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Photospheric C, N, and O abundances of 118 solar-analog stars were determined by applying the synthetic-fitting analysis to their spectra in the blue or near-UV region comprising lines of CH, NH, and OH molecules, with an aim of clarifying…

Solar and Stellar Astrophysics · Physics 2023-02-01 Yoichi Takeda

We have compiled a large catalogue of metallicities and abundance ratios from the literature in order to investigate abundance trends of several alpha and iron peak elements in the thin disk and the thick disk of the Galaxy. The catalogue…

Astrophysics · Physics 2009-11-10 C. Soubiran , P. Girard

We investigate sulphur abundance in 74 Galactic stars by using high resolution spectra obtained at ESO VLT and NTT telescopes. For the first time the abundances are derived, where possible, from three optical multiplets: Mult. 1, 6, and 8.…

Astrophysics · Physics 2009-11-11 E. Caffau , P. Bonifacio , R. Faraggiana , P. Francois , R. G. Gratton , M. Barbieri

Precise abundance ratios are determined for 94 dwarf stars with 5200 < Teff < 6300 K, -1.6 < [Fe/H] < -0.4, and distances D < 335 pc. Most of them have halo kinematics, but 16 thick-disk stars are included. Equivalent widths of atomic lines…

Astrophysics of Galaxies · Physics 2015-05-18 Poul E. Nissen , William J. Schuster

We report detailed analysis of high-resolution spectra of nine high velocity metal-rich dwarfs in the solar neighborhood. The stars are super metal-rich and 5 of them have [Fe/H]>=+0.4, making them the most metal-rich stars currently known.…

Astrophysics · Physics 2009-10-30 S. Castro , R. M. Rich , M. Grenon , B. Barbuy , J. K. McCarthy

We present the results of our investigation of three samples kinematically representative of the thin and thick disks and the Hercules stream using the catalogue of Soubiran & Girard (2005). We have observed abundance trends and age…

Astrophysics · Physics 2009-07-10 Pascal Girard , Caroline Soubiran

We describe a method for the determination of stellar [C/Fe] abundance ratios using low-resolution (R = 2000) stellar spectra from the SDSS and SEGUE. By means of a star-by-star comparison with a set of SDSS/SEGUE spectra with available…

A previous study of correlations between element abundance ratios, [X/Fe], and ages of solar twin stars is extended to include Sc, Mn, Cu, and Ba. HARPS spectra with S/N > 600 are used to derive very precise (+/- 0.01 dex) differential…

Solar and Stellar Astrophysics · Physics 2016-09-21 P. E. Nissen

Carbon and oxygen abundances in F and G main-sequence stars ranging in metallicity from [Fe/H] = -1.6 to +0.5 are determined from a non-LTE analysis of CI and OI atomic lines in high-resolution spectra. Both C and O are good tracers of…

Astrophysics of Galaxies · Physics 2015-06-16 Poul E. Nissen , William J. Schuster

Many nucleosynthetic channels create the elements, but two-parameter models characterized by $\alpha$ and Fe nonetheless predict stellar abundances in the Galactic disk to accuracies of 0.02 to 0.05 dex for most measured elements, near the…

High-resolution, high-signal-to-noise (<S/N> = 85) spectra have been obtained for five stars -- CD-24:17504, CD-38:245, CS 22172-002, CS 22885-096, and CS 22949-037 -- having [Fe/H] < -3.5 according to previous lower S/N material. LTE…

Astrophysics · Physics 2009-11-06 John E. Norris , Sean G. Ryan , Timothy C. Beers

A previous study (Nissen & Schuster 2010) of 94 dwarf stars with -1.6 < [Fe/H] < -0.4 has revealed the existence of two distinct halo populations with a systematic difference in [alpha/Fe] at a given metallicity. In continuation of that…

Astrophysics of Galaxies · Physics 2015-05-27 Poul E. Nissen , William J. Schuster

The measurement of the structure of stellar populations in the Milky Way disk places fundamental constraints on models of galaxy formation and evolution. Previously, the disk's structure has been studied in terms of populations defined…

Exploring the Galactic chemical evolution and enrichment scenarios with open clusters allows us to understand the history of the Milky Way disk. High-resolution spectra of OCs are a crucial tool, as they provide precise chemical…

Solar twins are stars with similar stellar (surface) parameters to the Sun that can have a wide range of ages. This provide an opportunity to analyze the variation of their chemical abundances with age. Nissen (2015) recently suggested that…

Solar and Stellar Astrophysics · Physics 2016-05-04 M. Tucci Maia , I. Ramírez , J. Meléndez , M. Bedell , J. L. Bean , M. Asplund

We present new stellar population models, $\alpha$-MC, self-consistently taking into account non-solar $\rm [\alpha/Fe]$ abundances for both isochrones and stellar spectra. The $\alpha$-MC models are based on $\alpha$-enhanced MIST…

Astrophysics of Galaxies · Physics 2024-10-30 Minjung Park , Charlie Conroy , Benjamin D. Johnson , Joel Leja , Aaron Dotter , Phillip A. Cargile

We present a new calibration of the seven-color Vilnius system in terms of [Fe/H], applicable to F-M stars in the metallicity range -2.8<[Fe/H]<+0.5. We employ a purely empirical approach, based on ~1000 calibrating stars with…

Instrumentation and Methods for Astrophysics · Physics 2018-03-14 S. Bartasiute , S. Raudeliunas , J. Sperauskas

The radial profiles of the Hb, Mg, and Fe line-strength indices are presented for a sample of eight spiral galaxies with a low surface-brightness stellar disc and a bulge. The correlations between the central values of the line-strength…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-04 L. Morelli , E. M. Corsini , A. Pizzella , E. Dalla Bontà , L. Coccato , J. Méndez-Abreu , M. Cesetti

We present new, high-to-intermediate spectral resolution stellar population models, based on four popular libraries of empirical stellar spectra, namely Pickles, ELODIE, STELIB and MILES. These new models are the same as our previous…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-30 Claudia Maraston , Gustav Stromback , ICG-University of Portsmouth , United Kingdom

We determined the atmospheric parameters and abundance pattern for a sample of metal-rich barium stars. We used high-resolution optical spectroscopy. Atmospheric parameters and abundances were determined using the local thermodynamic…

Solar and Stellar Astrophysics · Physics 2011-08-12 C. B. Pereira , J. V. Sales Silva , C. Chavero , F. Roig , E. Jilinski