2009A&A...505L..13G


Query : 2009A&A...505L..13G

2009A&A...505L..13G - Astronomy and Astrophysics, volume 505, L13-16 (2009/10-2)

Lithium in the globular cluster NGC 6397. Evidence for dependence on evolutionary status.

GONZALEZ HERNANDEZ J.I., BONIFACIO P., CAFFAU E., STEFFEN M., LUDWIG H.-G., BEHARA N.T., SBORDONE L., CAYREL R. and ZAGGIA S.

Abstract (from CDS):

Most globular clusters are believed to host a single stellar population. They can thus be considered a good place to study the Spite plateau and to search for possible evolutionary modifications of the Li content. We want to determine the Li content of subgiant (SG) and main sequence (MS) stars of the old, metal-poor globular cluster NGC 6397. This work was aimed not only at studying possible Li abundance variations but also to investigate the cosmological Li discrepancy. Here, we present FLAMES/GIRAFFE observations of a sample of 84 SG and 79 MS stars in NGC 6397 selected in a narrow range of B-V colour and, therefore, effective temperatures. We determine both effective temperatures and Li abundances using three-dimensional hydrodynamical model atmospheres for all the MS and SG stars of the sample. We find a significant difference in the Li abundance between SG stars and MS stars, the SG stars having an abundance higher by almost 0.1dex on average. We also find a decrease in the lithium abundance with decreasing effective temperature, both in MS and SG stars, albeit with a significantly different slope for the two classes of stars. This suggests that the lithium abundance in these stars is, indeed, altered by some process, which is temperature-dependent. The lithium abundance pattern observed in NGC 6397 is different from what is found among field stars, casting some doubt on the use of globular cluster stars as representative of Population II with respect to the lithium abundance. None of the available theories of Li depletion appears to satisfactorily describe our observations.

Abstract Copyright:

Journal keyword(s): stars: abundances - stars: atmospheres - stars: population II - stars: fundamental parameters - Galaxy: globular clusters: individual: NGC 6397

VizieR on-line data: <Available at CDS (J/A+A/505/L13): table2.dat>

Nomenclature: Table 2: [GBC2009] AAANNNNNN N=79+84 among (Nos MSS001253-049487, SGB001167-036901).

Status at CDS : All or part of tables of objects could be ingested in SIMBAD with priority 2.

Simbad objects: 15

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Number of rows : 15
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 NGC 104 GlC 00 24 05.359 -72 04 53.20   5.78 4.09     ~ 3673 0
2 HD 74000 PM* 08 40 50.8038415228 -16 20 42.513275817 9.84 10.09 9.66     F2 254 0
3 HD 84937 PM* 09 48 56.09801 +13 44 39.3237 8.49 8.68 8.32 7.97 7.70 F8Vm-5 745 0
4 HD 140283 Pe* 15 43 03.0967798658 -10 56 00.595803430 7.508 7.711 7.212 6.63 8.21 F9VkA5mA1 884 0
5 2MASS J17394372-5340506 RG* 17 39 43.7301237110 -53 40 50.712482307   16.44 15.966   15.05 ~ 4 0
6 2MASS J17395095-5342479 RG* 17 39 50.956 -53 42 47.90   16.54 16.060     ~ 3 0
7 2MASS J17400610-5342244 RG* 17 40 06.1031268334 -53 42 24.512150663   16.47 15.951     ~ 3 0
8 2MASS J17400635-5342090 RG* 17 40 06.354 -53 42 09.05   16.48 15.973   15.07 ~ 4 0
9 [LPC2009] 11444 RG* 17 40 14.89 -53 38 37.9   16.42 15.901     ~ 3 0
10 2MASS J17402118-5337566 RG* 17 40 21.188 -53 37 56.68   16.53 16.086     ~ 3 0
11 [LPC2009] 13535 RG* 17 40 21.3897517439 -53 43 05.414224834   16.50 15.988   15.12 ~ 4 0
12 2MASS J17402414-5338353 RG* 17 40 24.1546093286 -53 38 35.392271328   16.44 15.925     ~ 3 0
13 2MASS J17402767-5342161 RG* 17 40 27.6740628712 -53 42 16.176808669   16.41 15.916     ~ 3 0
14 NGC 6397 GlC 17 40 42.09 -53 40 27.6   7.39 5.17     ~ 1853 1
15 NGC 6752 GlC 19 10 52.11 -59 59 04.4   6.96 6.28     ~ 1866 0

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2021.11.30-16:03:13

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