Related papers: Radiative transfer in cylindrical threads with inc…
The possibility of significant systematic errors due to the use of 1D homogeneous atmospheres in lithium-abundance determinations of cool stars motivates a study of non-local-thermodynamic-equilibrium (NLTE) effects on Li I line formation…
Since the mass of the electron is very small relative to atomic masses, Thomson scattering of low-energy photons ($h\nu \ll m_ec^2$) produces thermal Doppler frequency shifts that are much larger than atomic Doppler widths. A method is…
The nebular phase of a supernova (SN) occurs several months to years after the explosion, with asymmetries created by the explosion encoded into the line profiles of the emission lines. To make accurate predictions for these line profiles,…
We investigate statistical equilibrium of neutral and singly-ionized strontium in late-type stellar atmospheres. Particular attention is given to the completeness of the model atom, which includes new energy levels, transition…
Context. Three-dimensional non-local thermodynamical equilibrium (NLTE) radiative transfer calculations are a fundamental tool for a detailed spectral analysis in stellar atmospheres, but require vast amounts of computer power. This…
In the first three papers of this series, we investigated the formation of photospheric neutral iron lines in different atmospheres ranging from idealised flux tube models to complex three-dimensional magnetohydrodynamic (3D MHD)…
Physically realistic models of stellar spectra are needed in a variety of astronomical studies, from the analysis of fundamental stellar parameters, to studies of exoplanets and stellar populations in galaxies. Here we present a new version…
We test our knowledge of the atomic opacity in the solar UV spectrum. Using the atomic data compiled in Paper I from modern, publicly available, databases, we perform calculations that are confronted with space-based observations of the…
The hydrogen and water molecules respond very differently to the collisional-radiative processes taking place in planetary atmospheres. Naturally, the question arises whether H2O-rich atmospheres are more (or less) resilient to long-term…
Although the spectral lines of hydrogen contain valuable information on the physical properties of a variety of astrophysical plasmas, including the upper solar chromosphere, relatively little is known about their scattering polarization…
The ionization of hydrogen in the solar chromosphere and transition region does not obey LTE or instantaneous statistical equilibrium because the timescale is long compared with important hydrodynamical timescales, especially of…
We describe our method to construct line blanketed NLTE model atmospheres for hot stars. We employ the Accelerated Lambda Iteration and use statistical methods to deal with metal line blanketing.
We present a new detailed model of the He I collisional-recombination spectrum based on the most up-to-date atomic data. The model accounts for radiative transfer effects and the influence of a non-zero optical depth in He I lines arising…
Scattering line polarization and the Hanle effect are among the most important mechanisms for diagnostics of the solar and stellar atmospheres. The fact that real stellar atmospheres are horizontally inhomogeneous makes the spectral…
Context. Departures from local thermodynamic equilibrium (LTE) distort the calcium abundance derived from stellar spectra in various ways, depending on the lines used and the stellar atmospheric parameters. The collection of atomic data…
Using 1D NLTE radiative hydrodynamics we model the influence of the particle beams on the Halpha line profile treating the beam propagation and the atmosphere evolution self-consistently. We focus on the influence of the non-thermal…
Spectra of late-type stars are usually analyzed with static model atmospheres in local thermodynamic equilibrium (LTE) and a homogeneous plane-parallel or spherically symmetric geometry. The energy balance requires particular attention, as…
In the aim of determining accurate iron abundances in stars, this work is meant to empirically calibrate H-collision cross-sections with iron, where no quantum mechanical calculations have been published yet. Thus, a new iron model atom has…
We investigate the formation of neutral and singly ionized scandium lines in the solar photospheres. The research is aimed derive solar $\log gf\epsilon_{\odot}$(Sc) values for scandium lines, which will later be used in differential…
Line-formation calculations in the Rayleigh-Jeans tail of the spectral energy distribution are complicated by an amplification of non-LTE effects. For hot stars this can make quantitative modelling of spectral lines in the near-IR…