Laboratory astrophysics for the interpretation of stellar spectra

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.

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Atomic data for stellar spectroscopy

Proceedings of the International Astronomical Union ◽

10.1017/s174392131900509x ◽

2018 ◽

Vol 14 (A30) ◽

pp. 458-462

Author(s):

Ulrike Heiter

Keyword(s):

Chemical Elements ◽

Laboratory Astrophysics ◽

Atomic Data ◽

High Quality ◽

Milky Way Galaxy ◽

Infrared Wavelength ◽

Stellar Spectra ◽

Stellar Spectroscopy ◽

Routine Basis ◽

Continuous Activities

AbstractHigh-precision spectroscopy of large stellar samples plays a crucial role for several topical issues in astrophysics, such as studying the chemical evolution of the Milky Way Galaxy. Data are accumulating from instruments that obtain high-quality spectra of stars in the ultraviolet, optical and infrared wavelength regions on a routine basis. The interpretation of these spectra is often based on synthetic stellar spectra, either calculated on the fly or taken from a spectral library. One of the most important ingredients of these spectra is a set of high-quality 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 and improve the relevant experimental and theoretical atomic data. As an example, we briefly describe the efforts done in the context of the Gaia-ESO Public Spectroscopic Survey to compile and assess the best available data in a standard way, providing a list of recommended lines for analysis of optical spectra of FGK stars. The line data, together with specialised analysis methods, allow different surveys to obtain abundances with typical precisions of ∼0.1 dex on an industrial scale for ∼10 chemical elements. Several elements with urgent need for better atomic data have been identified.

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The galactic habitable zone in elliptical galaxies

International Journal of Astrobiology ◽

10.1017/s1473550412000055 ◽

2012 ◽

Vol 11 (3) ◽

pp. 157-161 ◽

Cited By ~ 12

Author(s):

Falguni Suthar ◽

Christopher P. McKay

Keyword(s):

Milky Way ◽

Planet Formation ◽

Elliptical Galaxies ◽

Extrasolar Planet ◽

Habitable Zone ◽

Milky Way Galaxy ◽

Habitable Zones ◽

Nearby Stars ◽

Host Stars ◽

Metallicity Distribution

AbstractThe concept of a Galactic Habitable Zone (GHZ) was introduced for the Milky Way galaxy a decade ago as an extension of the earlier concept of the Circumstellar Habitable Zone. In this work, we consider the extension of the concept of a GHZ to other types of galaxies by considering two elliptical galaxies as examples, M87 and M32. We argue that the defining feature of the GHZ is the probability of planet formation which has been assumed to depend on the metallicity. We have compared the metallicity distribution of nearby stars with the metallicity of stars with planets to document the correlation between metallicity and planet formation and to provide a comparison to other galaxies. Metallicity distribution, based on the [Fe/H] ratio to solar, of nearby stars peaks at [Fe/H]≈−0.2 dex, whereas the metallicity distribution of extrasolar planet host stars peaks at [Fe/H]≈+0.4 dex. We compare the metallicity distribution of extrasolar planet host stars with the metallicity distribution of the outer star clusters of M87 and M32. The metallicity distribution of stars in the outer regions of M87 peaks at [Fe/H]≈−0.2 dex and extends to [Fe/H]≈+0.4 dex, which seems favourable for planet formation. The metallicity distribution of stars in the outer regions of M32 peaks at [Fe/H]≈−0.2 dex and extends to a much lower [Fe/H]. Both elliptical galaxies met the criteria of a GHZ. In general, many galaxies should support habitable zones.

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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.

Canadian Journal of Physics ◽

10.1139/p10-119 ◽

2011 ◽

Vol 89 (4) ◽

pp. 327-331 ◽

Cited By ~ 5

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.

