| 1. |
- Heiter, Ulrike, et al.
(författare)
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Atomic and molecular data for optical stellar spectroscopy
- 2015
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Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 90:5
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Tidskriftsartikel (refereegranskat)abstract
- High-precision spectroscopy of large stellar samples plays a crucial role for several topical issues in astrophysics. Examples include studying the chemical structure and evolution of the Milky Way Galaxy, tracing the origin of chemical elements, and characterizing planetary host stars. Data are accumulating from instruments that obtain high-quality spectra of stars in the ultraviolet, optical and infrared wavelength regions on a routine basis. These instruments are located at ground-based 2-10 m class telescopes around the world, in addition to the spectrographs with unique capabilities available at the Hubble Space Telescope. The interpretation of these spectra requires high-quality transition data for numerous species, in particular neutral and singly ionized atoms, and di-or triatomic molecules. We rely heavily on the continuous efforts of laboratory astrophysics groups that produce and improve the relevant experimental and theoretical atomic and molecular data. The compilation of the best available data is facilitated by databases and electronic infrastructures such as the NIST Atomic Spectra Database, the VALD database, or the Virtual Atomic and Molecular Data Centre. We illustrate the current status of atomic data for optical stellar spectra with the example of the Gaia-ESO Public Spectroscopic Survey. Data sources for 35 chemical elements were reviewed in an effort to construct a line list for a homogeneous abundance analysis of up to 10(5) stars.
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| 2. |
- Belmonte, M. T., et al.
(författare)
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Fe I Oscillator Strengths for Transitions from High-lying Odd-parity Levels
- 2017
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Ingår i: Astrophysical Journal. - : IOP PUBLISHING LTD. - 0004-637X .- 1538-4357. ; 848:2
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Tidskriftsartikel (refereegranskat)abstract
- We report new experimental Fe I oscillator strengths obtained by combining measurements of branching fractions measured with a Fourier Transform spectrometer and time-resolved, laser-induced fluorescence lifetimes. This study covers the spectral region ranging from 213 to 1033 nm. A total of 120 experimental log(gf)-values coming from 15 odd-parity energy levels are provided, 22 of which have not been reported previously and 63 of which have values with lower uncertainty than the existing data. The radiative lifetimes for 60 upper energy levels are presented, 39 of which have no previous measurements.
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| 3. |
- Den Hartog, E. A., et al.
(författare)
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Fe I oscillator strengths for transitions from high-lying even-parity levels
- 2014
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Ingår i: Astrophysical Journal Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 215:2, s. 23-
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Tidskriftsartikel (refereegranskat)abstract
- New radiative lifetimes, measured to +or-5% accuracy, are reported for 31 even-parity levels of Fe I ranging from 45061 cm -1 to 56842 cm -1. These lifetimes have been measured using single-step and two-step time-resolved laser-induced fluorescence on a slow atomic beam of iron atoms. Branching fractions have been attempted for all of these levels, and completed for 20 levels. This set of levels represents an extension of the collaborative work reported in Ruffoni et al. The radiative lifetimes combined with the branching fractions yields new oscillator strengths for 203 lines of Fe I. Utilizing a 1D-LTE model of the solar photosphere, spectral syntheses for a subset of these lines which are unblended in the solar spectrum yields a mean iron abundance of langlog[epsilon(Fe)]rang = 7.45 +or- 0.06.
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| 4. |
- Pickering, J. C., et al.
(författare)
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Laboratory measurements of oscillator strengths and their astrophysical applications
- 2011
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Ingår i: Canadian Journal of Physics. - 0008-4204. ; 89:4, s. 387-393
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Forskningsöversikt (refereegranskat)abstract
- We present an overview of current needs for accurate laboratory atomic transition probabilities (log(gf)) for astrophysical applications, particularly for iron group element spectra in the IR, optical, UV, and VUV spectral regions. Examples are given of our recent measurements, undertaken using the combination of high-resolution Fourier transform spectrometry and time-resolved laser-induced fluorescence. Laboratory measured log(gf) values are particularly important for the determination of elemental abundances in astrophysical objects. Advances in astronomical instrumentation, particularly access to underexplored regions (IR, vacuum UV, VUV), require improved accuracy and completeness of the atomic database for meaningful analyses of astrophysical spectra.
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