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.

scholarly journals The Belgian Repository of Fundamental Atomic Data and Stellar Spectra (BRASS)

Atoms ◽  
2019 ◽  
Vol 7 (4) ◽  
pp. 105
Author(s):  
Alex Lobel ◽  
Pierre Royer ◽  
Christophe Martayan ◽  
Michael Laverick ◽  
Thibault Merle ◽  
...  
Keyword(s):  
User Interaction ◽  
Electronic Configuration ◽  
Atomic Data ◽  
High Signal ◽  
Stellar Spectra ◽  
Novel Approach ◽  
New Public ◽  
Spectrum Synthesis ◽  
Atomic Lines ◽  
Width Measurements

Background: BRASS (Belgian Repository of Fundamental Atomic Data and Stellar Spectra) is an international networking project for the development of a new public database providing accurate fundamental atomic data of vital importance for stellar spectroscopic research. We present an overview of research results obtained in the past four years. Methods: The BRASS database offers atomic line data we thoroughly tested by comparing theoretical and observed stellar spectra. We perform extensive quality assessments of selected atomic input data using advanced radiative transfer spectrum synthesis calculations, which we compare to high-resolution Mercator-HERMES and ESO-VLT-UVES spectra of F-, G-, and K-type benchmark stars observed with very high signal-to-noise ratios. We have retrieved about half a million atomic lines required for our detailed spectrum synthesis calculations from the literature and online databases such as VAMDC, NIST, VALD, CHIANTI, Spectr-W 3 , TIPbase, TOPbase, SpectroWeb. Results: The atomic datasets have been cross-matched based on line electronic configuration information and organized in a new online repository called BRASS. The validated atomic data, combined with the observed and theoretical spectra are also interactively offered in BRASS. The combination of these datasets is a novel approach for its development providing a universal reference for advanced stellar spectroscopic research. Conclusion: We present an overview of the BRASS Data Interface developments allowing online user interaction for the combined spectrum and atomic data display, line identification, atomic data accuracy assessments including line log(gf)-values, and line equivalent width measurements.

scholarly journals The Belgian Repository of fundamental Atomic data and Stellar Spectra (BRASS)

2019 ◽  
Vol 15 (S350) ◽  
pp. 386-387
Author(s):  
M. Laverick ◽  
A. Lobel ◽  
P. Royer ◽  
T. Merle ◽  
C. Martayan ◽  
...  
Keyword(s):  
Quality Assessment ◽  
State Of The Art ◽  
Oscillator Strengths ◽  
Atomic Data ◽  
Synthetic Spectrum ◽  
High Quality ◽  
Data Repositories ◽  
Stellar Spectra ◽  
Atomic Transitions ◽  
Stellar Spectroscopy

AbstractThe Belgian Repository of fundamental Atomic data and Stellar Spectra (BRASS) aims to provide one of the largest systematic and homogeneous quality assessment to date of literature atomic data required for stellar spectroscopy. By comparing state-of-the-art synthetic spectrum calculations with extremely high-quality observed benchmark spectra, we have critically evaluated fundamental atomic data, such as line wavelengths and oscillator strengths, for thousands of astrophysically-relevant transitions found in the literature and across several major atomic data repositories. These proceedings provide a short overview of the BRASS project to date, highlighting our recent efforts to investigate and quality-assess the atomic literature data pertaining to over a thousand atomic transitions present in FGK-type stellar spectra. BRASS provides all quality assessed data, theoretical spectra, and observed spectra in a new interactive database under development at brass.sdf.org.

scholarly journals NGC 6302: high-ionization permitted lines. Applying X-SSN synthesis to VLT-UVES spectra

2011 ◽  
Vol 7 (S283) ◽  
pp. 470-471
Author(s):  
Daniel Péquignot ◽  
Christophe Morisset ◽  
Simon Casassus
Keyword(s):  
High Signal ◽  
Signal To Noise ◽  
High Ionization ◽  
Spectrum Synthesis ◽  
First Time

AbstractA preliminary VLT-UVES spectrum of NGC 6302 (Casassus et al. 2002, MN), which hosts one of the hottest PN nuclei known (Teff ~ 220000 K; Wright et al. 2011, MN), has been recently analysed by means of X-SSN, a spectrum synthesis code for nebulae (Morisset and Péquignot). Permitted recombination lines from highly-ionized species are detected/identified for the first time in a PN, and some of them probably for the first time in (astro)physics. The need for a homogeneous, high signal-to-noise UVES spectrum for NGC 6302 is advocated.

