J/A+A/490/777 Abundances of Population II stars in NGC 6397 (Lind+, 2008)
Atomic diffusion and mixing in old stars.
II. Observations of stars in the globular cluster NGC 6397 with
VLT/FLAMES-GIRAFFE.
Lind K., Korn A.J., Barklem P.S., Grundahl F.
<Astron. Astrophys., 490, 777-786 (2008)>
=2008A&A...490..777L 2008A&A...490..777L
ADC_Keywords: Clusters, globular ; Stars, population II ; Abundances
Keywords: stars: abundances - stars: Population II -
globular clusters: general - techniques: spectroscopic -
methods: observational - diffusion
Abstract:
Evolutionary trends in the surface abundances of heavier elements have
recently been identified in the globular cluster NGC 6397 ([Fe/H]=-2),
indicating the operation of atomic diffusion in these stars. Such
trends constitute important constraints for the extent to which
diffusion modifies the internal structure and surface abundances of
solar-type, metal-poor stars.
We perform an independent check of the reality and size of abundance
variations within this metal-poor globular cluster.
Observational data covering a large stellar sample, located between
the cluster turn-off point and the base of the red giant branch, are
homogeneously analysed. The spectroscopic data were obtained with the
medium-high resolution spectrograph FLAMES/GIRAFFE on VLT-UT2
(R∼27000). We derive independent effective-temperature scales from
profile fitting of Balmer lines and by applying colour-Teff
calibrations to Stroemgren uvby and broad-band BVI photometry. An
automated spectral analysis code is used together with a grid of MARCS
model atmospheres to derive stellar surface abundances of Mg, Ca, Ti,
and Fe.
Description:
The target selection for the spectroscopic study is based on
Stroemgren uvby photometry. The photometric observations were
collected with the DFOSC instrument on the 1.5m telescope on La
Silla, Chile, in 1997. Additional BVI photometric data were obtained
in 2005.
All spectroscopic data were collected in Service Mode, with the
fibre-fed, multi-object, medium-high resolution spectrograph
FLAMES/GIRAFFE at ESO-VLT. FLAMES allows for 132 objects to be
observed simultaneously, with GIRAFFE in MEDUSA mode, between 2005 Mar
23 and Apr 04.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 107 116 Stellar abundances derived for the sample stars
table5.dat 67 86 List of lines used in the abundance analysis,
with references to the oscillator strengths used
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See also:
J/A+A/287/769 : UV photometry of NGC 6397 (Burgarella+ 1994)
J/ApJS/99/637 : Equivalent widths for 54 red giants (Norris+ 1995)
J/PASP/108/682 : Low-Mass Stars in Outer Field in NGC 6397 (Mould+, 1996)
J/A+AS/122/1 : BV photometry of variables in NGC 6397 (Kaluzny, 1997)
J/A+A/425/509 : VI photometry of NGC 6397 (Andreuzzi+, 2004)
J/A+A/503/545 : Equivalent widths of Li, Na, Fe, Ca in NGC 6397 (Lind+, 2009)
J/A+A/505/L13 : Lithium in globular NGC 6397 (Gonzalez Hernandez+, 2009)
Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- Seq Sequential number,
Cl* NGC 6397 KGR NNNNNN in Simbad
7 A1 --- n_Seq [*] * for the targets of Korn et al.
(2007ApJ...671..402K 2007ApJ...671..402K)
9- 10 I2 h RAh Right ascension (J2000)
12- 13 I2 min RAm Right ascension (J2000)
15- 19 F5.2 s RAs Right ascension (J2000)
20 A1 --- --- [0]
22 A1 --- DE- Declination sign (J2000)
23- 24 I2 deg DEd Declination (J2000)
26- 27 I2 arcmin DEm Declination (J2000)
29- 32 F4.1 arcsec DEs Declination (J2000)
33 A1 --- --- [0]
35- 40 F6.3 mag Vmag V magnitude
42- 45 I4 K THa Hα temperature
47- 50 F4.2 [cm/s2] logg Gravity surface
52- 55 F4.2 km/s xi Microturbulent velocity
57- 60 F4.2 [-] log(Mg) Magnesium abundance (1)
62- 65 F4.2 [-] log(Ca) Calcium abundance(1)
67- 70 F4.2 [-] log(Ti) Titanium abundance(1)
72- 75 F4.2 [-] log(Fe) Iron abundance(1)
77- 81 F5.3 mag v-y v-y colour index (Stroemgren)
83- 86 I4 K T(v-y,D) Dwarf temperature from v-y colour index
88- 91 I4 K T(v-y,G) Giant temperature from v-y colour index
93- 97 F5.3 mag V-I V-I colour index
99-102 I4 K T(V-I,D) Dwarf temperature from V-I colour index
104-107 I4 K T(V-I,G) Giant temperature from V-I colour index
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Note (1): abundances ε defined on the scale log(H)=12
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Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- Ion Ion
7- 14 F8.3 0.1nm lambda Wavelength
16- 20 F5.3 eV chi Excitation potential
22- 27 F6.3 [-] loggf Oscillator strength
29- 30 I2 --- r_loggf Reference for loggf (1)
32- 38 F7.3 --- Param ? van der Waals damping data (2)
40- 45 F6.3 [rad/s/cm3] Waals ? van der Waals logarithm of FWHM per unit
perturber number density at 10000K
47- 52 F6.3 [rad/s/cm3] Stark Stark logarithm of FWHM per unit perturber
number density at 10000K
54- 58 F5.3 [rad/s] log(FWHM) Radiative damping data
60- 63 I4 0.1pm dlblue Extent of the spectral windows used for
fitting of each line, blue-wards of the
central wavelength (3)
65- 67 I3 0.1pm dlref Extent of the spectral windows used for
fitting of each line, red-wards of the
central wavelength (3)
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Note (1): References as follows:
1 = Wiese & Martin (1980, NSRDS-NBS, No 68, Part II)
2 = Smith & O'Neill (1975A&A....38....1S 1975A&A....38....1S)
3 = Smith & Raggett (1981, J. Phys. B Atom. Mol. Phys., 14, 4015)
4 = Blackwell et al. (1982MNRAS.201..611B 1982MNRAS.201..611B)
5 = R. Kurucz, http://cfaku5.cfa.harvard.edu/ATOMS/2200
6 = Pickering et al. (2001ApJS..132..403P 2001ApJS..132..403P)
7 = Martin et al. (1988, Phys. Chem. Ref. Data, 17, 3, Cat. VI/72)
8 = R. Kurucz, http://cfaku5.cfa.harvard.edu/ATOMS/2600
9 = O'Brian et al. (1991, J. Opt. Soc. Amer. B Opt. Phys. 8, 1185)
10 = Bard et al. (1991A&A...248..315B 1991A&A...248..315B)
11 = Moity (1983A&AS...52...37M 1983A&AS...52...37M)
12 = Kroll & Kock (1987A&AS...67..225K 1987A&AS...67..225K)
13 = Biemont et al. (1991A&A...249..539B 1991A&A...249..539B)
14 = Schnabel et al. (2004A&A...414.1169S 2004A&A...414.1169S)
15 = Heise & Kock (1990A&A...230..244H 1990A&A...230..244H)
Note (2): van der Waals parameter correspond to the notation of Anstee and
O'Mara (1995MNRAS.276..859A 1995MNRAS.276..859A), where a packed parameter is used for the
broadening cross-section (σ) for collisions by neutral hydrogen
at 10km/s and its velocity dependence (α). E.g. for the MgI
5172.684Å line, Param=729.238 means σ=729 in atomic units
and α=0.238.
Note (3): Zero values in both columns indicate that the line-contribution
is considered in the same window as the one listed directly above.
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History:
From electronic version of the journal
References:
Korn et al., Paper I 2007ApJ...671..402K 2007ApJ...671..402K
(End) Patricia Vannier [CDS] 18-Mar-2010