Including all the lines: data releases for spectra and opacities

2017 ◽  
Vol 95 (9) ◽  
pp. 825-827 ◽  
Author(s):  
Robert L. Kurucz
Keyword(s):  
Energy Levels ◽  
Model Atmosphere ◽  
Stellar Atmosphere ◽  
Progress Report ◽  
Atomic Line ◽  
Radiation Hydrodynamics ◽  
Stellar Spectra ◽  
Stellar Interior ◽  
Laboratory Source ◽  
Spectrum Synthesis

I present a progress report on including all the lines in the line lists, including all the lines in the opacities, and including all the lines in the model atmosphere and spectrum synthesis calculations. The increased opacity will improve stellar atmosphere, pulsation, stellar interior, asteroseismology, nova, supernova, and other radiation-hydrodynamics calculations. At present I have produced atomic line data for computing opacities for 544 million lines for elements up through Zn. Of these, 2.11 million lines are between known energy levels so have good wavelengths for computing spectra. Work is continuing on heavier elements. I also report on using stellar spectra as the laboratory source for extending analyses to higher energy levels. Data for each ion and merged line lists are available on my website kurucz.harvard.edu .

Including all the lines1This article is part of a Special Issue on the 10th International Colloquium on Atomic Spectra and Oscillator Strengths for Astrophysical and Laboratory Plasmas.

2011 ◽  
Vol 89 (4) ◽  
pp. 417-428 ◽  
Author(s):  
Robert L. Kurucz
Keyword(s):  
Energy Levels ◽  
Model Atmosphere ◽  
Stellar Atmosphere ◽  
Oscillator Strengths ◽  
High Signal ◽  
Radiation Hydrodynamics ◽  
International Colloquium ◽  
Laboratory Plasmas ◽  
Laboratory Spectrum ◽  
Spectrum Synthesis

I present a progress report on including all the lines in the line lists, including all the lines in the opacities, and including all the lines in the model atmosphere and spectrum synthesis calculations. The increased opacity will improve stellar atmosphere, pulsation, stellar interior, asteroseismology, nova, supernova, and other radiation-hydrodynamics calculations. I also report on producing high-resolution, high-signal-to-noise atlases for use in verifying the line data and spectrum calculations, and as tools for extending laboratory spectrum analyses to higher energy levels. All the data are available on my web site: kurucz.harvard.edu .

scholarly journals The Belgian repository of fundamental atomic data and stellar spectra

2017 ◽  
Vol 95 (9) ◽  
pp. 833-839 ◽  
Author(s):  
A. Lobel ◽  
P. Royer ◽  
C. Martayan ◽  
M. Laverick ◽  
T. Merle ◽  
...  
Keyword(s):  
Atomic Line ◽  
Atomic Data ◽  
High Signal ◽  
Atmospheric Parameter ◽  
Synthetic Spectrum ◽  
Signal To Noise ◽  
Stellar Spectra ◽  
Novel Approach ◽  
Spectrum Synthesis ◽  
Quality Assessments

BRASS is an international networking project of the Federal Government of Belgium for the development of a new public database providing accurate fundamental atomic data of vital importance for stellar spectroscopic research. The BRASS database will offer atomic line data that is thoroughly tested by comparing theoretical and observed stellar spectra. We are in the course of performing extensive quality assessments of selected atomic input data with advanced radiative transfer spectrum synthesis calculations that we compare in detail to high-resolution Mercator-HERMES and ESO-VLT-UVES spectra of very high signal-to-noise ratios for about 30 hot and cool bright stars of B, A, F, G, and K spectral types. The new database will provide the tested and validated values of absorption lines we retrieve from various existing atomic repositories, such as NIST and VAMDC. The validated atomic datasets, combined with the observed and theoretical spectra, will be interactively offered online at brass.sdf.org. The combination of these datasets is a novel approach for its development, which will provide a universal reference for advanced stellar spectroscopic research. We present the atmospheric parameter results of a subset of five benchmark stars observed with signal-to-noise ratios of 800–1200. The observed and theoretical spectra of the Sun and 51 Peg between 4000 and 6800 Å are offered online in the BRASS Data Interface. It also incorporates a new list of ∼900 metal lines for which we compute blending below 5% of the equivalent width useful for detailed line profile modeling and synthetic spectrum fit quality assessments of atomic line data.