scholarly journals Beryllium abundances along the evolutionary sequence of the open cluster IC 4651

2009 ◽  
Vol 5 (S268) ◽  
pp. 357-358 ◽  
Author(s):  
Rodolfo Smiljanic ◽  
L. Pasquini ◽  
C. Charbonnel ◽  
N. Lagarde
Keyword(s):  
Main Sequence ◽  
Open Cluster ◽  
High Signal ◽  
Evolutionary Sequence ◽  
Main Sequence Stars ◽  
Signal To Noise ◽  
Mixing Processes ◽  
Hydrodynamical Models ◽  
Spectrum Synthesis ◽  
Hertzsprung Gap

AbstractThe simultaneous investigation of Li and Be in stars is a powerful tool in the study of the evolutionary mixing processes. Here, we present beryllium abundances in stars along the whole evolutionary sequence of the open cluster IC 4651. This cluster has a metallicity of [Fe/H] = +0.11 and an age of 1.2 or 1.7 Gyr. Abundances have been determined from high-resolution, high signal-to-noise UVES spectra using spectrum synthesis and model atmospheres. Lithium abundances for the same stars were determined in a previous work. Confirming previous results, we find that the Li dip is also a Be dip. For post-main-sequence stars, the Be dilution starts earlier within the Hertzsprung gap than expected from classical predictions, as does the Li dilution. Theoretical hydrodynamical models are able to reproduce well all the observed features.

scholarly journals Needs for Atomic Data for Quantitative Analysis of Stellar Spectra

1983 ◽  
Vol 6 ◽  
pp. 781-787 ◽  
Author(s):  
B. Baschek
Keyword(s):  
Quantitative Analysis ◽  
Model Atmosphere ◽  
High Spectral Resolution ◽  
Iteration Step ◽  
Atomic Data ◽  
Synthetic Spectrum ◽  
Theoretical Spectrum ◽  
Stellar Spectrum ◽  
Stellar Spectra ◽  
Element Abundances

The goal of a quantitative analysis of a stellar spectrum is to derive the physical and chemical state of the stellar atmosphere, i.e. by definition the region emitting the spectrum. Of particular interest are the element abundances, they have to be determined together with the temperatures and densities (pressures) in the atmosphere. A detailed analysis usually is an iterative procedure: a model atmosphere is constructed from reasonable starting values of the parameters (effective temperature, surface gravity, element abundances,...) and used to calculate a theoretical, “synthetic” spectrum. By comparing the observed with the theoretical spectrum, improved stellar parameters are gained for the next iteration step.Ideally, all atomic data entering the analysis should be known with sufficient accuracy, i.e. errors in the analysis should be due to uncertainties in the assumptions of the models, in the treatment of the velocity fields etc., and not due to insufficient atomic data. In the last decade, the ultraviolet portion of the spectrum below λ ≲ 3200 Å has become accessible by satellites such as Copernicus and the International Ultraviolet Explorer (IUE) with high spectral resolution. Studies of stellar spectra in this new range have revealed the needs for a large amount of atomic data required for the analyses.

scholarly journals Limitations of Stellar Abundance Determinations

1991 ◽  
Vol 145 ◽  
pp. 39-47
Author(s):  
B. Baschek
Keyword(s):  
Main Sequence ◽  
Signal To Noise Ratio ◽  
Model Atmosphere ◽  
Atomic Data ◽  
Synthetic Spectrum ◽  
Main Sequence Stars ◽  
Stellar Spectra ◽  
Perfect Model ◽  
Main Factors ◽  
The Continuum

The information content of (photospheric) stellar spectra and the accuracy of abundance determinations are discussed. Besides the physical properties of the line spectra, the spectral resolution, the signal-to-noise ratio, but also the incompleteness of the knowledge of the contributing blends limit the abundance information. For a perfect model atmosphere the main factors determining the accuracy of the abundances are S/N, the line saturation, and the location of the continuum (or, in a synthetic spectrum, the background of numerous lines). In addition systematic errors introduced by missing atomic data and an imperfect model atmosphere (non-LTE, line blanketing, hydrodynamics) are important. The typical accuracy of abundance determinations is discussed for main sequence stars for which the most reliable data are available, and for a few selected other stellar types.

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 .

