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

2019 ◽  
Vol 624 ◽  
pp. A60 ◽  
Author(s):  
M. Laverick ◽  
A. Lobel ◽  
P. Royer ◽  
T. Merle ◽  
C. Martayan ◽  
...  
Keyword(s):  
Quality Assessment ◽  
Large Scale ◽  
Spectral Lines ◽  
Oscillator Strengths ◽  
Atomic Data ◽  
Chemical Abundance ◽  
Stellar Spectra ◽  
Atomic Lines ◽  
The Universe ◽  
Selection Of

Context. Fundamental atomic transition parameters, such as oscillator strengths and rest wavelengths, play a key role in modelling and understanding the chemical composition of stars in the universe. Despite the significant work under way to produce these parameters for many astrophysically important ions, uncertainties in these parameters remain large and can limit the accuracy of chemical abundance determinations.Aims. The Belgian repository of fundamental atomic data and stellar spectra (BRASS) aims to provide a large systematic and homogeneous quality assessment of the atomic data available for quantitative spectroscopy. BRASS shall compare synthetic spectra against extremely high-quality observed spectra, at a resolution of ∼85 000 and signal-noise ratios of ∼1000, for approximately 20 bright BAFGK spectral-type stars, in order to critically evaluate the atomic data available for over a thousand potentially useful spectral lines.Methods. A large-scale homogeneous selection of atomic lines is performed by synthesising theoretical spectra of literature atomic lines for FGK-type stars including the Sun, resulting in a selection of 1091 theoretically deep and unblended lines in the wavelength range 4200–6800 Å, which may be suitable for quality assessment. Astrophysical log(g f) values are determined for the 1091 transitions using two commonly employed methods. The agreement of these log(g f) values are used to select well-behaved lines for quality assessment.Results. We found 845 atomic lines to be suitable for quality assessment, of which 408 were found to be robust against systematic differences between analysis methods. Around 53% of the quality-assessed lines were found to have at least one literature log(g f) value in agreement with our derived values, though the remaining values can disagree by as much as 0.5 dex. Only ∼38% of Fe Ilines were found to have sufficiently accurate log(g f) values, increasing to ∼70–75% for the remaining Fe-group lines.

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.

Non-local thermodynamical equilibrium abundance analysis of singly ionized praseodymium for the Sun

2020 ◽  
Vol 496 (4) ◽  
pp. 5361-5371
Author(s):  
Abdelrazek M K Shaltout ◽  
Ali G A Abdelkawy ◽  
M M Beheary
Keyword(s):  
Spectral Lines ◽  
Oscillator Strengths ◽  
Atomic Data ◽  
Dimensional Model ◽  
Thermodynamical Equilibrium ◽  
Solar Abundance ◽  
One Dimensional ◽  
Microturbulent Velocity ◽  
Non Local ◽  
Local Thermodynamical Equilibrium

ABSTRACT Determinations of the solar abundance of praseodymium (Pr) depend critically on the local thermodynamical equilibrium (LTE) and non-local thermodynamical equilibrium (NLTE) techniques beyond the capabilities of a classical one-dimensional model atmosphere. Here, in this analysis, we adopt an atomic model atom of Pr consisting of 105 energy levels and 14 bound–bound transitions of singly ionized praseodymium (Pr ii) and the ground state of the Pr iii continuum limit. We briefly analyse the solar abundance of Pr taking the solar model atmospheres of Holweger & Müller (1974, Solar Physics, 39, 19) with the measured equivalent linewidths and invoking a microturbulent velocity treatment. We succeed in accurately selecting nearby clear sections of the spectrum for 14 spectral lines of Pr ii with the improved atomic data of high-quality oscillator strengths available from the laboratory measurements of several possible sources as well as accurate damping constants successfully determined from the literature. We find a Pr abundance revised to be downwards log ϵPr(NLTE) = 0.75 ± 0.09, which is in good agreement with the meteoritic value (log ϵPr = 0.76 ± 0.03). A comparison of the NLTE abundance corrections with the standard LTE analysis, log ϵPr(LTE) = 0.74 ± 0.08, reveals a positive correction of  +0.01 dex, estimated from the selected solar Pr ii lines. The Pr abundance value is clearly superior following the classical one-dimensional model atmospheres of Holweger & Müller, the absolute scales of gf-values, the microturbulent velocity and the adopted equivalent linewidths.

scholarly journals Laboratory astrophysics for the interpretation of stellar spectra

