.2, to be shifted to slightly higher temperatures. The opacities from the OP, as functions of temperature and density, are smoother than those from OPAL. The accuracy of the integrations used to obtain mean opacities can depend on the frequency mesh used. Tests involving variation of the numbers of frequency points show that for typical chemical mixtures the OP integrations are numerically correct to within 0.1 per cent. The accuracy of the interpolations used to obtain mean opacities for any required values of temperature and density depends on the temperature-density meshes used. Extensive tests show that, for all cases of practical interest, the OP interpolations give results correct to better than 1 per cent. Prior to a number of recent investigations which have indicated a need for downward revisions in the solar abundances of oxygen and other elements, there was good agreement between properties of the Sun deduced from helioseismology and from stellar evolution models calculated using OPAL opacities. The revisions destroy that agreement. In a recent paper, Bahcall et al. argue that the agreement would be restored if opacities for the regions of the Sun with 2 × 106T 5 × 106 K (0.7-0.4 R) were larger than those given by OPAL by about 10 per cent. In the region concerned, the present results from the OP do not differ from those of OPAL by more than 2.5 per cent

A quantitative comparison of opacities calculated using the distorted-wave and R-matirx methods

peer reviewe

Iron and Nickel spectral opacity calculations in conditions relevant for pulsating stellar envelopes and experiments

Seismology of stars is strongly developing. To address this question we have formed an international collaboration OPAC to perform specific experimental measurements, compare opacity calculations and improve the opacity calculations in the stellar codes [1]. We consider the following opacity codes: SCO, CASSANDRA, STA, OPAS, LEDCOP, OP, SCO-RCG. Their comparison has shown large differences for Fe and Ni in equivalent conditions of envelopes of type II supernova precursors, temperatures between 15 and 40 eV and densities of a few mg/cm3 [2, 3, 4]. LEDCOP, OPAS, SCO-RCG structure codes and STA give similar results and differ from OP ones for the lower temperatures and for spectral interval values [3]. In this work we discuss the role of Configuration Interaction (CI) and the influence of the number of used configurations. We present and include in the opacity code comparisons new HULLAC-v9 calculations [5, 6] that include full CI. To illustrate the importance of this effect we compare different CI approximations (modes) available in HULLAC-v9 [7]. These results are compared to previous predictions and to experimental data. Differences with OP results are discussed.Comment: 4 pages, 3 figures, conference Inertial Fusion Sciences and Applications, Bordeaux, 12th to 16th September 2011; EPJ web of Conferences 201

OSCILLATOR STRENGTHS FOR ALLOWED TRANSITIONS IN NEUTRAL OXYGEN : AN ASSESSMENT OF THE OPACITY PROJECT DATA ACCURACY

Plusieurs séries de forces d'oscillateur pour des transitions permises dans l'oxygène neutre, calculées dans le cadre du projet international Opacity, sont présentées et comparées à des données tant expérimentales que théoriques obtenues par d'autres auteurs. On montre que les présents résultats sont d'une haute précision.Several series of oscillator strengths for allowed transitions in neutral oxygen, calculated in the framework of the international Opacity Project, are presented and compared with both experimental and theoretical data obtained by other authors. It is shown that the present results are of high accuracy

PROBABILITIES FOR FORBIDDEN TRANSITIONS IN ATOMS AND IONS : 1968-1989. A BIBLIOGRAPHY

On donne une liste de plus de 240 références concernant les probabilités des transitions interdites dans les atomes et ions. La période couverte va de 1968 à 1989. Cette bibliographie est indexée en fonction des espèces traitées dans chacune des publications retenues.A list is given of over 240 references concerning probabilities for forbidden transitions in atoms and ions. The period covered goes from 1968 to 1989. This bibliography is indexed according to the species treated in each of the selected publications

OPACITY PROJECT : RADIATIVE LIFETIMES FOR IONS IN THE Mg ISOELECTRONIC SEQUENCE

L'utilité de l'ensemble des forces d'oscillateur du Projet Opacity en vue du calcul de temps de vie radiatifs est examinée dans le cas des ions de la séquence isoélectronique de Mg. On discute brièvement les effets intéressants concernant les tendances spectroscopiques et isoélectroniques. L'accord entre les présents temps de vie et ceux calculés précédemment à l'aide des meilleures méthodes disponibles est très bon, mais la comparaison avec un vaste ensemble de données experimentales est moins satisfaisante. Nous concluons que le présent ensemble de données est d'une précision statistique plus grande que les valeurs mesurées.The usability of the Opacity Project f-value dataset for the calculation of radiative lifetimes is examined in connection with ions in the Mg isoelectronic sequence. Interesting effects regarding spectroscopic and isoelectronic trends are briefly discussed. The agreement of the present lifetimes with those previously calculated by state-of the-art methods is very good, but the comparison with ample experimental data is patchy. We conclude that the present dataset is of higher statistical accuracy than the measured values

RECENT RADIATIVE AND COLLISIONAL ATOMIC DATA OF ASTROPHYSICAL INTEREST

A l'aide de programmes d'ordinateur sophistiqués et de modèles physiques élaborés, des données atomiques radiatives et collisionnelles précises d'intérêt astrophysique ont été ou sont en train d'être calculées. Les cas traités comprennent les transitions radiatives entre états liés dans les configurations 2p4 et 2s2p5 de nombreux ions de la séquence isoélectronique de l'oxygène, la photoionisation de l'état fondamental du fer neutre, l'excitation par impact électronique des transitions interdites de structure fine dans la configuration fondamentale 3p3 de C2 III, Ar IV et K V, et la production en masse de données radiatives pour les ions des séquences isoélectroniques de l'oxygène et du fluor, en tant que contribution au projet international Opacity.Using sophisticated computer programs and elaborate physical models, accurate radiative and collisional atomic data of astrophysical interest have been or are being calculated. The cases treated include radiative transitions between bound states in the 2p4 and 2s2p5 configurations of many ions in the oxygen isoelectronic sequence, the photoionisation of the ground state of neutral iron, the electron impact excitation of the fine-structure forbidden transitions within the 3p3 ground configuration of C2 III, Ar IV and K V, and the mass-production of radiative data for ions in the oxygen and fluorine isoelectronic sequences, as part of the international Opacity Project