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Extrasolar Planets and Prospects for Terrestrial Planets

Symposium - International Astronomical Union ◽

10.1017/s0074180900192903 ◽

2004 ◽

Vol 213 ◽

pp. 11-24 ◽

Cited By ~ 1

Author(s):

Geoffrey W. Marcy ◽

R. Paul Butler ◽

Steven S. Vogt ◽

Debra A. Fischer

Keyword(s):

Solar System ◽

Milky Way ◽

Extrasolar Planets ◽

Terrestrial Planets ◽

Habitable Zone ◽

Milky Way Galaxy ◽

System Architectures ◽

Rocky Planets ◽

Host Stars ◽

Eccentricity Orbit

Examination of ∼2000 sun–like stars has revealed 97 planets (as of 2002 Nov), all residing within our Milky Way Galaxy and within ∼200 light years of our Solar System. They have masses between 0.1 and 10 times that of Jupiter, and orbital sizes of 0.05–5 AU. Thus planets occupy the entire detectable domain of mass and orbits. News & summaries about extrasolar planets are provided at: http://exoplanets.org. These planets were all discovered by the wobble of the host stars, induced gravitationally by the planets, causing a periodicity in the measured Doppler effect of the starlight. Earth–mass planets remain undetectable, but space–based missions such as Kepler, COROT and SIM may provide detections of terrestrial planets within the next decade.The number of planets increases with decreasing planet mass, indicating that nature makes more small planets than jupiter–mass planets. Extrapolation, though speculative, bodes well for an even larger number of earth–mass planets. These observations and the theory of planet formation suggests that single sun–like stars commonly harbor earth–sized rocky planets, as yet undetectable. The number of planets increases with increasing orbital distance from the host star, and most known planets reside in non–circular orbits. Many known planets reside in the habitable zone (albeit being gas giants) and most newly discovered planets orbit beyond 1 AU from their star. A population of Jupiter–like planets may reside at 5–10 AU from stars, not easily detectable at present. The sunlike star 55 Cancri harbors a planet of 4–10 Jupiter masses orbiting at 5.5 AU in a low eccentricity orbit, the first analog of our Jupiter, albeit with two large planets orbiting inward.To date, 10 multiple–planet systems have been discovered, with four revealing gravitational interactions between the planets in the form of resonances. GJ 876 has two planets with periods of 1 and 2 months. Other planetary systems are “hierarchical”, consisting of widely separated orbits. These two system architectures probably result from gravitational interactions among the planets and between the planets and the proto-planetary disk out of which they formed.

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

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833553 ◽

2019 ◽

Vol 624 ◽

pp. A60 ◽

Cited By ~ 4

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.

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VALD: The Meeting Point of Data Producers and Data Users

10.20944/preprints201806.0422.v1 ◽

2018 ◽

Author(s):

Tatiana Ryabchikova ◽

Yury Pakhomov ◽

Nikolai Piskunov

Keyword(s):

Data Model ◽

Spectral Synthesis ◽

Energy Levels ◽

Critical Evaluation ◽

Spectral Lines ◽

Atomic Data ◽

Spectra Analysis ◽

Stellar Spectra ◽

Data Content ◽

Hyperfine Structures

Vienna Atomic Line Database (VALD) contains data on atomic and molecular energy levels and parameters of spectral lines required for stellar spectra analysis. Hundreds of millions lines for fine spectral synthesis and for opacity calculations are collected in present version of VALD (VALD3). Critical evaluation of the data and the diversity of extraction tools support high popularity of VALD among users. The data model of VALD3 incorporates obligatory links to the bibliography making our database more attractive as publishing platform for data producers. The VALD data quality and completeness are constantly improving allowing better reproduction of stellar spectra. To illustrate continuous evolution of the data content we present a comparative analysis of the recent experimental and theoretical atomic data for Fe-group elements, which will be included in the next VALD release. This release will also include a possibility for extracting the line data with full isotopic and hyperfine structures.

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

Astronomy and Astrophysics ◽

10.1051/0004-6361/201731933 ◽

2018 ◽

Vol 612 ◽

pp. A60 ◽

Cited By ~ 9

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.

