J/A+A/634/A130 Lithium abundances in microlensed bulge dwarfs (Bensby+, 2020)
Chemical evolution of the Galactic bulge as traced by microlensed dwarf and
subgiant stars. VII. Lithium.
Bensby T., Feltzing S., Yee J., Johnson J.A., Gould A., Asplund M.,
Melendez J., Lucatello S.
<Astron. Astrophys. 634, A130 (2020)>
=2020A&A...634A.130B 2020A&A...634A.130B (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Stars, G-type ; Abundances
Keywords: gravitational lensing: micro - Galaxy: bulge - Galaxy: formation -
Galaxy: evolution - stars: abundances
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 6707Å 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 0.4-0.5dex 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.
Description:
We perform a detailed analysis of Li in 91 microlensed dwarf stars in
the Galactic bulge. Li abundances were determined through spectral
line synthesis of the Li feature at 670.8 nm. The stellar sample
traces the evolution of the Galactic bulge, and is the same as
previously analysed by Bensby et al. (2017A&A...605A..89B 2017A&A...605A..89B, Cat.
J/A+A/605/A89) where stellar parameters and ages were taken from.
For each star we give the NLTE corrected Li abundance, the applied
NLTE correction, and uncertainties in the form of NLTE corrected Li
abundances based on the same analysis but increasing and decreasing
the effective temperatures with their uncertainties. 22 stars have
"good" Li abundances (flag=0 in Flag column), and 69 stars have upper
Li upper limits (flag=1 in Flag column). The uncertainties are not
given for the stars with Li upper limit abundances
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 50 91 Li abundances and uncertainties
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See also:
J/A+A/615/A151 : Li abundances in 714 F and G dwarf stars (Bensby+, 2018)
J/A+A/605/A89 : Abundances of microlensed bulge stars. VI. (Bensby+, 2017)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- Name Name of microlensing source star
21- 26 I6 --- Num Internal numbering of star
28- 32 F5.2 --- ALi NLTE corrected Li abundance
34- 37 F4.2 --- ALil ? NLTE corrected lower Li abundance
39- 42 F4.2 --- ALiu ? NLTE corrected upper Li abundance
44- 48 F5.2 --- NLTE NLTE correction that were applied
50 I1 --- l_ALi [0/1] Limit flag on ALi (1)
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Note (1): Limit flag on ALi as follows;
1 = upper limit
0 = well-detected Li line
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Acknowledgements:
Thomas Bensby, tbensby(at)astro.lu.se
References:
Bensby et al., Paper I 2009A&A...499..737B 2009A&A...499..737B, Cat. J/A+A/499/737
Bensby et al., Paper II 2010A&A...512A..41B 2010A&A...512A..41B, Cat. J/A+A/512/A41
Bensby et al., Paper III 2010A&A...521L..57B 2010A&A...521L..57B
Bensby et al., Paper IV 2011A&A...533A.134B 2011A&A...533A.134B, Cat. J/A+A/533/A134
Bensby et al., Paper V 2013A&A...549A.147B 2013A&A...549A.147B, Cat. J/A+A/549/A147
Bensby et al., Paper VI 2017A&A...605A..89B 2017A&A...605A..89B, Cat. J/A+A/605/A89
(End) Thomas Bensby [Lund Obs., Sweden], Patricia Vannier [CDS] 22-Jan-2020