BRASS: Cross-match of atomic repositories and spectral line blending investigations

2017 ◽  
Vol 95 (9) ◽  
pp. 843-846 ◽  
Author(s):  
M. Laverick ◽  
A. Lobel ◽  
P. Royer ◽  
C. Martayan ◽  
T. Merle
Keyword(s):  
Spectral Line ◽  
State Of The Art ◽  
Spectral Synthesis ◽  
Atomic Data ◽  
High Quality ◽  
Stellar Spectra ◽  
Synthetic Spectra ◽  
Atomic Lines ◽  
Quality Assessments ◽  
Cross Match

The Belgian repository of fundamental atomic data and stellar spectra (BRASS) aims to critically evaluate atomic data, from publicly available repositories, by comparing state-of-the-art synthetic spectra against high-quality benchmark stellar spectra. In preparation for our assessment we have cross-matched atomic line transitions from several different databases. Our investigation revealed significant updates in log(gf) values, sometimes as large as 2–4 dex, that fully justify the need for systematic quality assessments of the atomic data. We have also investigated the spectral line blending of an initial subset of 2647 atomic lines using spectral synthesis calculations, for the spectral types BAFGK.

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

2018 ◽  
Vol 612 ◽  
pp. A60 ◽  
Author(s):  
M. Laverick ◽  
A. Lobel ◽  
T. Merle ◽  
P. Royer ◽  
C. Martayan ◽  
...  
Keyword(s):  
Spectral Lines ◽  
Oscillator Strengths ◽  
Atomic Line ◽  
Atomic Data ◽  
Stellar Spectra ◽  
Line List ◽  
The Impact ◽  
Cross Match ◽  
Atomic Parameters ◽  
Non Parametric

Context. Fundamental atomic parameters, such as oscillator strengths, play a key role in modelling and understanding the chemical composition of stars in the Universe. Despite the significant work underway to produce these parameters for many astrophysically important ions, uncertainties in these parameters remain large and can propagate throughout the entire field of astronomy. Aims. The Belgian repository of fundamental atomic data and stellar spectra (BRASS) aims to provide the largest systematic and homogeneous quality assessment of atomic data to date in terms of wavelength, atomic and stellar parameter coverage. To prepare for it, we first compiled multiple literature occurrences of many individual atomic transitions, from several atomic databases of astrophysical interest, and assessed their agreement. In a second step synthetic spectra will be compared against extremely high-quality observed spectra, for a large number of BAFGK spectral type stars, in order to critically evaluate the atomic data of a large number of important stellar lines. Methods. Several atomic repositories were searched and their data retrieved and formatted in a consistent manner. Data entries from all repositories were cross-matched against our initial BRASS atomic line list to find multiple occurrences of the same transition. Where possible we used a new non-parametric cross-match depending only on electronic configurations and total angular momentum values. We also checked for duplicate entries of the same physical transition, within each retrieved repository, using the non-parametric cross-match. Results. We report on the number of cross-matched transitions for each repository and compare their fundamental atomic parameters. We find differences in log(gf) values of up to 2 dex or more. We also find and report that ~2% of our line list and Vienna atomic line database retrievals are composed of duplicate transitions. Finally we provide a number of examples of atomic spectral lines with different retrieved literature log(gf) values, and discuss the impact of these uncertain log(gf) values on quantitative spectroscopy.

scholarly journals 12C/13C ratios in giants of open clusters

2006 ◽  
Vol 2 (S239) ◽  
pp. 298-300
Author(s):  
Rodolfo Smiljanic ◽  
R. Gauderon ◽  
P. North ◽  
B. Barbuy ◽  
C. Charbonnel ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Isotopic Ratio ◽  
Open Clusters ◽  
High Signal ◽  
Signal To Noise ◽  
Hydrogen Burning ◽  
Carbon Isotopic Ratio ◽  
Carbon Isotopic ◽  
Spectrum Synthesis ◽  
Convective Layer

AbstractThe carbon isotopic ratio,12C/13C, is a tracer of the mixing events during the evolution along the giant branch, due to the conversion of12C into13C (and14N) via the CN cycle. A decrease of this ratio from 90, the solar value, to 20–25, is expected due to the first dredge-up. However, ratios down to 3–4, the CN cycle equilibrium value, have been observed in giants of the field, of globular and of open clusters. Observations seem to indicate a non-standard mixing in the RGB, probably beginning in the luminosity bump, when the outward moving hydrogen burning shell crosses the molecular weight barrier left by the convective layer in its maximum extent. We are currently analyzing a sample of 24 giants in 8 open clusters for which we determined12C/13C from high resolution, high signal to noise spectra using spectrum synthesis. In this work we discuss the general characteristics of our results in comparison to previous analyses of giants in open clusters available in the literature.

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