Related papers: NLTE for APOGEE: Simultaneous Multi-Element NLTE R…

We calculate a grid of spherically symmetric OB stellar atmospheres at low metallicities, including both non-local thermodynamic equilibrium (NLTE) and metal line blanketing effects. This is done to assess the uncertainties in helium…

We investigate the ability of both LTE and Non-LTE models to fit the near UV band absolute flux distribution and individual spectral line profiles of three standard stars for which high quality spectrophotometry and high resolution…

We present a technique to treat systems with very many levels, like molecules, in non-LTE. This method is based on a superlevel formalism coupled with rate operator splitting. Superlevels consist of many individual levels that are assumed…

Abundances of five elements, Na, Mg, Al, Si, and Sr, are investigated for 44 very metal-poor stars (-4.0 < [Fe/H] < -1.5) in the Galactic halo system based on an Local Thermodinamic Equilibrium (LTE) analysis of high-resolution…

We performed non-LTE calculations for O I with the plane-parallel model atmospheres for a set of stellar parameters corresponding to A-K type stars. The model atom of Przybilla et al. (2000) was updated using the best theoretical and…

Some studies of stars' multi-element abundance distributions suggest at least 5-7 significant dimensions, but others show that many elemental abundances can be predicted to high accuracy from [Fe/H] and [Mg/Fe] (or [Fe/H] and age) alone. We…

Whenever observations are compared to theories, an estimate of the uncertainties associated with the observations is vital if the comparison is to be meaningful. However, many determinations of temperatures, densities and abundances in…

Massive sets of stellar spectroscopic observations are rapidly becoming available and these can be used to determine the chemical composition and evolution of the Galaxy with unprecedented precision. One of the major challenges in this…

Non-LTE calculations for Mg I in red supergiant stellar atmospheres are presented to investigate the importance of non-LTE for the formation of Mg I lines in the NIR J-band. Recent work using medium resolution spectroscopy of atomic lines…

Extensive statistical-equilibrium calculations on neutral sulfur and zinc were carried out, in order to investigate how the non-LTE effect plays a role in the determination of S and Zn abundances in F, G, and K stars. Having checked on the…

We describe our implementation of an extremely detailed model atom of singly ionized iron for NLTE computations in static and moving astrophysical plasmas. Our model atom includes 617 levels, 13675 primary permitted transitions and up to…

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…

(abridged) We present deep spectroscopy of a large sample of low-metallicity emission-line galaxies. The main goal of this study is to derive element abundances in these low-metallicity galaxies. We analyze 121 VLT spectra of HII regions in…

Differential abundances of C, O, Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Y, and Zr were determined from high signal-to-noise VLT/UVES spectra for 25 turnoff stars with -2.4 < [Fe/H] < -1.3. Effective temperatures were obtained from…

The chemical compositions of stars encode the history of the universe and are thus fundamental for advancing our knowledge of astrophysics and cosmology. However, measurements of elemental abundances ratios, and our interpretations of them,…

Red supergiants with their enormous brightness at J-band are ideal probes of cosmic chemical composition. It is therefore crucial to have realistic models of radiative transfer in their atmospheres, which will permit determination of…

The standard nonlocal thermodynamic equilibrium (non-LTE) multi-level radiative transfer problem only takes into account the deviation of the radiation field and atomic populations from their equilibrium distribution. We aim to show how to…

Magnesium is one of the important elements in stellar physics as an electron donor and in Galactic Archaeology as a discriminator of different stellar populations. However, previous studies of Mg I and Mg II lines in metal-poor benchmark…

Stellar parameters and abundances provide crucial insights into stellar and Galactic evolution studies. In this work, we developed a convolutional neural network (CNN) to estimate stellar parameters: effective temperature…

Non-local thermodynamic equilibrium (NLTE) effects in diagnostically important solar Fe I lines are important due to the strong sensitivity of Fe I to ionizing UV radiation, which may lead to a considerable under-population of the Fe I…