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Abundance anomalies have been determined at the surface of many field and open cluster A and F dwarfs. These abundance anomalies are most likely caused by microscopic diffusion at work within the stable envelopes of A stars. However…

Solar and Stellar Astrophysics · Physics 2010-11-10 M. Gebran , R. Monier

Detailed chemical abundances of Galactic stars are needed in order to improve our knowledge of the formation and evolution of our galaxy, the Milky Way. We took advantage of the GIANO archive spectra to select a sample of Galactic disc…

Solar and Stellar Astrophysics · Physics 2019-01-30 E. Caffau , P. Bonifacio , E. Oliva , S. Korotin , L. Capitanio , S. Andrievsky , R. Collet , L. Sbordone , S. Duffau , N. Sanna , L. Origlia , N. Ryde , H. -G. Ludwig

We determined the silicon abundances of 253 metal-poor stars in the metallicity range $-4<\mathrm{[Fe/H]} <-1.5$, based on non-local thermodynamic equilibrium (NLTE) line formation calculations of neutral silicon and high-resolution spectra…

Solar and Stellar Astrophysics · Physics 2015-05-19 L. Zhang , T. Karlsson , N. Christlieb , A. J. Korn , P. S. Barklem , G. Zhao

We present results of a detailed chemical analysis performed on 23 main-sequence turnoff stars having -3.4<=[Fe/H]<=-2.2, a sample selected to be highly homogeneous in T_eff and log(g). We investigate the efficiency of mixing in the early…

Astrophysics · Physics 2009-11-10 E. Arnone , S. G. Ryan , D. Argast , J. E. Norris , T. C. Beers

LTE and NLTE abundances of sulfur in 6 metal-poor giants and 61 dwarfs (62 dwarfs, including the Sun) were explored in the range of -3 \lsim [Fe/H] \lsim $+0.5$ using high-resolution, high signal-to-noise ratio spectra of the \SI 8693.9 \AA…

We report a detailed spectroscopic abundance analysis for a sample of 18 F-K dwarfs of the young open cluster IC 4665. Stellar parameters and element abundances of Li, O, Mg, Si, Ca, Ti, Cr, Fe and Ni have been derived using the…

Astrophysics · Physics 2009-11-13 Z. -X. Shen , B. Jones , D. N. C. Lin , X. -W. Liu , S. -L. Li

We present [Ffe/H] abundance results that involve a sample of stars with a wide range in luminosity from luminous giants to stars near the turnoff in a globular cluster. Our sample of 25 stars in M71 includes 10 giant stars more luminous…

Astrophysics · Physics 2009-11-06 Solange V. Ramirez , Judith G. Cohen , Jeremy Buss , Michael M. Briley

Open clusters are one of the best astrophysical laboratories we have available for stellar astrophysics studies. This work presents metallicities and individual abundances for fourteen M dwarfs and six G dwarfs from two well-known open…

We present a first systematic investigation of the iron abundance in very hot (Teff>50,000K) hydrogen-deficient post-AGB stars. Our sample comprises 16 PG1159 stars and four DO white dwarfs. We use recent FUSE observations as well as HST…

Astrophysics · Physics 2009-11-07 S. Miksa , J. L. Deetjen , S. Dreizler , J. W. Kruk , T. Rauch , K. Werner

Infrared OH lines at 1.5 - 1.7 um in the H band were obtained with the NIRSPEC high-resolution spectrograph at the 10m Keck Telescope for a sample of seven metal-poor stars. Detailed analyses have been carried out, based on optical…

Astrophysics · Physics 2009-11-07 Jorge Melendez , Beatriz Barbuy

[ABRIDGED] The purpose of this work is to evaluate how several elements produced by different nucleosynthesis processes behave with stellar age and provide empirical relations to derive stellar ages from chemical abundances. We derive…

We present a determination of photospheric parameters and C abundances for a sample of 172 G and K dwarfs, subgiants, and giants with and without detected planets in the solar neighbourhood. The analysis was based on high S/N and high…

Solar and Stellar Astrophysics · Physics 2015-05-20 Ronaldo Da Silva , Andre C. Milone , Bacham E. Reddy

We present a method to determine sodium-abundance ratios ([Na/Fe]) using the Na I D doublet lines in low-resolution ($R \sim$ 2000) stellar spectra. As stellar Na I D lines are blended with those produced by the interstellar medium (ISM),…

Astrophysics of Galaxies · Physics 2022-02-02 Jae-Rim Koo , Young Sun Lee , Hye-Jin Park , Young Kwang Kim , Timothy C. Beers

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

When compared to lithium and beryllium, the absence of boron lines in the optical results in a relatively small data set of boron abundances measured in Galactic stars to date. In this paper we discuss boron abundances published in the…

Solar and Stellar Astrophysics · Physics 2015-05-18 Katia Cunha

We determined the metallicity ([Fe/H]), together with O, Na, Mg, Al, Si, Ca, Ti, Cr and Ni abundances for a sample of 10 unevolved or slightly evolved stars belonging to the open cluster M 67. We find an average metallicity [Fe/H]=0.03 +/-…

Astrophysics · Physics 2009-11-11 S. Randich , P. Sestito , F. Primas , R. Pallavicini , L. Pasquini

Europium abundances for 74 F and G dwarf stars of the galactic disk have been determined from the 4129.7 A Eu II line. The stars were selected from the sample of Edvardsson et al. (1993) and [Eu/Fe] shows a smaller scatter and a slightly…

Astrophysics · Physics 2009-11-07 A. Koch , B. Edvardsson

Using data from the GALAH survey, we explore the dependence of elemental abundances on stellar age and metallicity among Galactic disc stars. We find that the abundance of most elements can be predicted from age and [Fe/H] with an intrinsic…

We present a spectroscopic analysis of a sample of 48 M dwarf stars ($0.2 M_{\odot}< M < 0.6 M_{\odot}$) from the Hyades open cluster using high-resolution H-band spectra from the SDSS/APOGEE survey. Our methodology adopts spectrum…

We present alpha element to iron abundance ratios, [$\alpha$/Fe], for four stars in the outer stellar halo of the Andromeda Galaxy (M 31). The stars were identified as high-likelihood field halo stars by Gilbert et al. (2012) and lie at…

Astrophysics of Galaxies · Physics 2015-06-23 Luis C. Vargas , Karoline M. Gilbert , Marla C. Geha , Erik J. Tollerud , Evan N. Kirby , Puragra Guhathakurta
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