Atomic line shapes in stellar spectra

2008 ◽  
Author(s):  
John F. Kielkopf ◽  
Nicole F. Allard ◽  
Marco Antonio Gigosos ◽  
Manuel Ángel González
Keyword(s):  
Atomic Line ◽  
Stellar Spectra ◽  
Line Shapes

scholarly journals Influence of Abundances Upon Stellar Atmosphere Calculations

1976 ◽  
Vol 72 ◽  
pp. 3-15
Author(s):  
B. Baschek
Keyword(s):  
Model Atmosphere ◽  
Stellar Atmosphere ◽  
Theoretical Spectrum ◽  
Differential Analysis ◽  
Absorption Coefficients ◽  
Quantitative Classification ◽  
Element Abundances ◽  
Scattering Coefficients ◽  
Basic Equations ◽  
Bolometric Correction

The basic equations for constructing a stellar atmosphere (hydrostatic equilibrium, flux constancy, radiative transfer, convective instability) are briefly summarized. While the parameters Teff (effective temperature) and g (surface gravity) are directly contained in these equations, the element abundances ∈i enter only indirectly through the thermodynamic properties (such as electron pressure, entropy, …) and the absorption and scattering coefficients of stellar matter.The equation of state, convection, the effects of the absorption coefficients (particularly of line absorption) on the temperature stratification, and the role of velocity fields (microturbulence) are discussed in some detail, emphasizing their dependence on the abundances.From a given model atmosphere, a ‘theoretical spectrum’ (colours, bolometric correction, line strengths etc.) can be calculated. The (relative) fluxes emerging at the surface are essentially determined by the temperature gradient and the absorption coefficients at the frequencies under consideration. The basic goal of quantitative classification, however, is the inverse problem, namely to deduce the stellar parameters from selected observed spectral criteria. Aspects relevant to this problem such as the question of uniqueness and the occurrence of possible systematic errors (even when using differential analysis techniques) are briefly sketched and illustrated by some examples.

Some Applications of Model Atmospheres

1974 ◽  
Vol 2 (5) ◽  
pp. 230-235
Author(s):  
M. S. Bessell
Keyword(s):  
White Dwarf ◽  
Model Atmosphere ◽  
Stellar Atmosphere ◽  
List Type ◽  
Cool Star ◽  
Abundance Patterns ◽  
Synthetic Spectra

In the five years since the last invited paper on model stellar atmosphere applications there have been many significant advances made on all fronts. The five aspects which I will cover in this paper are: (1) the results of white dwarf model atmosphere investigations;(2) the results of the inclusion of non LTE phenomena in the atmosphere computations of hot (T > 15,000 K) stars;(3) the probable understanding of the cause of peculiar abundance patterns in the Ap and Bp and Am stars;(4) the advances in theory and observations of cool star atmospheres; and(5) the use of synthetic spectra and colours.

scholarly journals Recent advances in non-LTE stellar atmosphere models

2016 ◽  
Vol 12 (S329) ◽  
pp. 215-222
Author(s):  
Andreas A. C. Sander
Keyword(s):  
Massive Star ◽  
Model Atmosphere ◽  
Quantitative Information ◽  
Stellar Atmosphere ◽  
Stellar Atmospheres ◽  
Stellar Winds ◽  
Next Generation ◽  
Wide Range ◽  
Sophisticated Model ◽  
Current Stage

AbstractIn 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 stellar parameters. The intricate non-LTE conditions in stellar winds dictate the development of adequate sophisticated model atmosphere codes. The increase in both, the computational power and our understanding of physical processes in stellar atmospheres, led to an increasing complexity in the models. As a result, codes emerged that can tackle a wide range of stellar and wind parameters.After a brief address of the fundamentals of stellar atmosphere modeling, the current stage of clumped and line-blanketed model atmospheres will be discussed. Finally, the path for the next generation of stellar atmosphere models will be outlined. Apart from discussing multi-dimensional approaches, I will emphasize on the coupling of hydrodynamics with a sophisticated treatment of the radiative transfer. This next generation of models will be able to predict wind parameters from first principles, which could open new doors for our understanding of the various facets of massive star physics, evolution, and death.

scholarly journals Joint Discussion 10: 3D views on cool stellar atmospheres – theory meets observation

2009 ◽  
Vol 5 (H15) ◽  
pp. 331-343
Author(s):  
K.N. Nagendra ◽  
P. Bonifacio ◽  
H.-G. Ludwig
Keyword(s):  
Chemical Composition ◽  
High Efficiency ◽  
Big Bang ◽  
Stellar Atmosphere ◽  
Stellar Atmospheres ◽  
Stellar Spectra ◽  
Low Mass ◽  
Computational Resources ◽  
The Big Bang ◽  
The Universe

Much of what we know about the chemical composition of the Universe actually stems from the chemical composition of stars, which is often deciphered from the spectra emerging from their atmospheres. Cool, low-mass and long-living stars allow to study the evolution of the Universe's chemistry from a time shortly after the big bang until today. The observation and interpretation of stellar spectra is a classical field in astronomy but is still undergoing vivid developments. The enormous increase in available computational resources opened-up possibilities which led to a revolution in the degree of realism to which modelers can mimic Nature. High-resolution, high-stability, high-efficiency spectrographs are now routinely providing stellar spectra whose full information content can only be exploited if a very much refined description of a stellar atmosphere is at hand.

scholarly journals Presentation and Interpretation of High Resolution Infrared Spectra of Late-Type Stars

1974 ◽  
Vol 3 ◽  
pp. 255-268 ◽  
Author(s):  
R. I. Thompson
Keyword(s):  
Stellar Evolution ◽  
Carbon Star ◽  
Stellar Atmosphere ◽  
Stellar Atmospheres ◽  
Stellar Spectra ◽  
Cool Star ◽  
Convective Mixing ◽  
Processed Material ◽  
Carbon Compounds ◽  
Red Giant

