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  • 1.
    Jönsson, Henrik
    et al.
    Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University, Box 43, 221 00 Lund, Sweden; Instituto de Astrofísica de Canarias (IAC), 38205 La Laguna, Tenerife, Spain; Universidad de La Laguna, Dpto. Astrofísica, 38206 La Laguna, Tenerife, Spain.
    Ryde, Nils
    Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University, Box 43, 221 00 Lund, Sweden.
    Nordlander, T
    Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden.
    Pehlivan Rhodin, Asli
    Malmö högskola, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM). Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University, Box 43, 221 00 Lund, Sweden.
    Hartman, Henrik
    Malmö högskola, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM). Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University, Box 43, 221 00 Lund, Sweden.
    Jönsson, Per
    Malmö högskola, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM).
    Eriksson, Kjell
    Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden.
    Abundances of disk and bulge giants from high-resolution optical spectra: I. O, Mg, Ca, and Ti in the solar neighborhood and Kepler field samples2017In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 598, article id A100Article in journal (Refereed)
    Abstract [en]

    Context. The Galactic bulge is an intriguing and significant part of our Galaxy, but it is hard to observe because it is both distant and covered by dust in the disk. Therefore, there are not many high-resolution optical spectra of bulge stars with large wavelength coverage, whose determined abundances can be compared with nearby, similarly analyzed stellar samples. Aims. We aim to determine the diagnostically important alpha elements of a sample of bulge giants using high-resolution optical spectra with large wavelength coverage. The abundances found are compared to similarly derived abundances from similar spectra of similar stars in the local thin and thick disks. In this first paper we focus on the solar neighborhood reference sample. Methods. We used spectral synthesis to derive the stellar parameters as well as the elemental abundances of both the local and bulge samples of giants. We took special care to benchmark our method of determining stellar parameters against independent measurements of effective temperatures from angular diameter measurements and surface gravities from asteroseismology. Results. In this first paper we present the method used to determine the stellar parameters and elemental abundances, evaluate them, and present the results for our local disk sample of 291 giants. Conclusions. When comparing our determined spectroscopic temperatures to those derived from angular diameter measurements, we reproduce these with a systematic difference of +10 K and a standard deviation of 53 K. The spectroscopic gravities reproduce those determined from asteroseismology with a systematic offset of +0.10 dex and a standard deviation of 0.12 dex. When it comes to the abundance trends, our sample of local disk giants closely follows trends found in other works analyzing solar neighborhood dwarfs, showing that the much brighter giant stars are as good abundance probes as the often used dwarfs.

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  • 2.
    Pehlivan, Asli
    et al.
    Malmö högskola, Faculty of Technology and Society (TS). Lund Observatory, Box 43, 221 00 Lund, Sweden.
    Nilsson, Hampus
    Lund Observatory, Box 43, 221 00 Lund, Sweden.
    Hartman, Henrik
    Malmö högskola, Faculty of Technology and Society (TS). Lund Observatory, Box 43, 221 00 Lund, Sweden.
    Laboratory oscillator strengths of Sc i in the near-infrared region for astrophysical applications2015In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 582, no A98, article id A98Article in journal (Refereed)
    Abstract [en]

    Context. Atomic data is crucial for astrophysical investigations. To understand the formation and evolution of stars, we need to analyse their observed spectra. Analysing a spectrum of a star requires information about the properties of atomic lines, such as wavelengths and oscillator strengths. However, atomic data of some elements are scarce, particularly in the infrared region, and this paper is part of an effort to improve the situation on near-IR atomic data. Aims. This paper investigates the spectrum of neutral scandium, Sc i, from laboratory measurements and improves the atomic data of Sc i lines in the infrared region covering lines in R, I, J, and K bands. Especially, we focus on measuring oscillator strengths for Sc i lines connecting the levels with 4p and 4s configurations. Methods. We combined experimental branching fractions with radiative lifetimes from the literature to derive oscillator strengths (f -values). Intensity-calibrated spectra with high spectral resolution were recorded with Fourier transform spectrometer from a hollow cathode discharge lamp. The spectra were used to derive accurate oscillator strengths and wavelengths for Sc i lines, with emphasis on the infrared region. Results. This project provides the first set of experimental Sc i lines in the near-infrared region for accurate spectral analysis of astronomical objects. We derived 63 log(g f ) values for the lines between 5300 Å and 24 300 Å. The uncertainties in the f -values vary from 5% to 20%. The small uncertainties in our values allow for an increased accuracy in astrophysical abundance determinations

