We describe the atomic database of the xstar spectral modeling code, summarizing the systematic upgrades carried out in the past twenty years to enable the modeling of K-lines from chemical elements with atomic number $Z\le 30$ and recent extensions to handle high-density plasmas. Such plasma environments are found, for instance, in the inner region of accretion disks round compact objects (neutron stars and black holes), which emit rich information about the system’s physical properties. Our intention is to offer a reliable modeling tool to take advantage of the outstanding spectral capabilities of the new generation of X-ray space telescopes (e.g., xrism and athena) to be launched in the coming years. Data curatorial aspects are discussed and an updated list of reference sources is compiled to improve the database provenance metadata. Two xstar spin-offs—the ISMabs absorption model and the uaDB database—are also described.

Context. The production of elements heavier than iron in the Universe still remains an unsolved mystery. About half of them are thought to be produced by the astrophysical r-process (rapid neutron-capture process), for which neutron star mergers (NSMs) are among the most promising production sites. In August 2017, gravitational waves generated by a NSM were detected for the first time by the LIGO detectors (event GW170817), and the observation of its electromagnetic counterpart, the kilonova (KN) AT2017gfo, suggested the presence of heavy elements in the KN ejecta. The luminosity and spectra of such KN emission depend significantly on the ejecta opacity. Atomic data and opacities for heavy elements are thus sorely needed to model and interpret KN light curves and spectra. Aims. The present work focuses on large-scale atomic data and opacity computations for all heavy elements with Z ≥ 20, with a special effort on lanthanides and actinides, for a grid of typical KN ejecta conditions (temperature, density, and time post-merger) between one day and one week after the merger (corresponding to the local thermodynamical equilibrium photosphere phase of the KN ejecta). Methods. In order to do so, we used the pseudo-relativistic Hartree–Fock (HFR) method as implemented in Cowan’s codes, in which the choice of the interaction configuration model is of crucial importance. Results. In this paper, HFR atomic data and opacities for all elements between Ca (Z = 20) and Lr (Z = 103) are presented, with a special focus on lanthanides and actinides. In particular, we found increased lanthanide opacities compared to previous works. Besides, we also discuss the contribution of every single element with Z ≥ 20 to the total KN ejecta opacity for a given NSM model, depending on their Planck mean opacities and elemental abundances. An important result is that lanthanides are found to not be the dominant sources of opacity, at least on average. The impact on KN light curves of considering such atomic-physics-based opacity data instead of typical crude approximation formulae is also evaluated. In addition, the importance of taking the ejecta composition into account directly in the expansion opacity determination (instead of estimating single-element opacities) is highlighted. A database containing all the relevant atomic data and opacity tables has also been created and published online along with this work.

In most accreting black-hole systems the copious X-rays commonly observed from the inner-most regions are accompanied by a reflection spectrum. The latter is the signature of energetic photons reprocessed by the optically thick material of an accretion disk. Given their abundance and fluorescence yield, the iron K-shell lines are the most prominent features in the X-ray reflected spectrum. Their line profiles can be grossly broadened and skewed by Doppler effects and gravitational redshift. Consequently, modeling the reflection spectrum provides one of the best methods to measure, among other physical quantities, the black-hole spin. At present the accuracy of the spin estimates is called into question because the data fits require very high iron abundances: typically several times the solar value. Concurrently no plausible physical explanation has been proffered for these black-hole systems to be so iron rich. The most likely explanation for the supersolar iron abundances is model shortfall at very high densities ($>10^{18}$ cm$^{-3}$) due to atomic data shortcomings in this regime. We review the current observational evidence for the iron supersolar abundance in many black-hole systems, and show the effects of high density in state-of-the-art reflection models. We also briefly discuss our current efforts to produce new atomic data for high-density plasmas, which are required to refine the photoionization models.

Aims. Neutron star (NS) mergers are thought to be a source of heavy trans-iron element production. The latter can be detected in the spectra of the ejected materials, from which bright electromagnetic radiation is emitted. This latter is due to the radioactive decay of the produced heavy r-process nuclei and is known as kilonova. Because of their complex atomic structures – characterized by configurations involving unfilled nd or nf subshells – the heavy elements of the kilonova ejecta often give rise to numerous absorption lines generating significant opacities. The determination of the latter, which are of paramount importance for the analysis of kilonova light curves, requires knowledge of the radiative parameters of the spectral lines belonging to the ions expected to be present in the kilonova ejecta. The aim of the present work is to provide new atomic opacity data for two representative 4d elements, niobium (Nb) and silver (Ag), in their first four charge states, namely for Nb I–IV and Ag I–IV. Methods. Large-scale calculations based on the pseudo-relativistic Hartree-Fock (HFR) method were performed to obtain the atomic structure and radiative parameters while the expansion formalism was used to estimate the opacities. Results. Wavelengths and oscillator strengths were computed for several million spectral lines in Nb I–IV and Ag I–IV ions. The reliability of these parameters was estimated by comparison with the few previously published experimental and theoretical results. The newly obtained atomic data were then used to calculate expansion opacities for typical kilonova conditions expected one day after NS merger, a density of ρ = 10⁻¹³ g cm⁻³, and temperatures ranging from T = 5000 K to T =15 000 K.