Confronting atomic data with Fe L-shell spectra of stellar coronae

It is common to suggest the uncertainties in the atomic data for explaining difficulties that arise in interpreting astrophysical x-ray spectra. The atomic data for the Fe L-shell ions have, over the years, been considered particularly suspect. In this paper, we confront Fe-L spectra calculated using the HULLAC atomic code assuming coronal conditions with recent observations of the stellar coronae of Capella and HR 1099, obtained with the high-resolution grating spectrometers on board Chandra and XMM-Newton. We find very good agreement, which indicates that Fe-L transition rates calculated with state-of-the-art codes, can generally be trusted in the analysis of x-ray spectra.