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  • 3.
    Pehlivan Rhodin, Asli
    et al.
    Malmö högskola, Faculty of Technology and Society (TS). Lund Observatory, Lund University, PO Box 43, SE-221 00 Lund, Sweden.
    Belmonte, Teruca
    Physics Department, Blackett Laboratory, Imperial College London, London SW7 2BZ, UK.
    Engström, Lars
    Department of Physics, Lund Institute of Technology, PO Box 118, SE-221 00 Lund, Sweden.
    Lundberg, Hans
    Department of Physics, Lund Institute of Technology, PO Box 118, SE-221 00 Lund, Sweden.
    Nilsson, Hampus
    Lund Observatory, Lund University, PO Box 43, SE-221 00 Lund, Sweden.
    Hartman, Henrik
    Malmö högskola, Faculty of Technology and Society (TS). Lund Observatory, Lund University, PO Box 43, SE-221 00 Lund, Sweden.
    Pickering, Juliet
    Physics Department, Blackett Laboratory, Imperial College London, London SW7 2BZ, UK.
    Clear, Christian
    Physics Department, Blackett Laboratory, Imperial College London, London SW7 2BZ, UK.
    Quinet, Pascal
    Physique Atomique et Astrophysique, Université de Mons–UMONS, 20 Place du Parc, B-7000 Mons, Belgium; IPNAS, Université de Liège, B15 Sart Tilman, B-4000 Liège, Belgium.
    Fivet, Vanessa
    Physique Atomique et Astrophysique, Université de Mons–UMONS, 20 Place du Parc, B-7000 Mons, Belgium.
    Palmeri, Patrick
    Physique Atomique et Astrophysique, Université de Mons–UMONS, 20 Place du Parc, B-7000 Mons, Belgium.
    Lifetime measurements and oscillator strengths insingly ionized scandium and the solar abundance of scandium2017In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 472, no 3, p. 3337-3353Article in journal (Refereed)
    Abstract [en]

    The lifetimes of 17 even-parity levels (3d5s, 3d4d, 3d6s, and 4p$^2$) in the region 57743-77837 cm$^{-1}$ of singly ionised scandium (\ion{Sc}{ii}) were measured by two-step time-resolved laser induced fluorescence spectroscopy. Oscillator strengths of 57 lines from these highly excited upper levels were derived using a hollow cathode discharge lamp and a Fourier transform spectrometer. In addition, Hartree--Fock calculations where both the main relativistic and core-polarisation effects were taken into account were carried out for both low- and high-excitation levels. There is a good agreement for most of the lines between our calculated branching fractions and the measurements of Lawler and Dakin (1989) in the region 9000-45000 cm$^{-1}$ for low excitation levels and with our measurements for high excitation levels in the region 23500-63100 cm$^{-1}$. This, in turn, allowed us to combine the calculated branching fractions with the available experimental lifetimes to determine semi-empirical oscillator strengths for a set of 380 E1 transitions in \ion{Sc}{ii}. These oscillator strengths include the weak lines that were used previously to derive the solar abundance of scandium. The solar abundance of scandium is now estimated to $\log~\epsilon_\odot = 3.04\pm0.13$ using these semi-empirical oscillator strengths to shift the values determined by Scott et al. (2015). The new estimated abundance value is in agreement with the meteoritic value ($\log~\epsilon_{\text{met}}=3.05\pm0.02$) of Lodders et al. (2009).

