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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Constraining cosmic scatter in the Galactic halo through a differential analysis of metal-poor stars

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Reggiani, Henrique [1, 2] ; Melendez, Jorge [2] ; Kobayashi, Chiaki [3] ; Karakas, Amanda [4] ; Placco, Vinicius [5]
Total Authors: 5
[1] Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg - Germany
[2] Univ Sao Paulo, Dept Astron, IAG, Inst Astron Geofis & Ciencias Atmosfer, Rua Matao 1226, Cidade Univ, BR-05508900 Sao Paulo, SP - Brazil
[3] Univ Hertfordshire, Sch Phys Astron & Math, Ctr Astrophys Res, Coll Lane, Hatfield AL10 9AB, Herts - England
[4] Monash Univ, Sch Phys & Astron, Monash Ctr Astrophys, Clayton, Vic 3800 - Australia
[5] Univ Notre Dame, Dept Phys, JINA Ctr Evolut Elements, Notre Dame, IN 46556 - USA
Total Affiliations: 5
Document type: Journal article
Source: Astronomy & Astrophysics; v. 608, DEC 5 2017.
Web of Science Citations: 11

Context. The chemical abundances of metal-poor halo stars are important to understanding key aspects of Galactic formation and evolution. Aims. We aim to constrain Galactic chemical evolution with precise chemical abundances of metal-poor stars (2.8 <= {[}Fe/H] <= -1.5). Methods. Using high resolution and high S/N UVES spectra of 23 stars and employing the differential analysis technique we estimated stellar parameters and obtained precise LTE chemical abundances. Results. We present the abundances of Li, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Zn, Sr, Y, Zr, and Ba. The differential technique allowed us to obtain an unprecedented low level of scatter in our analysis, with standard deviations as low as 0.05 dex, and mean errors as low as 0.05 dex for {[}X/Fe]. Conclusions. By expanding our metallicity range with precise abundances from other works, we were able to precisely constrain Galactic chemical evolution models in a wide metallicity range (3.6 <= {[}Fe/H] <= 0.4). The agreements and discrepancies found are key for further improvement of both models and observations. We also show that the LTE analysis of Cr II is a much more reliable source of abundance for chromium, as Cr I has important NLTE effects. These effects can be clearly seen when we compare the observed abundances of Cr I and Cr II with GCE models. While Cr I has a clear disagreement between model and observations, Cr II is very well modeled. We confirm tight increasing trends of Co and Zn toward lower metallicities, and a tight flat evolution of Ni relative to Fe. Our results strongly suggest inhomogeneous enrichment from hypernovae. Our precise stellar parameters results in a low star-to-star scatter (0.04 dex) in the Li abundances of our sample, with a mean value about 0.4 dex lower than the prediction from standard Big Bang nucleosynthesis; we also study the relation between lithium depletion and stellar mass, but it is difficult to assess a correlation due to the limited mass range. We find two blue straggler stars, based on their very depleted Li abundances. One of them shows intriguing abundance anomalies, including a possible zinc enhancement, suggesting that zinc may have been also produced by a former AGB companion. (AU)

FAPESP's process: 12/24392-2 - High precision spectroscopy: impact in the study of planets, stars, the galaxy and cosmology
Grantee:Jorge Luis Melendez Moreno
Support type: Research Projects - Thematic Grants
FAPESP's process: 14/18100-4 - Stellar populations in the Milky Way: bulge, halo, disk and star forming regions; instrumentation for high resolution spectroscopy
Grantee:Beatriz Leonor Silveira Barbuy
Support type: Research Projects - Thematic Grants