2019 ◽  
Vol 15 (S350) ◽  
pp. 345-349
Author(s):  
Ulrike Heiter
Keyword(s):  
Milky Way ◽  
Chemical Elements ◽  
Spectral Lines ◽  
Laboratory Astrophysics ◽  
Atomic Data ◽  
Milky Way Galaxy ◽  
Infrared Wavelength ◽  
Stellar Spectra ◽  
Continuous Activities ◽  
Host Stars

AbstractHigh-resolution stellar spectra are important tools for studying the chemical evolution of the Milky Way Galaxy, tracing the origin of chemical elements, and characterizing planetary host stars. Large amounts of data have been accumulating, in particular in the optical and infrared wavelength regions. The observed spectral lines are interpreted using model spectra that are calculated based on transition data for numerous species, in particular neutral and singly ionized atoms. We rely heavily on the continuous activities of laboratory astrophysics groups that produce high-quality experimental and theoretical atomic data for the relevant transitions. We give examples for the precision with which the chemical composition of stars observed by different surveys can be determined, and discuss future needs from laboratory astrophysics.

The chemical composition of the sun1This review 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. 327-331 ◽  
Author(s):  
N. Grevesse ◽  
M. Asplund ◽  
A.J. Sauval ◽  
P. Scott
Keyword(s):  
Chemical Elements ◽  
Molecular Data ◽  
Solar Neighborhood ◽  
Spectral Lines ◽  
Oscillator Strengths ◽  
Atomic Data ◽  
Solar Photosphere ◽  
International Colloquium ◽  
Laboratory Plasmas ◽  
Selection Of

We have very recently re-determined the abundances of nearly all the available chemical elements in the solar photosphere, from lithium to thorium (Asplund et al. Annu. Rev. Astron. Astrophys. 47, 481 (2009)). This new complete and homogeneous analysis results from a very careful selection of spectral lines of all the indicators of the abundances present in the solar photospheric spectrum, from a discussion of the atomic and molecular data, and from an analysis of these lines based on a new 3D model of the solar outer layers, taking non-LTE effects into account when possible. We present these new results, compare them with other recent solar data as well as with recent results for the solar neighborhood, and discuss some of their most important implications as well as some of the atomic data we still urgently need.

scholarly journals R-matrix electron-impact excitation data for the N-like iso-electronic sequence

2020 ◽  
Vol 643 ◽  
pp. A95
Author(s):  
Junjie Mao ◽  
N. R. Badnell ◽  
G. Del Zanna
Keyword(s):  
Electron Impact ◽  
Plasma Diagnostics ◽  
Spectral Lines ◽  
Impact Excitation ◽  
Electron Impact Excitation ◽  
Atomic Data ◽  
Astrophysical Plasma ◽  
Wide Range ◽  
The Impact ◽  
Effective Collision

Context. Spectral lines from N-like ions can be used to measure the temperature and density of various types of astrophysical plasmas. The atomic databases of astrophysical plasma modelling codes still have room for improvement in their electron-impact excitation data sets for N-like ions, especially for R-matrix data. This is particularly relevant for future observatories (e.g. Arcus), which will host high-resolution spectrometers. Aims. We aim to obtain level-resolved effective collision strengths for all transitions up to nl = 5d over a wide range of temperatures for N-like ions from O II to Zn XXIV (i.e. O+ to Zn23+) and to assess the accuracy of the present work. We also examine the impact of our new data on plasma diagnostics by modelling solar observations with CHIANTI. Methods. We carried out systematic R-matrix calculations for N-like ions, which included 725 fine-structure target levels in both the configuration interaction target and close-coupling collision expansions. The R-matrix intermediate coupling frame transformation method was used to calculate the collision strengths, while the AUTOSTRUCTURE code was used for the atomic structures. Results. We compare the present results for selected ions with those in archival databases and the literature. The comparison covers energy levels, oscillator strengths, and effective collision strengths. We show examples of improved plasma diagnostics when compared to CHIANTI models, which use only distorted wave data as well as some using previous R-matrix data. The electron-impact excitation data are archived according to the Atomic Data and Analysis Structure (ADAS) data class adf04 and will be available in OPEN-ADAS. The data can be used to improve the atomic databases for astrophysical plasma diagnostics.

