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- Cescutti, G., et al.
(author)
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MINCE I. Presentation of the project and of the first year sample
- 2022
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 668
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Journal article (peer-reviewed)abstract
- Context. In recent years, Galactic archaeology has become a particularly vibrant field of astronomy, with its main focus set on the oldest stars of our Galaxy. In most cases, these stars have been identified as the most metal-poor. However, the struggle to find these ancient fossils has produced an important bias in the observations - in particular, the intermediate metal-poor stars (-2.5 < [Fe/H] < -1.5) have been frequently overlooked. The missing information has consequences for the precise study of the chemical enrichment of our Galaxy, in particular for what concerns neutron capture elements and it will be only partially covered by future multi object spectroscopic surveys such as WEAVE and 4MOST.Aims. Measuring at Intermediate Metallicity Neutron Capture Elements (MINCE) is gathering the first high-quality spectra (high signal-to-noise ratio, S/N, and high resolution) for several hundreds of bright and metal-poor stars, mainly located in our Galactic halo.Methods. We compiled our selection mainly on the basis of Gaia data and determined the stellar atmospheres of our sample and the chemical abundances of each star.Results. In this paper, we present the first sample of 59 spectra of 46 stars. We measured the radial velocities and computed the Galactic orbits for all stars. We found that 8 stars belong to the thin disc, 15 to disrupted satellites, and the remaining cannot be associated to the mentioned structures, and we call them halo stars. For 33 of these stars, we provide abundances for the elements up to zinc. We also show the chemical evolution results for eleven chemical elements, based on recent models.Conclusions. Our observational strategy of using multiple telescopes and spectrographs to acquire high S/N and high-resolution spectra for intermediate-metallicity stars has proven to be very efficient, since the present sample was acquired over only about one year of observations. Finally, our target selection strategy, after an initial adjustment, proved satisfactory for our purposes.
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| 2. |
- Deshmukh, S. A., et al.
(author)
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The solar photospheric silicon abundance according to (COBOLD)-B-5 : Investigating line broadening, magnetic fields, and model effects
- 2022
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 668
-
Journal article (peer-reviewed)abstract
- Context. In this work, we present a photospheric solar silicon abundance derived using (COBOLD)-B-5 model atmospheres and the LINFOR3D spectral synthesis code. Previous works have differed in their choice of a spectral line sample and model atmosphere as well as their treatment of observational material, and the solar silicon abundance has undergone a downward revision in recent years. We additionally show the effects of the chosen line sample, broadening due to velocity fields, collisional broadening, model spatial resolution, and magnetic fields. Aims. Our main aim is to derive the photospheric solar silicon abundance using updated oscillator strengths and to mitigate model shortcomings such as over-broadening of synthetic spectra. We also aim to investigate the effects of different line samples, fitting configurations, and magnetic fields on the fitted abundance and broadening values. Methods. (COBOLD)-B-5 model atmospheres for the Sun were used in conjunction with the LINFOR3D spectral synthesis code to generate model spectra, which were then fit to observations in the Hamburg solar atlas. We took pixel-to-pixel signal correlations into account by means of a correlated noise model. The choice of line sample is crucial to determining abundances, and we present a sample of 11 carefully selected lines (from an initial choice of 39 lines) in both the optical and infrared, which has been made possible with newly determined oscillator strengths for the majority of these lines. Our final sample includes seven optical Si I lines, three infrared Si I lines, and one optical Si II line. Results. We derived a photospheric solar silicon abundance of log epsilon(Si) = 7.57 +/- 0.04, including a -0.01 dex correction from Non-Local Thermodynamic Equilibrium (NLTE) effects. Combining this with meteoritic abundances and previously determined photospheric abundances results in a metal mass fraction Z/X = 0.0220 +/- 0.0020. We found a tendency of obtaining overly broad synthetic lines. We mitigated the impact of this by devising a de-broadening procedure. The over-broadening of synthetic lines does not substantially affect the abundance determined in the end. It is primarily the line selection that affects the final fitted abundance.
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| 3. |
- Kucinskas, A., et al.
(author)
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Magnitude And Color Transformations Between Sirius And 2Mass Photometric Systems
- 2008
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In: Baltic Astronomy. - 1392-0049. ; 17:3-4, s. 283-292
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Journal article (peer-reviewed)abstract
- We provide magnitude and color transformations between two near-infrared photometric systems, 2MASS and SIRIUS, the latter currently implemented with the three-Channel SIRIUS camera on 1.4 m Infrared Survey Facility telescope at the South African Astronomical Observatory. The transformation equations are derived using a carefully selected sample of 32 770 stars in the. Large and Small Magellanic Clouds that have high quality observations available in both photometric systems. The derived transformations are valid in the color range -0.1 < (J - H)(SIRIUS) < 1.15, -0.05 < (H - K-s)(SIRIUS) < 0.7 and -0.1 < (J - K-s)(SIRIUS) < 1.7.
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