J/MNRAS/449/4038 Li abundance of giants in 3 globular clusters (D'Orazi+, 2015)
Lithium abundances in globular cluster giants: NGC 1904, NGC 2808, and NGC 362.
D'Orazi V., Gratton R.G., Angelou G.C., Bragaglia A., Carretta E.,
Lattanzio J.C., Lucatello S., Momany Y., Sollima A., Beccari G.
<Mon. Not. R. Astron. Soc. 449, 4038 (2015)>
=2015MNRAS.449.4038D 2015MNRAS.449.4038D
ADC_Keywords: Clusters, globular ; Stars, population II ; Abundances
Keywords: stars: abundances - stars: Population II -
globular clusters: individual: NGC 1904 -
globular clusters: individual: NGC 2808 -
globular clusters: individual: NGC 362
Abstract:
The presence of multiple populations in globular clusters has been
well established thanks to high-resolution spectroscopy. It is widely
accepted that distinct populations are a consequence of different
stellar generations: intra-cluster pollution episodes are required to
produce the peculiar chemistry observed in almost all clusters.
Unfortunately, the progenitors responsible have left an ambiguous
signature and their nature remains unresolved. To constrain the
candidate polluters, we have measured lithium and aluminium abundances
in more than 180 giants across three systems: NGC 1904, NGC 2808, and
NGC 362. The present investigation along with our previous analysis of
M12 and M5 affords us the largest database of simultaneous
determinations of Li and Al abundances. Our results indicate that Li
production has occurred in each of the three clusters. In NGC 362 we
detected an M12-like behaviour, with first and second-generation stars
sharing very similar Li abundances favouring a progenitor that is able
to produce Li, such as AGB stars. Multiple progenitor types are
possible in NGC 1904 and NGC 2808, as they possess both an
intermediate population comparable in lithium to the first generation
stars and also an extreme population, that is enriched in Al but
depleted in Li. A simple dilution model fails in reproducing this
complex pattern. Finally, the internal Li variation seems to suggest
that the production efficiency of this element is a function of the
cluster's mass and metallicity - low-mass or relatively metal-rich
clusters are more adept at producing Li.
Description:
Observations were carried out in visitor mode with FLAMES mounted at
UT2 of ESO-VLT on 2014 December 11-13 (Program 094.D-0363(A)).
Spectra were collected with the scientific aim of inferring Li and Al
abundances for large samples of RGB stars, below and above the RGB
bump luminosity, in several GCs, as part of our dedicated survey (see
Paper I, D'Orazi et al., 2014ApJ...791...39D 2014ApJ...791...39D).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 100 185 Photometry, stellar parameters, kinematics, and
chemical information for our sample stars
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See also:
J/A+A/548/A92 : VrI light curves of NGC1904 variables (Kains+, 2012)
J/MNRAS/437/1609 : NGC 2808 HB stars abundances (Marino+, 2014)
J/MNRAS/437/1609 : NGC 2808 HB stars abundances (Marino+, 2014)
J/A+A/557/A138 : Detailed chemical abundances in NGC 362 (Carretta+ 2013)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- NGC NGC number of globular cluster (1)
5 A1 --- --- [-]
6- 10 I5 --- ID Star identification in cluster (1)
12- 13 I2 h RAh Right ascension J2000, Epoch 2000
15- 16 I2 min RAm Right Ascension J2000
18- 22 F5.2 s RAs Right Ascension J2000
24 A1 --- DE- Declination sign J2000
25- 26 I2 deg DEd Declination J2000, Epoch 2000
28- 29 I2 arcmin DEm Declination J2000
31- 34 F4.1 arcsec DEs Declination J2000
36- 41 F6.3 mag Bmag B magnitude
43- 48 F6.3 mag Vmag V magnitude
50- 55 F6.3 mag Ksmag ? 2MASS Ks magnitude
57- 62 F6.2 km/s RV [83/239] Heliocentric radial velocity
64- 66 I3 --- S/N [90/211] Signal-to-noise ratio at 6708Å
68- 71 I4 K Teff [4425/5183] Effective temperature
73- 76 F4.2 cm/s2 logg [1.1/2.9] Surface gravity
78- 81 F4.2 km/s xi [1.9/1.9] Microturbulence velocity ξ
83 A1 --- l_A(Li)e [<] Upper limit on Li abundance
84- 87 F4.2 [-] A(Li)e [0/1.13]? LTE Li abundance
89 A1 --- l_A(Li)n [<] Upper limit on Li abundance
90- 93 F4.2 [-] A(Li)n [0/1.21]? non-LTE Li abundance
95 A1 --- l_[Al/Fe] [<] Upper limit on Al/Fe
96-100 F5.2 [Sun] [Al/Fe] [-0.3/0.98]? Aluminium abundances
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Note (1): Star identification as NNNN-NNNNN where the first number is
the NGC number, and the second number the Star number.
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Acknowledgements:
Valentina D'Orazi, valentina.dorazi(at)oapd.inaf.it
(End) Patricia Vannier [CDS] 17-Apr-2015