Open M-shell Fe and Ni LTE opacity calculations with the code HULLAC-v9

It has been shown that a careful evaluation of the δn = 0 M-shell in Fe and Ni is necessary to obtain consistent stellar model predictions. At astrophysical conditions of T_e = 15.3 eV, n_e = 10¹³ 10²²cm^-3, the δn = 0 M-shell and absorption transitions among M to N and M to O shells arising from the ions Fe III through Fe XV, have been computed in the using detailed level accounting (DLA) with configuration interaction (CI), assuming LTE. The importance of extensive CI computations is shown by systematically increasing the size of the CI basis until convergence. Iron opacity results, including M-shell and M to upper shells transitions up to δn = 2, are presented and the influence of the number of atomic levels is discussed. These very large computations -e.g. ~7.3 × 10⁵ levels or ~5700 relativistic configurations in Fe VII- were performed using the flexibility and the efficiency of an updated version of the HULLAC-v9.5 code. Results for Ni are also reported. HULLAC-v9.5 results are compared with those of other codes and databases, STA, SCO-RCG and OPCD3.3.