相关论文: NLTE water lines in Betelgeuse-like atmospheres
The structures of the outer atmospheres of red giants are very complex. The notion of large optically thick molecular spheres around the stars (MOLspheres) has been invoked in order to explain e.g. spectro-interferometric observations.…
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…
Understanding the dynamics of the solar chromosphere is crucial to understanding energy transport across the solar atmosphere. The chromosphere is optically thick at many wavelengths and described by non-local thermodynamic equilibrium…
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…
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…
The outer atmosphere of the M supergiant Betelgeuse is puzzling. Published observations of different kinds have shed light on different aspects of the atmosphere, but no unified picture has emerged. They have shown, for example, evidence of…
Context - Exoplanetary upper atmospheres are low density environments where radiative processes can compete with collisional ones and introduce non-local thermodynamic equilibrium (NLTE) effects into transmission spectra. Aims - We develop…
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…
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…
The atmospheres of novae at early times in their outbursts are very extended, expanding shells with low densities. Models of these atmospheres show that NLTE effects are very important and must be included in realistic calculations. We…
Present observational techniques provide stellar spectra with high resolution at a high signal-to-noise ratio over the complete wavelength range -- from the far infrared to the X-ray. NLTE effects are particularly important for hot stars,…
One of the major tasks in interpretation of data from large-scale stellar surveys is to determine the fundamental atmospheric parameters such as effective temperature, surface gravity, and metallicity. In most on-going and upcoming…
Several recent papers have argued for warm, semi-detached, molecular layers surrounding red giant and supergiant stars, a concept known as a MOLsphere. Spectroscopic and interferometric analyses have often corroborated this general picture.…
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…
Different simplified approaches are used to account for the non-local thermodynamic equilibrium (NLTE) effects with 3D hydrodynamical model atmospheres. In certain cases, chemical abundances are derived in 1D NLTE and corrected for the 3D…
In the last decades, stellar atmosphere models have become a key tool in understanding massive stars. Applied for spectroscopic analysis, these models provide quantitative information on stellar wind properties as well as fundamental…
Basic assumptions of the NLTE approximation in stellar atmospheres are summarized. The assumptions of thermodynamic equilibrium, local thermodynamic equilibrium (LTE), and non-LTE (NLTE) are compared. It is emphasized that LTE is a poor…
Context. Obtaining precise stellar and wind properties and abundance patterns of massive stars is crucial to understanding their nature and interactions with their environments, as well as to constrain their evolutionary paths and…
We present new or improved methods for calculating NLTE, line-blanketed model atmospheres for hot stars with winds (spectral types A to O), with particular emphasis on a fast performance. These methods have been implemented into a previous,…
Supernovae, with their diversity of compositions, velocities, envelope masses, and interactions are good testing grounds for probing the importance of NLTE in expanding atmospheres. In addition to treating H, He, Li I, O I, Ne I, Na I, and…