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

TL;DR

This paper compares various spectral opacity calculations for Fe and Ni relevant to stellar envelopes, highlighting differences due to configuration interaction effects and including new HULLAC-v9 calculations with full CI to improve accuracy.

Contribution

It introduces a detailed comparison of opacity codes, emphasizing the impact of configuration interaction and presenting new HULLAC-v9 calculations with full CI inclusion.

Findings

Significant differences found among opacity codes for Fe and Ni.

Full configuration interaction in HULLAC-v9 affects spectral opacity results.

Comparison with experimental data highlights the importance of CI effects.

Abstract

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.