相关论文: Non-LTE line-formation for hydrogen revisited
Non-LTE line formation for Pr II and Pr III is considered through a range of effective temperatures between 7250 K and 9500 K. A comprehensive model atom for Pr II/III is based on the measured and the predicted energy levels, in total, 6708…
We construct a comprehensive model atom for TiI-II using more than 3600 measured and predicted energy levels of TiI and 1800 energy levels of TiII, and quantum mechanical photoionisation cross-sections. Non-local thermodynamical equilibrium…
Context. The pursuit of more realistic spectroscopic modelling and consistent abundances has led us to begin a new series of papers designed to improve current solar and stellar abundances of various atomic species. To achieve this, we have…
The abundances of carbon, oxygen, and iron in late-type stars are important parameters in exoplanetary and stellar physics, as well as key tracers of stellar populations and Galactic chemical evolution. We carried out three-dimensional (3D)…
Convective motions in solar-type stellar atmospheres induce Doppler shifts that affect the strengths and shapes of spectral absorption lines and create slightly asymmetric line profiles. 1D LTE studies of elemental abundances are not able…
We discuss results of an exploratory non-LTE analysis of two metal-rich A-type supergiants in M31. Using comprehensive model atoms we derive accurate atmospheric parameters from multiple indicators and show that non-LTE effects on the…
Spectral lines of helium are commonly observed on the Sun. These observations contain important informations about physical conditions and He/H abundance variations within solar outer structures. The modeling of chromospheric and coronal…
Giving new insight for line broadening theory for atoms with more structure than hydrogen in most stars. Using symbolic software to build precise wave functions corrected for ds;dp quantum defects. The profiles obtained with that approach,…
The formation of the resonance lines of neutral boron in solar-type stellar atmospheres is investigated taking into account effects of departures from local thermodynamic equilibrium (NLTE effects). The latter are due to a combination of…
Oxygen is a powerful tracer element of Galactic chemical evolution. Unfortunately, only a few oxygen lines are available in the ultraviolet-infrared stellar spectra for the reliable determination of its abundance. Moreover, oxygen…
LTE abundances of light elements in extremely metal-poor (EMP) stars have been previously derived from high quality spectra. New derivations, free from the NLTE effects, will better constrain the models of the Galactic chemical evolution…
Aims: Aluminium is a key element to constrain the models of the chemical enrichment and the yields of the first supernovae. But obtaining precise Al abundances in extremely metal-poor (EMP) stars requires that the non-LTE effects be…
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…
We investigate the effects of horizontal radiative transfer (RT) a NLTE on important diagnostic iron lines in a realistic 3-D HD simulation. Using a multi-level atom we compute and compare widely used Fe I line profiles at 3 different…
Motivated by the measurement of redshifted Fe H$\alpha$ lines during type I X-ray bursts on EXO 0748-676 (Cottam, Paerels & Mendez), we study the formation of atomic Fe lines above the photosphere of a bursting neutron star ($k_BT_{\rm eff}…
Nitrogen is an important element in various fields of stellar and Galactic astronomy, and the solar nitrogen abundance is crucial as a yardstick for comparing different objects in the cosmos. In order to obtain a precise and accurate value…
The NLTE effects affecting oxygen-abundance determinations of solar-type stars are discussed. LTE is perfectly safe for the forbidden lines. The permitted triplet at 777 nm is expected to show NLTE effects on the order of a few tenths of a…
We analyze the ratios of the broad hydrogen Balmer emission lines (from H\alpha to H\epsilon) in the context of estimating the physical conditions in the broad line region (BLR) of active galactic nuclei (AGN). The Balmer emission lines are…
The excitation of H ($1s-2s$) by electron impact in the presence and in the absence of the laser field is studied in the framework of the first Born approximation. The angular variation of the laser-assisted differential cross section (DCS)…
The observed H$_2$ line ratios in OMC--1 and IC443 are not satisfactorily explained by conventional shock excitation models. We consider the microscopic collisional processes implicit in ambipolar diffusion models of magnetised C-shocks and…