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  • 4.
    Pehlivan Rhodin, Asli
    et al.
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM). Lund Univ, Dept Phys, Div Astrophys, SE-221 00 Lund, Sweden..
    Hartman, Henrik
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM).
    Nilsson, Hampus
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM).
    Jönsson, Per
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM).
    Accurate and experimentally validated transition data for Si I and Si II2024In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 682, article id A184Article in journal (Refereed)
    Abstract [en]

    Aims. The aim of this study is to provide radiative data for neutral and singly ionised silicon, in particular for the first experimental oscillator strengths for near-infrared Si I lines. In addition, we aim to perform atomic structure calculations both for neutral and singly ionised silicon while including lines from highly excited levels.

    Methods. We performed large-scale atomic structure calculations with the relativistic multiconfiguration Dirac-Hartree-Fock method using the GRASP2K package to determine log(𝑔ƒ) values of Si I and Si II lines, taking into account valence-valence and core-valence electron correlation. In addition, we derived oscillator strengths of near-infrared Si I lines by combining the experimental branching fractions with radiative lifetimes from our calculations. The silicon plasma was obtained from a hollow cathode discharge lamp, and the intensity-calibrated high-resolution spectra between 1037 and 2655 nm were recorded by a Fourier transform spectrometer.

    Results. We provide an extensive set of accurate experimental and theoretical log(𝑔ƒ) values. For the first time, we derived 17 log(𝑔ƒ) values of Si I lines in the infrared from experimental measurements. We report data for 1500 Si I lines and 500 Si II lines. The experimental uncertainties of our ƒ-values vary between 5% for the strong lines and 25% for the weak lines. The theoretical log(𝑔ƒ) values for Si I lines in the range 161 nm to 6340 nm agree very well with the experimental values of this study and complete the missing transitions involving levels up to 3s23p7s (61 970 cm−1). In addition, we provide accurate calculated log(𝑔ƒ) values of Si II lines from the levels up to 3s27f (122 483 cm−1) in the range 81 nm to 7324 nm.

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  • 5.
    Pehlivan-Rhodin, Asli
    et al.
    Malmö högskola, Faculty of Technology and Society (TS). Lund Observatory, PO Box 43, 221 00 Lund, Sweden.
    Hartman, Henrik
    Malmö högskola, Faculty of Technology and Society (TS). Lund Observatory, PO Box 43, 221 00 Lund, Sweden.
    Nilsson, Hampus
    Lund Observatory, PO Box 43, 221 00 Lund, Sweden.
    Jönsson, Per
    Malmö högskola, Faculty of Technology and Society (TS).
    Experimental and theoretical oscillator strengths of Mg i for accurate abundance analysis2017In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 598, no A102, article id A102Article in journal (Refereed)
    Abstract [en]

    Context. With the aid of stellar abundance analysis, it is possible to study the galactic formation and evolution. Magnesium is an important element to trace the -element evolution in our Galaxy. For chemical abundance analysis, such as magnesium abundance, accurate and complete atomic data are essential. Inaccurate atomic data lead to uncertain abundances and prevent discrimination between di erent evolution models. Aims.We study the spectrum of neutral magnesium from laboratory measurements and theoretical calculations. Our aim is to improve the oscillator strengths ( f -values) of Mgi lines and to create a complete set of accurate atomic data, particularly for the near-IR region. Methods. We derived oscillator strengths by combining the experimental branching fractions with radiative lifetimes reported in the literature and computed in this work. A hollow cathode discharge lamp was used to produce free atoms in the plasma and a Fourier transform spectrometer recorded the intensity-calibrated high-resolution spectra. In addition, we performed theoretical calculations using the multiconfiguration Hartree-Fock program ATSP2K. Results. This project provides a set of experimental and theoretical oscillator strengths. We derived 34 experimental oscillator strengths. Except from the Mgi optical triplet lines (3p 3Po0;1;2 - 4s 3S1), these oscillator strengths are measured for the first time. The theoretical oscillator strengths are in very good agreement with the experimental data and complement the missing transitions of the experimental data up to n = 7 from even and odd parity terms. We present an evaluated set of oscillator strengths, gf, with uncertainties as small as 5%. The new values of the Mgi optical triplet line (3p 3Po0 ;1;2 - 4s 3S1) oscillator strength values are 0.08 dex larger than the previous measurements.

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1 - 5 of 5
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