The Chemical Compositions of Very Metal-Poor Stars Hd 122563 and Hd 140283: A View From the Infrared

Afşar, Melike; Sneden, Christopher; Frebel, Anna; Kim, Hwi; Mace, Gregory N.; Kaplan, Kyle; Lee, Hye-In; Oh, Hyun-Mee; Oh, Jae Sok; Pak, Soojong; Park, Chan; Pavel, M.; Yuk, In-Soo; Jaffe, D. T.

doi:10.3847/0004-637x/819/2/103

Cited by 30 publications

(21 citation statements)

References 47 publications

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“…More detailed and extended descriptions of IGRINS are given in Yuk et al (2010) and Park et al (2014). A discussion of our observational techniques and reduction processes is given in Afşar et al (2016) (hereafter Afşar16). Figure 1 and Figure 2 shows the ready-for-analysis spectra of three RHB stars: wavelength-calibrated, continuumnormalized, telluric-line-removed, and merged into a single continuous spectrum.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

Chemical Compositions of Evolved Stars from Near-infrared IGRINS High-resolution Spectra. I. Abundances in Three Red Horizontal Branch Stars

Afşar

Sneden

Wood

et al. 2018

ApJ

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We have derived elemental abundances of three field red horizontal branch stars using high-resolution (R 45,000), high signal-to-noise ratio (S/N 200) H and K band spectra obtained with the Immersion Grating Infrared Spectrograph (IGRINS). We have determined the abundances of 21 elements including α (Mg, Si, Ca, S), odd-Z (Na, Al, P, K), Fe-group (Sc, Ti, Cr, Co, Ni), neutron-capture (Ce, Nd, Yb), and CNO group elements. S, P and K are determined for the first time in these stars. H and K band spectra provide a substantial number of S i lines, which potentially can lead to a more robust exploration of the role of sulfur in the cosmochemical evolution of the Galaxy. We have also derived 12 C/ 13 C ratios from synthetic spectra of the first overtone (2−0) and (3−1) 12 CO and (2−0) 13 CO lines near 23440Å and 13 CO (3−1) lines at about 23730Å. Comparison of our results with the ones obtained from the optical region suggests that the IGRINS high-resolution H and K band spectra offer more internally self-consistent atomic lines of the same species for several elements, especially the α elements. This in turn provides more reliable abundances for the elements with analytical difficulties in the optical spectral range.

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Section: Observations and Data Reductionmentioning

confidence: 99%

Chemical Compositions of Evolved Stars from Near-infrared IGRINS High-resolution Spectra. I. Abundances in Three Red Horizontal Branch Stars

Afşar

Sneden

Wood

et al. 2018

ApJ

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“…An increasing number of these stars are now known (e.g., Hansen et al 2018, and other ongoing work by the R-Process Alliance). Their proximity to the Sun permits detailed abundance inventories to be derived from optical, ultraviolet, and near-infrared spectra (e.g., Sneden et al 1998;Roederer et al 2012a;Afşar et al 2016). Five-parameter astrometric solutions (parallax, right ascension, declination, proper motion in right ascension, proper motion in declination) are now available for many of these stars in the second data release of the Gaia mission (DR2; Lindegren et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Kinematics of Highly r-process-enhanced Field Stars: Evidence for an Accretion Origin and Detection of Several Groups from Disrupted Satellites

2018

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We present kinematics of 35 highly r-process-enhanced ([Eu/Fe] ≥ +0.7) metal-poor (−3.8 < [Fe/H] < −1.4) field stars. We calculate six-dimensional positions and velocities, evaluate energies and integrals of motion, and compute orbits for each of these stars using parallaxes and proper motions from the second Gaia data release and published radial velocities. All of these stars have halo kinematics. Most stars (66%) remain in the inner regions of the halo (< 13 kpc), and many (51%) have orbits that pass within 2.6 kpc of the Galactic center. Several stars (20%) have orbits that extend beyond 20 kpc, including one with an orbital apocenter larger than the Milky Way virial radius. We apply three clustering methods to search for structure in phase space, and we identify eight groups. No abundances are considered in the clustering process, but the [Fe/H] dispersions of the groups are smaller than would be expected by random chance. The orbital properties, clustering in phase space and metallicity, and lack of highly r-process-enhanced stars on disk-like orbits indicate that such stars likely were accreted from disrupted satellites. Comparison with the galaxy luminosity-metallicity relation suggests M V −9 for most of the progenitor satellites, characteristic of ultra-faint or low-luminosity classical dwarf spheroidal galaxies. Environments with low rates of star formation and Fe production, rather than the nature of the r-process site, may be key to obtaining the [Eu/Fe] ratios found in highly r-process-enhanced stars.

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“…Since its discovery by Wallerstein et al (1963), HD 122563 has been the subject of numerous spectroscopic analyses (e.g. Westin et al 2000;Barbuy et al 2003;Cowan et al 2005;Aoki et al 2007;Afşar et al 2016;Dobrovolskas et al 2015;Prakapavičius et al 2017); a wealth of photometric data is also available for this star in a variety of filter systems (e.g. Hauck & Mermilliod 1998;Ducati 2002;Cutri et al 2003).…”

Section: Introductionmentioning

confidence: 99%

The benchmark halo giant HD 122563: CNO abundances revisited with three-dimensional hydrodynamic model stellar atmospheres

Collet

Nordlund

Asplund

et al. 2018

Monthly Notices of the Royal Astronomical Society

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We present an abundance analysis of the low-metallicity benchmark red giant star HD 122563 based on realistic, state-of-the-art, high-resolution, three-dimensional (3D) model stellar atmospheres including non-grey radiative transfer through opacity binning with four, twelve, and 48 bins. The 48-bin 3D simulation reaches temperatures lower by ∼ 300 − 500 K than the corresponding 1D model in the upper atmosphere. Small variations in the opacity binning, adopted line opacities, or chemical mixture can cool the photospheric layers by a further ∼100 − 300 K and alter the effective temperature by ∼100 K.A 3D local thermodynamic equilibrium (LTE) spectroscopic analysis of Fe and Fe lines gives discrepant results in terms of derived Fe abundance, which we ascribe to non-LTE effects and systematic errors on the stellar parameters. We also determine C, N, and O abundances by simultaneously fitting CH, OH, NH, and CN molecular bands and lines in the ultraviolet, visible, and infrared. We find a small positive 3D−1D abundance correction for carbon (+0.03 dex) and negative ones for nitrogen (−0.07 dex) and oxygen (−0.34 dex). From the analysis of the [O ] line at 6300.3 Å, we derive a significantly higher oxygen abundance than from molecular lines (+0.46 dex in 3D and +0.15 dex in 1D). We rule out important OH photodissociation effects as possible explanation for the discrepancy and note that lowering the surface gravity would reduce the oxygen abundance difference between molecular and atomic indicators.

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The Chemical Compositions of Very Metal-Poor Stars Hd 122563 and Hd 140283: A View From the Infrared

Cited by 30 publications

References 47 publications

Chemical Compositions of Evolved Stars from Near-infrared IGRINS High-resolution Spectra. I. Abundances in Three Red Horizontal Branch Stars

Chemical Compositions of Evolved Stars from Near-infrared IGRINS High-resolution Spectra. I. Abundances in Three Red Horizontal Branch Stars

Kinematics of Highly r-process-enhanced Field Stars: Evidence for an Accretion Origin and Detection of Several Groups from Disrupted Satellites

The benchmark halo giant HD 122563: CNO abundances revisited with three-dimensional hydrodynamic model stellar atmospheres

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