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Chemical evolution of the Galactic bulge as traced by microlensed dwarf and subgiant stars : VII. Lithium

Bensby, T. LU orcid ; Feltzing, S. LU orcid ; Yee, J. C. ; Johnson, J. A. LU ; Gould, A. ; Asplund, M. ; Meléndez, J. and Lucatello, S. (2020) In Astronomy and Astrophysics 634.
Abstract

Lithium abundances are presented for 91 dwarf and subgiant stars in the Galactic bulge. The analysis is based on line synthesis of the 7Li line at 6707 Å in high-resolution spectra obtained during gravitational microlensing events, when the brightnesses of the targets were highly magnified. Our main finding is that bulge stars at sub-solar metallicities that are older than about eight billion years do not show any sign of Li production; that is, the Li trend with metallicity is flat or even slightly declining. This indicates that no lithium was produced during the first few billion years in the history of the bulge. This finding is essentially identical to what is seen for the (old) thick disk stars in the solar neighbourhood, and adds... (More)

Lithium abundances are presented for 91 dwarf and subgiant stars in the Galactic bulge. The analysis is based on line synthesis of the 7Li line at 6707 Å in high-resolution spectra obtained during gravitational microlensing events, when the brightnesses of the targets were highly magnified. Our main finding is that bulge stars at sub-solar metallicities that are older than about eight billion years do not show any sign of Li production; that is, the Li trend with metallicity is flat or even slightly declining. This indicates that no lithium was produced during the first few billion years in the history of the bulge. This finding is essentially identical to what is seen for the (old) thick disk stars in the solar neighbourhood, and adds another piece of evidence for a tight connection between the metal-poor bulge and the Galactic thick disk. For the bulge stars younger than about eight billion years, the sample contains a group of stars at very high metallicities at [Fe/H]  ≈  +0.4 that have lithium abundances in the range A(Li)  =  2.6 - 2.8. In the solar neighbourhood the lithium abundances have been found to peak at A(Li)  ≈  3.3 at [Fe/H]  ≈  +0.1 and then decrease by 0.4-0.5 dex when reaching [Fe/H]  ≈  +0.4. The few bulge stars that we have at these metallicities seem to support this declining A(Li) trend. This could indeed support the recent claim that the low A(Li) abundances at the highest metallicities seen in the solar neighbourhood could be due to stars from the inner disk, or the bulge region, that have migrated to the solar neighbourhood.

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author
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organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Galaxy: bulge, Galaxy: evolution, Galaxy: formation, Gravitational lensing: micro, Stars: abundances
in
Astronomy and Astrophysics
volume
634
article number
A130
publisher
EDP Sciences
external identifiers
  • scopus:85089144715
ISSN
0004-6361
DOI
10.1051/0004-6361/201937401
language
English
LU publication?
yes
id
03056c84-dd4c-44de-8371-ff3a3f4159ad
date added to LUP
2020-08-19 08:54:39
date last changed
2022-12-24 00:27:00
@article{03056c84-dd4c-44de-8371-ff3a3f4159ad,
  abstract     = {{<p>Lithium abundances are presented for 91 dwarf and subgiant stars in the Galactic bulge. The analysis is based on line synthesis of the 7Li line at 6707 Å in high-resolution spectra obtained during gravitational microlensing events, when the brightnesses of the targets were highly magnified. Our main finding is that bulge stars at sub-solar metallicities that are older than about eight billion years do not show any sign of Li production; that is, the Li trend with metallicity is flat or even slightly declining. This indicates that no lithium was produced during the first few billion years in the history of the bulge. This finding is essentially identical to what is seen for the (old) thick disk stars in the solar neighbourhood, and adds another piece of evidence for a tight connection between the metal-poor bulge and the Galactic thick disk. For the bulge stars younger than about eight billion years, the sample contains a group of stars at very high metallicities at [Fe/H]  ≈  +0.4 that have lithium abundances in the range A(Li)  =  2.6 - 2.8. In the solar neighbourhood the lithium abundances have been found to peak at A(Li)  ≈  3.3 at [Fe/H]  ≈  +0.1 and then decrease by 0.4-0.5 dex when reaching [Fe/H]  ≈  +0.4. The few bulge stars that we have at these metallicities seem to support this declining A(Li) trend. This could indeed support the recent claim that the low A(Li) abundances at the highest metallicities seen in the solar neighbourhood could be due to stars from the inner disk, or the bulge region, that have migrated to the solar neighbourhood. </p>}},
  author       = {{Bensby, T. and Feltzing, S. and Yee, J. C. and Johnson, J. A. and Gould, A. and Asplund, M. and Meléndez, J. and Lucatello, S.}},
  issn         = {{0004-6361}},
  keywords     = {{Galaxy: bulge; Galaxy: evolution; Galaxy: formation; Gravitational lensing: micro; Stars: abundances}},
  language     = {{eng}},
  publisher    = {{EDP Sciences}},
  series       = {{Astronomy and Astrophysics}},
  title        = {{Chemical evolution of the Galactic bulge as traced by microlensed dwarf and subgiant stars : VII. Lithium}},
  url          = {{http://dx.doi.org/10.1051/0004-6361/201937401}},
  doi          = {{10.1051/0004-6361/201937401}},
  volume       = {{634}},
  year         = {{2020}},
}