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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.)

GRACES observations of young [alpha/Fe]-rich stars

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Author(s):
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Yong, David [1] ; Casagrande, Luca [1] ; Venn, Kim A. [2] ; Chene, Andre-Nicolas [3] ; Keown, Jared [2] ; Malo, Lison [4] ; Martioli, Eder [5] ; Alves-Brito, Alan [6] ; Asplund, Martin [1] ; Dotter, Aaron [1] ; Martell, Sarah L. [7] ; Melendez, Jorge [8] ; Schlesinger, Katharine J. [1]
Total Authors: 13
Affiliation:
[1] Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611 - Australia
[2] Univ Victoria, Dept Phys & Astron, Victoria, BC V8W 3P2 - Canada
[3] Northern Operat Ctr, Gemini Observ, 670 North Aohoku Pl, Hilo, HI 96720 - USA
[4] Canada France Hawaii Telescope Corp, 65-1238 Mamalahoa Highway, Kamuela, HI 96743 - USA
[5] Lab Nacl Astrofis LNA MCTI, Rua Estados Unidos 154, Itajuba, MG - Brazil
[6] Univ Fed Rio Grande do Sul, Inst Fis, Av Bento Goncalves 9500, Porto Alegre, RS - Brazil
[7] Univ New S Wales, Sch Phys, Sydney, NSW 2052 - Australia
[8] Univ Sao Paulo, IAG USP, Dept Astron, Rua Matao 1226, Cidade Univ, BR-05508900 Sao Paulo, SP - Brazil
Total Affiliations: 8
Document type: Journal article
Source: Monthly Notices of the Royal Astronomical Society; v. 459, n. 1, p. 487-495, JUN 11 2016.
Web of Science Citations: 21
Abstract

We measure chemical abundance ratios and radial velocities in four massive (i.e. young) {[}alpha/Fe]-rich red giant stars using high-resolution high-S/N spectra from ESPaDOnS fed by Gemini-GRACES. Our differential analysis ensures that our chemical abundances are on the same scale as the Alves-Brito et al. (2010) study of bulge, thin, and thick disc red giants. We confirm that the program stars have enhanced {[}alpha/Fe] ratios and are slightly metal poor. Aside from lithium enrichment in one object, the program stars exhibit no chemical abundance anomalies when compared to giant stars of similar metallicity throughout the Galaxy. This includes the elements Li, O, Si, Ca, Ti, Cr, Ni, Cu, Ba, La, and Eu. Therefore, there are no obvious chemical signatures that can help to reveal the origin of these unusual stars. While our new observations show that only one star (not the Li-rich object) exhibits a radial velocity variation, simulations indicate that we cannot exclude the possibility that all four could be binaries. In addition, we find that two (possibly three) stars show evidence for an infrared excess, indicative of a debris disc. This is consistent with these young {[}alpha/Fe]-rich stars being evolved blue stragglers, suggesting their apparent young age is a consequence of a merger or mass transfer. We would expect a binary fraction of similar to 50 per cent or greater for the entire sample of these stars, but the signs of the circumbinary disc may have been lost since these features can have short time-scales. Radial velocity monitoring is needed to confirm the blue straggler origin. (AU)

FAPESP's process: 10/50930-6 - Chemical evolution and galactic and extragalactic stellar populations, by means of spectroscopy and imaging
Grantee:Beatriz Leonor Silveira Barbuy
Support type: Research Projects - Thematic Grants