J/A+A/503/545 Equivalent widths of Li, Na, Fe, Ca in NGC 6397 (Lind+, 2009)
Signatures of intrinsic Li depletion and Li-Na anti-correlation in
the metal-poor globular cluster NGC 6397.
Lind K., Primas F., Charbonnel C., Grundahl F., Asplund M.
<Astron. Astrophys. 503, 545 (2009)>
=2009A&A...503..545L 2009A&A...503..545L
ADC_Keywords: Clusters, globular; Stars, late-type; Abundances; Atomic physics
Keywords: stars: abundances - stars: late-type - line: formation
Abstract:
To alleviate the discrepancy between the prediction of the primordial
lithium abundance in the universe and the abundances observed in Pop
II dwarfs and subgiant stars, it has been suggested that the stars
observable today have undergone photospheric depletion of lithium. To
identify the cause of such depletion, it is important to accurately
establish the behaviour of lithium abundance with effective
temperature and evolutionary phase. Stars in globular clusters are
ideal objects for such abundance analysis, as relative stellar
parameters can be precisely determined. We conduct a homogeneous
analysis of a very large sample of stars in the metal-poor globular
cluster NGC 6397, covering well all evolutionary phases from below the
main sequence turn-off to high up the red giant branch. Non-LTE Li
abundances or abundance upper limits are obtained for all stars, and
for a size-able sub-set of the targets also Na abundances are
obtained. The sodium abundances are used to distinguish stars formed
out of pristine material from stars formed out of material affected
by pollution from a previous generation of more massive stars. The
dwarfs, turn-off, and early subgiant stars in our sample form a thin
abundance plateau, disrupted in the middle of the subgiant branch by
the lithium dilution caused by the first dredge-up. A second steep
abundance drop is seen at the luminosity of the red giant branch bump.
The turn-off stars are more lithium-poor, by up to 0.1dex, than
subgiants that have not yet undergone dredge-up. In addition, hotter
dwarfs are slightly more lithium-poor than cooler dwarfs, which may
be a signature of the so-called Li dip in the cluster, commonly seen
among PopI stars. The feature is however weak. A considerably large
spread in Na abundance confirms that NGC6397 has suffered from
intra-cluster pollution in its infancy and a limited number of
Na-enhanced and Li-deficient stars strongly contribute to form a
significant anti-correlation between the abundances of Na and Li.
It is nevertheless seen that lithium abundances are unaffected by
relatively high degrees of pollution. Lithium abundance trends with
effective temperature and stellar luminosity are compared to
predictions from stellar structure models including atomic diffusion
and ad-hoc turbulence below the convection zone. We confirm previous
findings that some turbulence, with strict limits to its efficiency,
is necessary to explain the observations.
Description:
The tables contain coordinates, photometry, derived stellar
parameters, equivalent widths, and abundances for a large number of
dwarfs, subgiant branch stars, and red giant branch stars in the
metal-poor globular cluster NGC6397. All abundances are given in
logarithmic units relative to hydrogen, according to
A(x)=log(N(x)/N(H))+12, where N(x) is the number density of element x
and N(H) the number density of hydrogen. Table 3 contains only a
subset (32) of all targets. The oscillator strengths adopted are
listed in the paper.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 129 517 Photometry and effective temperatures
table3.dat 50 1907 Equivalent widths and Fe abundances for the
UVES targets
table4.dat 129 468 Adopted stellar parameters, equivalent widths
and abundances of Li, Na, and Ca
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See also:
J/PASJ/57/45 : Lithium abundances of F-K stars (Takeda+, 2005)
J/A+A/503/541 : Neutral Li in late-type stars non-LTE calculations (Lind+ 2009)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 7 I7 --- ID1 ? Identification number of target (1)
9- 15 I7 --- ID2 ? Identification number of target (2)
18- 19 I2 h RAh Right Ascension J2000, hours
22- 23 I2 min RAm Right Ascension J2000, minutes
25- 29 F5.2 s RAs Right Ascension J2000, seconds
31 A1 --- DE- Declination J2000, (sign)
32- 33 I2 deg DEd Declination J2000, degrees
36- 37 I2 arcmin DEm Declination J2000, arcminutes
39- 43 F5.2 arcsec DEs Declination J2000, arcseconds
46- 50 F5.1 km/s RV Barycentric radial velocity
53- 58 F6.3 mag Vmag Apparent visual magnitude
61- 65 F5.3 mag (b-y)0 ? Stroemgren colour (b-y) (3)
68- 72 F5.3 mag (v-y)0 ? Stroemgren colour (v-y) (3)
75- 79 F5.3 mag c0 ? Stroemgren colour c1 (3)
81- 84 I4 K T008 ? Effective temperature (O09) (4)
86- 89 I4 K TRM05 ? Effective temperature (RM05) (4)
91- 94 I4 K TA99 ? Effective temperature (A9699) (4)
96- 99 I4 K THa ? Effective temperature (Halpha) (4)
104 A1 --- Rem [abc] Remark (5)
106-129 A24 --- Com Comments
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Note (1): Identification number, this paper
Note (2): Identification number used by Gonzalez-Hernandez et al.
