Context. The chemical composition of the Sun is required in the context of various studies in astrophysics, among them in the calculation of standard solar models (SSMs) used to describe the evolution of the Sun from the pre-main-sequence to its present age. Aims. In this work, we provide a critical re-analysis of the solar chemical abundances and corresponding SSMs. Methods. For the photospheric values, we employed new high-quality solar observational data collected with the IAG facility, state-of-the art non-equilibrium modelling, new oscillator strengths, and different atmospheric models, including the MARCS model, along with averages based on Stagger and CO5BOLD 3D radiation-hydrodynamics simulations of stellar convection. We performed new calculations of oscillator strengths for transitions in O I and N I. For O I, which is a critical element with regard to the interior models, calculations were carried out using several independent methods. We investigated our results in comparison with the previous estimates. Results. We find an unprecedented agreement between the new estimates of transition probabilities, thus supporting our revised solar oxygen abundance value. We also provide new estimates of the noble gas Ne abundance. In addition, we discuss the consistency of our photospheric measurements with meteoritic values, taking into account the systematic and correlated errors. Finally, we provide revised chemical abundances, leading to a new value proposed for the solar photospheric present-day metallicity of Z/X = 0.0225, which we then employed in SSM calculations. We find that the puzzling mismatch between the helioseismic constraints on the solar interior structure and the model can be resolved thanks to this new chemical composition.

Aims. Our recent re-analysis of the solar photospheric spectra with non-local thermodynamic equilibrium (non-LTE) models resulted in higher metal abundances compared to previous works.When applying the new chemical abundances to Standard Solar Model calculations, the new composition resolves the long-standing discrepancies with independent constraints on the solar structure from helioseismology.Methods. Critical to the determination of chemical abundances is the accuracy of the atomic data, specially the f -values, used in the radiative transfer models. Here we describe in detail the calculations of f -values for neutral oxygen and nitrogen used in our non-LTE models.Results. Our calculations of f -values are based on a multi-method, multi-code approach and are the most detailed and extensive of its kind for the spectral lines of interest. We also report in this paper the details of extensive R-matrix calculation of photo-ionization cross sections for oxygen.Conclusions. Our calculation resulted in reliable f -values with well constrained uncertainties.We compare our results with previous theoretical and experimental determinations of atomic data.We also quantify the influence of adopted photo-ionisation cross-sections on the spectroscopic estimate of the solar O abundance, using the data from different sources. We confirm that the 3D non-LTE value presented by Bergemann et al. 2021 is robust and unaffected by the choice of photo-ionisation data, contrary to the recent claim made by Nahar.

Using two independent theoretical methods based on the pseudo-relativistic Hartree–Fock (HFR) and the fully relativistic Multiconfigurational Dirac–Hartree–Fock (MCDHF) approaches, we computed the radiative parameters (transition probabilities and oscillator strengths) corresponding to the spectrum of quadruply ionized lutetium (Lu V). The agreement observed between both sets of results allowed us to deduce the radiative rates for a large amount of transitions in order to calculate the contribution of this ion to the opacity of kilonovae in their early phases, i.e., for T = 25,000 K. The results obtained were compared to previous data computed for other quadruply ionized lanthanide atoms, namely La V, Ce V, Pr V, Nd V and Pm V, in order to highlight the main contributors to the opacity among these ions under kilonovae conditions where the Vth spectra are predominant.

In this study, the sensitivity of the opacities with respect to the atomic parameters is investigated in the case of weakly charged uranium ions. In order to do this, atomic data for U II and U III were calculated with the pseudo-relativistic Hartree-Fock method (HFR) and then, used to determine the expansion opacities for conditions characterizing the ejecta of kilonovae that follow neutron star mergers. In particular, we studied the sensitivity of the opacity with respect to the use of atomic data obtained considering several effects as the ionic core polarization and an adjustment procedure.

A new set of radiative parameters for spectral lines in La V–X ions is reported in the present paper. These data were determined through the use of a multi-platform approach involving three independent theoretical methods, i.e. the relativistic Hartree-Fock method including core-polarization corrections (HFR+CPOL), the multiconfiguration Dirac-Hartree-Fock (MCDHF) method, and the Particle-Hole Configuration Interaction (PH-CI) method implemented in the AMBiT program. Based on cross-comparisons between the results obtained with these three methods, and from comparisons with the few previously published experimental and theoretical data, the most complete and reliable set of wavelengths, transition probabilities and oscillator strengths was then used to determine the necessary opacities for the analysis of the spectra emitted in the early phases of kilonovae following neutron star mergers, i.e. for typical conditions corresponding to temperatures T > 20000 K, a density ρ = 10−10 g cm−3 and a time after the merger t = 0.1 day.