Li-rich giant stars under scrutiny: binarity, magnetic activity, and the evolutionary status after Gaia DR2

Costa, Jefferson Soares da; Almeida, Leandro de; Castro, Matthieu Sebastien; Nascimento Júnior, José Dias do; Gonçalves, B. F. O

Li-rich giant stars under scrutiny: binarity, magnetic activity, and the evolutionary status after Gaia DR2

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dc.contributor.author	Costa, Jefferson Soares da
dc.contributor.author	Almeida, Leandro de
dc.contributor.author	Castro, Matthieu Sebastien
dc.contributor.author	Nascimento Júnior, José Dias do
dc.contributor.author	Gonçalves, B. F. O
dc.date.accessioned	2020-12-15T19:44:08Z
dc.date.available	2020-12-15T19:44:08Z
dc.date.issued	2020-09-02
dc.description.resumo	We present a study of the evolutionary state of a few lithium-rich giant stars based on the Gaia Data Release 2 (DR2) parallaxes and photometry. We also investigate the chromospheric activity, the presence of a surface magnetic field, and the radial velocity for our sample stars. We analysed both archive and new data. We gathered archive spectra from several instruments, mainly ELODIE and NARVAL, and we added new data acquired with the spectrograph MUSICOS. We applied the least-squares deconvolution technique to obtain Stokes V and I mean profiles to compute longitudinal magnetic field for a subset. Moreover, for the same subset, we analysed the Ca II H&K emission lines to calculate the S-index. We also derived atmospheric parameters and Li abundances for all 18 stars of our sample. We found that stars previously classified as red giant branch (RGB) may actually be at a different evolutionary state. Furthermore, we identified that most stars in our sample with detection of surface magnetic field show at least moderate rotation velocities, but none the less, we could not detect a magnetic field in two fast rotators. Because of our small sample of magnetic giants, it is difficult to determine if the presence of surface magnetic field and the Li-rich giant phenomena could be somehow linked. The large variation of the radial velocity of part of our sample indicates that some of them might have a binary companion, which may change the way we look at the Li problem in giant stars	pt_BR
dc.identifier.citation	GONÇALVES, B F O; DA COSTA, J. S.; ALMEIDA, L; CASTRO, M; NASCIMENTO, J. D. Li-rich giant stars under scrutiny: binarity, magnetic activity, and the evolutionary status after gaia dr2. Monthly Notices of the Royal Astronomical Society, [S.L.], v. 498, n. 2, p. 2295-2308, 2 set. 2020. Disponível em: https://academic.oup.com/mnras/article-abstract/498/2/2295/5900561?redirectedFrom=fulltext. Acesso em: 07 out. 2020. http://dx.doi.org/10.1093/mnras/staa2408.	pt_BR
dc.identifier.doi	10.1093/mnras/staa2408
dc.identifier.issn	0035-8711
dc.identifier.issn	1365-2966
dc.identifier.uri	https://repositorio.ufrn.br/handle/123456789/31005
dc.language	en	pt_BR
dc.publisher	Oxford University Press	pt_BR
dc.subject	Techniques: radial velocities – techniques	pt_BR
dc.subject	Spectroscopic – stars	pt_BR
dc.subject	Abundances – stars	pt_BR
dc.subject	Evolution – stars	pt_BR
dc.subject	Late-type – stars	pt_BR
dc.subject	Magnetic field	pt_BR
dc.title	Li-rich giant stars under scrutiny: binarity, magnetic activity, and the evolutionary status after Gaia DR2	pt_BR
dc.type	article	pt_BR