(2009, submitted to A&A).
Note (3): Corrected for reddening
Note (4): Effective temperatures calculated using:
O09 = Onehag et al. (2009, Cat. J/A+A/498/527) relations
RM05 = Ramirez & Melendez (2005ApJ...626..465R 2005ApJ...626..465R) relations
A9699 = Alonso et al. (1996A&A...313..873A 1996A&A...313..873A, 1999A&AS..140..261A 1999A&AS..140..261A) relations
Halpha = Hα-based temperatures
Note (5): Flags as follows:
a = Star observed in the H679.7 setting or in the H665.0 setting
b = Star not observed in the H679.7 setting or in the H665.0 setting
c = Disregarded star with comment
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 7 I7 --- ID1 ? Identification number of target
9- 11 A3 --- Ion [Fe1 Fe2] Element + ionisation stage
15- 22 F8.4 nm Lambda Wavelength of line
25- 29 F5.2 pm EW Equivalent width
33- 36 F4.2 pm e_EW Error on EW
40- 43 F4.2 [---] Abund Iron abundance (log scale, H=12)
47- 50 F4.2 [---] e_Abund Error on Abund
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 7 I7 --- ID1 ? Identification number of target
9- 15 I7 --- ID2 ? Identification number of target
18- 23 F6.3 mag VMAG Absolute visual magnitude
25- 28 I4 K Teff Adopted effective temperature (O09 scale)
30- 33 F4.2 [cm/s2] logg Surface gravity
35- 38 F4.2 km/s Vturb Microturbulence velocity
40- 44 F5.2 [solLum] logLum Logarithm of luminosity
46- 49 F4.2 pm W6707 Equivalent width of LiI 670.7nm line
51- 54 F4.2 pm e_W6707 Error on W6707
56 A1 --- l_ALi Limit flag on ALi (upper limit)
57- 60 F4.2 [---] ALi Lithium abundance
62- 65 F4.2 [---] e_ALi ?=- Error on ALi
67- 70 F4.2 pm W8183 Equivalent width of NaI 818.3nm line
72- 75 F4.2 pm e_W8183 Error on W8183
77- 81 F5.2 pm W8194 Equivalent width of NaI 819.4nm line
83- 86 F4.2 pm e_W8194 Error on W8194
88 A1 --- l_ANa Limit flag on ANa (upper limit)
89- 92 F4.2 [---] ANa Sodium abundance
94- 97 F4.2 [---] e_ANa ?=- Error on ANa
99-103 F5.2 pm W6122 ? Equivalent width of CaI 612.2nm line
105-108 F4.2 pm e_W6122 ? Error on W6122
110-114 F5.2 pm W6162 ? Equivalent width of CaI 616.2nm line
116-119 F4.2 pm e_W6162 ? Error on W6162
121-124 F4.2 [---] ACa ? Calcium abundance
126-129 F4.2 [---] e_ACa ? Error on ACa
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Acknowledgements:
Karin Lind, klind(at)eso.org
(End) Karin Lind [ESO, Germany], Patricia Vannier [CDS] 02-Sep-2009