Atomic data for stellar astrophysics: from the UV to the IR1This 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. 345-356 ◽  
Author(s):  
Glenn M. Wahlgren
Keyword(s):  
Hubble Space Telescope ◽  
Wavelength Region ◽  
Oscillator Strengths ◽  
Atomic Data ◽  
International Colloquium ◽  
Stellar Spectra ◽  
Optical Wavelength ◽  
Laboratory Plasmas ◽  
New Instrumentation ◽  
Made In

The study of stars and stellar evolution relies heavily on the analysis of stellar spectra. The need for atomic line data from the ultraviolet (UV) to the infrared (IR) regions is greater now than ever. In the past twenty years, the time since the launch of the Hubble Space Telescope, great progress has been made in acquiring atomic data for UV transitions. The optical wavelength region, now expanded by progress in detector technology, continues to provide motivation for new atomic data. In addition, investments in new instrumentation for ground-based and space observatories has lead to the availability of high-quality spectra at IR wavelengths, where the need for atomic data is most critical. In this review, examples are provided of the progress made in generating atomic data for stellar studies, with a look to the future for addressing the accuracy and completeness of atomic data for anticipated needs.

Accurate atomic data for Galactic Surveys

2017 ◽  
Vol 12 (S330) ◽  
pp. 203-205
Author(s):  
Maria Teresa Belmonte ◽  
Juliet C. Pickering ◽  
Christian Clear ◽  
Florence Liggings ◽  
Anne P. Thorne
Keyword(s):  
Fourier Transform ◽  
Spectroscopic Data ◽  
High Accuracy ◽  
Fourier Transform Spectroscopy ◽  
Oscillator Strengths ◽  
Atomic Data ◽  
Chemical Abundances ◽  
Atomic Parameters

AbstractFourier Transform spectroscopy is able to provide high accuracy atomic parameters needed by many ongoing galactic surveys. Our laboratory has carried out a study of the neutral iron spectrum over the last years to measure oscillator strengths much needed for the calculation of chemical abundances. The main aim of this contribution is to encourage further dialogue with astronomers regarding their current necessities of spectroscopic data, as this would help spectroscopists to prioritise present-day needs within the field.

scholarly journals Atomic data for PN analysis

1997 ◽  
Vol 180 ◽  
pp. 161-166
Author(s):  
P.J. Storey
Keyword(s):  
Electron Scattering ◽  
Cross Sections ◽  
Oscillator Strengths ◽  
Atomic Data ◽  
Resonance Phenomena ◽  
Theoretical Results ◽  
Powerful Electron ◽  
Selection Of ◽  
Atomic Parameters

This paper will review a selection of the work that has been published on the calculation of atomic parameters, relevant to PN, in the period since the 1992 Symposium. It will also attempt to address the accuracy of theoretical results, where possible. The review will concentrate primarily on results obtained using the powerful electron-scattering codes that describe resonance phenomena with ever increasing precision. Calculations of oscillator strengths and photoionisation cross-sections will not be discussed.

scholarly journals Stellar laboratories

2020 ◽  
Vol 637 ◽  
pp. A4
Author(s):  
T. Rauch ◽  
S. Gamrath ◽  
P. Quinet ◽  
M. Demleitner ◽  
M. Knörzer ◽  
...  
Keyword(s):  
Mass Fraction ◽  
Local Thermodynamic Equilibrium ◽  
Model Atmosphere ◽  
Spectral Lines ◽  
Oscillator Strengths ◽  
Atomic Data ◽  
Uv Spectrum ◽  
Hot Stars ◽  
Non Local ◽  
First Time

Context. Accurate atomic data is an essential ingredient for the calculation of reliable non-local thermodynamic equilibrium (NLTE) model atmospheres that are mandatory for the spectral analysis of hot stars. Aims. We aim to search for and identify for the first time spectral lines of copper (atomic number Z = 29) and indium (Z = 49) in hot white dwarf (WD) stars and to subsequently determine their photospheric abundances. Methods. Oscillator strengths of Cu IV–VII were calculated to include radiative and collisional bound-bound transitions of Cu in our NLTE model-atmosphere calculations. Oscillator strengths of In IV - VI were compiled from the literature. Results. We newly identified 1 Cu IV, 51 Cu V, 2 Cu VI, and 5 In V lines in the ultraviolet (UV) spectrum of DO-type WD RE 0503−289. We determined the photospheric abundances of 9.3 × 10−5 (mass fraction, 132 times solar) and 3.0 × 10−5 (56 600 times solar), respectively; we also found Cu overabundances in the DA-type WD G191−B2B (6.3 × 10−6, 9 times solar). Conclusions. All identified Cu IV-VI lines in the UV spectrum of RE 0503−289 were simultaneously well reproduced with our newly calculated oscillator strengths. With the detection of Cu and In in RE 0503−289, the total number of trans-iron elements (Z > 28) in this extraordinary WD reaches an unprecedented number of 18.

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