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The Laboratory Astrophysics Spectroscopy Programme at Imperial College London

Galaxies ◽

10.3390/galaxies6040109 ◽

2018 ◽

Vol 6 (4) ◽

pp. 109 ◽

Cited By ~ 1

Author(s):

María Belmonte ◽

Juliet Pickering ◽

Christian Clear ◽

Florence Concepción Mairey ◽

Florence Liggins

Keyword(s):

Vacuum Ultraviolet ◽

Transition Probabilities ◽

Energy Levels ◽

Visible Region ◽

Infrared Region ◽

Imperial College ◽

Laboratory Astrophysics ◽

Atomic Data ◽

Full Potential ◽

Stellar Spectra

Accurate atomic parameters, such as transition probabilities, wavelengths, and energy levels, are indispensable for the analysis of stellar spectra and the obtainment of chemical abundances. However, the quantity and quality of the existing data in many cases lie far from the current needs of astronomers, creating an acute need for laboratory measurements of matching accuracy and completeness to exploit the full potential of the very expensively acquired astrophysical spectra. The Fourier Transform Spectrometer at Imperial College London works in the vacuum ultraviolet-visible region with a resolution of 2,000,000 at 200 nm. We can acquire calibrated spectra of neutral, singly, and doubly ionized species. We collaborate with the National Institute of Standards and Technology (NIST) and the University of Lund to extend our measurements into the infrared region. The aim of this review is to explain the current capabilities of our experiment in an understandable way to bring the astronomy community closer to the field of laboratory astrophysics and encourage further dialogue between our laboratory and all those astronomers who need accurate atomic data. This exchange of ideas will help us to focus our efforts on the most urgently needed data.

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The Long View of Planetary Systems

10.1093/oso/9780198799894.003.0011 ◽

2018 ◽

Author(s):

Karel Schrijver

Keyword(s):

Solar System ◽

Milky Way ◽

Planetary Systems ◽

Giant Planets ◽

Milky Way Galaxy ◽

Population Statistics ◽

The Past ◽

General Terms ◽

The Galaxy ◽

The Universe

How many planetary systems formed before our’s did, and how many will form after? How old is the average exoplanet in the Galaxy? When did the earliest planets start forming? How different are the ages of terrestrial and giant planets? And, ultimately, what will the fate be of our Solar System, of the Milky Way Galaxy, and of the Universe around us? We cannot know the fate of individual exoplanets with great certainty, but based on population statistics this chapter sketches the past, present, and future of exoworlds and of our Earth in general terms.

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A Statistical Estimation of the Occurrence of Extraterrestrial Intelligence in the Milky Way Galaxy

Galaxies ◽

10.3390/galaxies9010005 ◽

2021 ◽

Vol 9 (1) ◽

pp. 5

Author(s):

Xiang Cai ◽

Jonathan H. Jiang ◽

Kristen A. Fahy ◽

Yuk L. Yung

Keyword(s):

Statistical Estimation ◽

Milky Way ◽

Galactic Center ◽

Model Simulation ◽

Temporal Variations ◽

Extraterrestrial Intelligence ◽

Milky Way Galaxy ◽

The Galaxy ◽

Peak Location ◽

Intelligent Life

In the field of astrobiology, the precise location, prevalence, and age of potential extraterrestrial intelligence (ETI) have not been explicitly explored. Here, we address these inquiries using an empirical galactic simulation model to analyze the spatial–temporal variations and the prevalence of potential ETI within the Galaxy. This model estimates the occurrence of ETI, providing guidance on where to look for intelligent life in the Search for ETI (SETI) with a set of criteria, including well-established astrophysical properties of the Milky Way. Further, typically overlooked factors such as the process of abiogenesis, different evolutionary timescales, and potential self-annihilation are incorporated to explore the growth propensity of ETI. We examine three major parameters: (1) the likelihood rate of abiogenesis (λA); (2) evolutionary timescales (Tevo); and (3) probability of self-annihilation of complex life (Pann). We found Pann to be the most influential parameter determining the quantity and age of galactic intelligent life. Our model simulation also identified a peak location for ETI at an annular region approximately 4 kpc from the galactic center around 8 billion years (Gyrs), with complex life decreasing temporally and spatially from the peak point, asserting a high likelihood of intelligent life in the galactic inner disk. The simulated age distributions also suggest that most of the intelligent life in our galaxy are young, thus making observation or detection difficult.

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