相关论文: Statistical equilibrium of silicon in the solar at…

We examine the accuracy of a common FIP effect diagnostic, the ratio of Ne VI to Mg VI lines in the solar transition region. Since the two ions have quite similar contribution functions near their maxima in equilibrium, the ratio of these…

An initial theoretical attempt to explain the observed decrease of the polytropic/adiabatic index $\gamma$ in the solar corona has been accomplished. The chemical reactions of the ionization-recombination processes in local thermodynamic…

The possibility of unaccounted for opacity sources in the UV for late-type stars has often been invoked to explain discrepancies between predicted and observed flux distributions and spectral line strengths. Such missing UV-opacity could…

The chemical composition of the Sun is among the most important quantities in astrophysics. Solar abundances are needed for modelling stellar atmospheres, stellar structure and evolution, population synthesis, and galaxies as a whole. The…

We have developed a model atom for Cu with which we perform statistical equilibrium computations that allow us to compute the line formation of Cu I lines in stellar atmospheres without assuming Local Thermodynamic Equilibrium (LTE). We…

Context. The solar irradiance is known to change on time scales of minutes to decades, and it is suspected that its substantial fluctua- tions are partially responsible for climate variations. Aims. We are developing a solar atmosphere code…

We study the formation of B I lines in a grid of cool stellar model atmospheres without the assumption of local thermodynamic equilibrium (LTE). The non-LTE modelling includes the effect of other lines blending with the B I resonance lines.…

CONTEXT: Spectral-line asymmetries and wavelength shifts are signatures of hydrodynamics in solar and stellar atmospheres. Theory may precisely predict idealized lines, but observed spectra are limited by blends, too few suitable lines,…

Medium resolution J-band spectroscopy of individual red supergiant stars is a promising tool to investigate the chemical composition of the young stellar population in star forming galaxies. As a continuation of recent work on iron and…

An extensive beryllium abundance analysis was conducted for 118 solar analogs (along with 87 FGK standard stars) by applying the spectrum synthesis technique to the near-UV region comprising the Be II line at 3131.066 A, in an attempt to…

We performed the non-local thermodynamic equilibrium (non-LTE) calculations for Ti I-II with the updated model atom that includes quantum-mechanical rate coefficients for inelastic collisions with hydrogen atoms. We have calculated for the…

Synthetic stellar spectra are extensively used for many different applications in astronomy, from stellar studies (such as in the determination of atmospheric parameters of observed stellar spectra), to extragalactic studies (e.g. as one of…

A new model atom of Sc II was constructed using the most up-to-date atomic data. For the testing purpose, the non-local thermodynamic equilibrium (non-LTE) calculations were carried out for three stars with reliably determined atmospheric…

Neutral Fe lines in metal-poor stars yield conflicting abundances depending on whether and how deviations from local thermodynamic equilibrium (LTE) are considered. We have collected new high resolution and high signal-to-noise ultraviolet…

We present accurate methods of abundance determination based on the non-local thermodynamic equilibrium (NLTE) line formation for carbon, oxygen, calcium, titanium, and iron in the atmospheres of BAF-type stars. For C I-II, O I, Ca I-II,…

A non-LTE analysis of C I lines at 1.068-1.069 micron was carried out for selected 46 halo/disk stars covering a wide metallicity range (-3.7 <[Fe/H]< +0.3), based on the spectral data collected with IRCS+AO188 of the Subaru Telescope, in…

The aim of this work is to obtain precise atmospheric parameters and chemical abundances automatically for solar twins and analogs to find signatures of exoplanets, as well as to assess how peculiar the Sun is compared to these stars and to…

Luminosity, which is the total amount of radiant energy emitted by an object, is one of the most critical quantities in astrophysics for characterizing stars. Equally important is the temporal evolution of a star's luminosity because of its…

We present a detailed spectroscopic analysis of nitrogen abundances in 91 solar-type stars, 66 with and 25 without known planetary mass companions. All comparison sample stars and 28 planet hosts were analysed by spectral synthesis of the…

For the first time, we establish a gas phase abundance pattern calibration for quiescent galaxies using optical emission lines. Quiescent galaxies have warm ionized gas showing line ratios similar to low-ionization nuclear emission line…