Current interest in stellar evolution is concentrated on the life of a star after it has left the main sequence. Of particular interest are the red giant or supergiant periods during the hydrogen and helium shell burning phases. Convective mixing during these stages can mix nuclear processed material to the surface where it may be viewed by spectroscopic methods. It is imperative that this rare chance to view processed material be exploited fully to increase our knowledge of stellar evolution.The observation and interpretation of cool star spectra has its own particular set of problems and advantages. A particular difficulty is the formation of molecules at the low temperatures which occur in the atmospheres of late stars. Not only must the particularly complex spectra of molecules be dealt with but the problem of chemical equilibrium in the atmosphere must be solved accurately before quantitative analysis may be performed. The formation of molecules, however, has one advantage in that it very dramatically separates those stars with carbon to oxygen ratios greater than one from those with ratios less than one. It is the very high dissociation energy of 11.1 eV for the CO molecule which performs this separation. If carbon is less abundant than oxygen all of the carbon is tied up in CO and only oxides are formed in the stellar atmosphere which produce typical M star spectra. If, however, carbon is more abundant than oxygen then carbon compounds such as C2 are formed in place of the oxides and a carbon star spectrum is formed. One of the great advantages of infrared stellar spectra is that it is the only ground based technique for observing CO in stellar atmospheres.

scholarly journals Modeling the Hα Emission Surrounding Spica Using the Lyman Continuum from a Gravity-darkened Central Star

2021 ◽  
Vol 923 (1) ◽  
pp. 10
Author(s):  
Jason P. Aufdenberg ◽  
Joseph M. Hammill
Keyword(s):  
Surface Brightness ◽  
Central Star ◽  
Model Atmosphere ◽  
Stellar Atmosphere ◽  
Primary Star ◽  
Near Ir ◽  
Lyman Continuum ◽  
Sky Survey ◽  
Hα Emission ◽  
Star Binary

Abstract The large, faint Hα emission surrounding the early B-star binary Spica has been used to constrain the total hydrogen recombination rate of the nebula and indirectly probe the Lyman continuum luminosity of the primary star. Early analysis suggested that a stellar atmosphere model, consistent with Spica A’s spectral type, has a Lyman continuum luminosity about two times lower than required to account for the measured Hα surface brightness within the nebula. To more consistently model both the stellar and nebular emission, we have used a model atmosphere for Spica A that includes the effects of gravity darkening as input to photoionization models to produce synthetic Hα surface brightness distributions for comparison to data from the Southern Hα Sky Survey Atlas. This paper presents a method for the computation of projected surface brightness profiles from 1D volume emissivity models and constrains both stellar and nebular parameters. A mean effective temperature for Spica A of ≃24,800 K is sufficient to match both the observed absolute spectrophotometry, from the far-UV to the near-IR, and radial Hα surface brightness distributions. Model hydrogen densities increase with the distance from the star, more steeply and linearly toward the southeast. The northwest matter-bounded portion of the nebula is predicted to leak ∼17% of Lyman continuum photons. Model H ii region column densities are consistent with archival observations along the line of sight.

scholarly journals NLTE spectral analysis of the intermediate helium-rich subdwarf B star CPD−20°1123

2020 ◽  
Vol 497 (1) ◽  
pp. 67-80 ◽  
Author(s):  
L Löbling
Keyword(s):  
Optical Spectrum ◽  
Local Thermodynamic Equilibrium ◽  
Model Atmosphere ◽  
Stellar Atmosphere ◽  
Light Metals ◽  
Helium Burning ◽  
Number Ratio ◽  
Metal Abundances ◽  
Non Local ◽  
Intermediate Surface

ABSTRACT Subdwarf B (sdB) stars are core helium-burning stars with stratified atmospheres. Their atmospheres are dominated by hydrogen (H) while the helium (He) and metal abundances are shaped by an interplay of gravitational settling and radiative levitation. However, a small fraction of these show spectra dominated by He i absorption lines. In between these groups of He-deficient and extreme He-rich sdBs, some are found to have intermediate surface He abundances. These objects are proposed to be young ‘normal’ (He-deficient) sdBs for which the dynamical stratification of the atmosphere is still ongoing. We present an analysis of the optical spectrum of such an intermediate He-rich sdB, namely CPD−20°1123, by means of non-local thermodynamic equilibrium (NLTE) stellar atmosphere models. It has a He-to-H number ratio of He/H = 0.13 ± 0.05 and its effective temperature of $\mbox{$T_\mathrm{eff}$} = 25\, 500 \pm 1000 \, \mathrm{K}$ together with a surface gravity of $\log \, (g$ / cm s−2) = 5.3 ± 0.3 places the star close to the high-temperature edge until which it may be justified to use LTE model atmospheres. This work states a test of the Tübingen NLTE Model Atmosphere Package for this temperature regime. We present the first application of revised, elaborated model atoms of low ionization stages of light metals usable with this atmosphere code.

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