Turck-Chièze, S.; Le Pennec, M.; Ducret, J. E.; Colgan, J.; Kilcrease, D. P.; Fontes, C. J.; Magee, N.; Gilleron, F.; Pain, J. C.
AA(CEA/IRFU/SAp, CE Saclay, F-91191 Gif sur Yvette, France Sylvaine.Turck-Chieze@cea.fr), AB(CEA/IRFU/SAp, CE Saclay, F-91191 Gif sur Yvette, France; CEA, DAM, DIF, F-91297 Arpajon, France), AC(CEA/IRFU/SAp, CE Saclay, F-91191 Gif sur Yvette, France; CELIA, UMR5107, 351 cours de la Libération, F-33405 Talence, France), AD(Theoretical Division, LANL, Los Alamos NM87545, USA 0000-0003-1045-3858), AE(Theoretical Division, LANL, Los Alamos NM87545, USA), AF(Comp. Phys. Division, LANL, Los Alamos NM 87545, USA), AG(Comp. Phys. Division, LANL, Los Alamos NM 87545, USA), AH(CEA, DAM, DIF, F-91297 Arpajon, France), AI(CEA, DAM, DIF, F-91297 Arpajon, France)
Seismic observations have led to doubts or ambiguities concerning the opacity calculations used in stellar physics. Here, we concentrate on the iron-group opacity peak, due to iron, nickel, and chromium, located around T = 200,000 K for densities from 10-8 to 10-4 g cm-3, which creates some convective layers in stellar radiative envelopes for masses between 3 and 18 Mo . These conditions were extensively studied in the 1980s. More recently, inconsistencies between OP and OPAL opacity calculations have complicated the interpretation of seismic observations as the iron-group opacity peak excites acoustic and gravity modes in SPB, beta Cephei, and sdB stars. We investigate the reliability of the theoretical opacity calculations using the modern opacity codes ATOMIC and SCO-RCG. We show their temperature and density dependence for conditions that are achievable in the laboratory and equivalent to astrophysical conditions. We also compare new theoretical opacity spectra with OP spectra and quantify how different approximations impact the Rosseland mean calculations. This detailed study estimates new ATOMIC and SCO-RCG Rosseland mean values for astrophysical conditions which we compare to OP values. Some puzzling questions are still under investigation for iron, but we find a strong increase in the Rosseland mean nickel opacity of a factor between 2 and 6 compared to OP. This appears to be due to the use of extrapolated atomic data for the Ni opacity within the OP calculations. A study on chromium is also shown.