J/A+A/519/L3 Lithium content of ω Cen (Monaco+, 2010)
The lithium content of ω Centauri. New clues to the cosmological Li
problem from old stars in external galaxies.
Monaco L., Bonifacio P., Sbordone L., Villanova S., Pancino E.
<Astron. Astrophys., 519, L3-3 (2010)>
=2010A&A...519L...3M 2010A&A...519L...3M
ADC_Keywords: Clusters, globular ; Stars, dwarfs ; Abundances
Keywords: nuclear reactions, nucleosynthesis, abundances - stars: abundances -
stars: population II - cosmology: observations -
globular clusters: individual: omega Cen - galaxies: abundances
Abstract:
A discrepancy has emerged between the cosmic lithium abundance
inferred by the WMAP satellite measurement coupled with the prediction
of the standard big-bang nucleosynthesis theory, and the constant Li
abundance measured in metal-poor halo dwarf stars (the so-called Spite
plateau). Several models are being proposed to explain this
discrepancy, involving either new physics, in situ depletion, or the
efficient depletion of Li in the pristine Galaxy by a generation of
massive first stars. The realm of possibilities may be narrowed
considerably by observing stellar populations in different galaxies,
which have experienced different evolutionary histories.
The omega Centauri stellar system is commonly considered as the
remnant of a dwarf galaxy accreted by the Milky Way. We investigate
the lithium content of a conspicuous sample of unevolved stars in this
object.
Description:
We obtained moderate resolution (R=17000) spectra for 91
main-sequence/early sub-giant branch (MS/SGB) omega Cen stars using
the FLAMES-GIRAFFE/VLT spectrograph. Lithium abundances were derived
by matching the equivalent width of the LiI resonance doublet at
6708Å to the prediction of synthetic spectra computed with
different Li abundances. Synthetic spectra were computed using the
SYNTHE code along with ATLAS-9 model atmospheres. The stars effective
temperatures are derived by fitting the wings of the Hα line
with synthetic profiles. Observations were taken on three nights of
27-29 April 2007 using the FLAMES/VLT spectrograph at ESO Paranal.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 65 91 Basic data for MS/SGB stars studied in this paper
table2.dat 61 10 Basic data for SGB-a stars studied in this paper
--------------------------------------------------------------------------------
See also:
J/ApJ/462/241 : Ca abundance for omega Cen red giants (Norris+ 1996)
J/ApJ/667/911 : Abundances on the main sequence of omega Cen (Stanford+, 20007)
J/A+A/527/A18 : EW of 6 subgiants of omega Cen (Pancino+, 2011)
J/A+A/534/A53 : Equivalent widths of 18 subgiant of omega Cen (Pancino+, 2011)
J/MNRAS/357/265 : BVI photometry of omega Cen red giants (Sollima+, 2005)
Byte-by-byte Description of file: table1.dat table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 I6 --- [MBS2010] Sequential number
8- 9 I2 h RAh Right ascension (J2000)
11- 12 I2 min RAm Right ascension (J2000)
14- 18 F5.2 s RAs Right ascension (J2000)
20 A1 --- DE- Declination sign (J2000)
21- 22 I2 deg DEd Declination (J2000)
24- 25 I2 arcmin DEm Declination (J2000)
27- 31 F5.2 arcsec DEs Declination (J2000)
33- 36 F4.1 0.1nm EW ?=- Lithium equivalent width
38- 40 F3.1 0.1nm e_EW ?=- rms uncertainty on EW
42 A1 --- l_A(Li) Limit flag on A(Li)
43- 46 F4.2 [Sun] A(Li) Lithium abundance (uncertainty=0.1dex)
48- 49 I2 --- S/N Signal-to-noise ratio
51- 54 I4 K Teff Hα-based effective temperature
56- 60 F5.2 [Sun] [Fe/H] ?=- Estimated metallicity (1)
61 A1 --- n_[Fe/H] [a] anomalous population SGB-a
(table2 only, assumed metallicity)
62- 65 F4.2 [Sun] e_[Fe/H] ?=- rms uncertainty on [Fe/H]
--------------------------------------------------------------------------------
Note (1): For three stars, no [Fe/H] was estimated. These stars were not
plotted in the bottom panel of Fig. 3.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 02-Jan-2012