J/A+A/592/A66 NGC 2808 AGB and RGB stars Na abundance (Wang+, 2016)
Sodium abundances of AGB and RGB stars in Galactic globular clusters.
I. Analysis and results of NGC 2808.
Wang Y., Primas F., Charbonnel C., Van der Swaelmen M., Bono G.,
Chantereau W., Zhao G.
<Astron. Astrophys. 592, A66 (2016)>
=2016A&A...592A..66W 2016A&A...592A..66W (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Stars, giant ; Abundances ; Photometry ;
Radial velocities
Keywords: stars: abundances - globular clusters: general -
globular clusters: individual: NGC 2808
Abstract:
Galactic globular clusters (GC) are known to have multiple stellar
populations and be characterised by similar chemical features, e.g.,
O-Na anti-correlation. While second-population stars, identified by
their Na overabundance, have been found from the main sequence turnoff
up to the tip of the red giant branch in various Galactic GCs,
asymptotic giant branch stars have rarely been targeted. Here we
present the results of our high-resolution spectroscopic study of a
sample of AGB and RGB stars in the Galactic globular cluster NGC 2808.
We derived accurate Na abundances for 31 AGB and 40 RGB stars in this
cluster. Comparable Na abundance dispersions are found for our AGB and
RGB samples, and we conclude that NGC 2808 has Na-rich
second-population AGB stars, which turn out to be even more numerous
- in relative terms - than their Na-poor counterparts (on the AGB) and
the Na-rich stars on the RGB.
Description:
The high-resolution spectra of our sample of AGB and RGB stars in the
Galactic globular cluster NGC 2808 were obtained with the
high-resolution multi-object spectrograph FLAMES, mounted on
ESO/VLT-UT2. A combined mode was used where the brightest five objects
was observed with UVES-fibre and the remaining targets with
GIRAFFE/Medusa. The basic information of our sample stars are listed
in Table 2, including the evolutionary phase, instrument used for
observation, coordinates, photometry and barycentric radial velocity.
Our Fe abundances were derived from the equivalent widths of Fe lines,
while the Na abundances were determined with spectra synthesis.
Both FeI and Na abundances have been corrected for the non-LTE effect.
In Table 4 we show the derived stellar parameters of our sample stars,
and the Na abundances are shown in Table 6.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 134 73 Basic information of our sample stars
table4.dat 64 73 Stellar parameters of our sample stars
table6.dat 63 73 Na abundances of our sample stars
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See also:
J/A+AS/84/59 : Photometry of NGC 2808 (Ferraro+, 1990)
J/ApJ/562/368 : UV photometry in NGC 2808 (Brown+, 2001)
J/A+A/413/343 : RGB stars in NGC 2808 (Cacciari+, 2004)
J/ApJ/625/156 : FUV-NUV observations of NGC 2808 (Dieball+, 2005)
J/AJ/131/1766 : Abundances & equivalent widths in NGC 2808 (Carretta, 2006)
J/A+A/490/641 : X-ray sources toward NGC 2808 (Servillat+, 2008)
J/A+A/534/A123 : Horizontal branch stars in NGC 2808 (Gratton+, 2011)
J/A+A/542/A129 : NGC 2808 central kinematics (Luetzgendorf+, 2012)
J/MNRAS/437/1609 : NGC 2808 HB stars abundances (Marino+, 2014)
J/ApJ/810/148 : Red giant abundances in NGC 2808 (Carretta, 2015)
J/A+A/586/A51 : JK photometry of NGC 2808 (Massari+, 2016)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- StarID Star identification (1)
11- 13 A3 --- EvolPh [AGB RGB] Evolutionary phase
15- 21 A7 --- Inst Instrument used to obtain the spectrum
23- 24 I2 h RAh Right Ascension (J2000)
26- 27 I2 min RAm Right Ascension (J2000)
29- 33 F5.2 s RAs Right Ascension (J2000)
35 A1 --- DE- Declination sign (J2000)
36- 37 I2 deg DEd Declination (J2000)
39- 40 I2 arcmin DEm Declination (J2000)
42- 46 F5.2 arcsec DEs Declination (J2000)
48- 53 F6.3 mag Bmag Apparent Johnson-Morgan B magnitude (2)
55- 60 F6.4 mag e_Bmag Error of B magnitude (2)
62- 67 F6.3 mag Vmag Apparent Johnson-Morgan V magnitude (2)
69- 74 F6.4 mag e_Vmag Error of V magnitude (2)
76- 81 F6.3 mag Imag Apparent Johnson-Morgan I magnitude (2)
83- 88 F6.4 mag e_Imag Error of I magnitude (2)
90- 95 F6.3 mag Jmag ? 2MASS J magnitude (3)
97-101 F5.3 mag e_Jmag ? Error of J magnitude (3)
103-108 F6.3 mag Hmag ? 2MASS H magnitude (3)
110-114 F5.3 mag e_Hmag ? Error of H magnitude (3)
116-121 F6.3 mag Kmag ? 2MASS K magnitude (3)
123-127 F5.3 mag e_Kmag ? Error of K magnitude (3)
129-134 F6.2 km/s RV Barycentric radial velocity
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Note (1): The 'StarID' reports the original ID from the photometric catalogue,
to which we added the suffix AGB/RGB to ease our own data handling.
Note (2): The optical photometry (B, V and I) were obtained from the
Johnson-Morgan photometric database which is part of the project described in
Stetson (2000PASP..112..925S 2000PASP..112..925S, 2005PASP..117.1325S 2005PASP..117.1325S).
Note (3): The infrared J, H and K magnitudes were obtained from the 2MASS
catalogue (Skrutskie et al., 2006, Cat. VII/233) by coordinates cross-matching.
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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- 9 A9 --- StarID Star identification
11- 13 A3 --- EvolPh [AGB RGB] Evolutionary phase
15- 21 A7 --- Inst Instrument used to obtain the spectrum
23- 26 I4 K Teff Effective temperature
28- 31 F4.2 [cm/s2] logg Surface gravity
33- 36 F4.2 km/s Vturb Microturbulence velocity
38- 42 F5.2 [-] [FeI/H]LTE LTE line ratio [FeI/H]
44- 47 F4.2 [-] s_FeIline Abundance dispersion of FeI lines
49- 53 F5.2 [-] [FeII/H] Line ratio [FeII/H]
55- 58 F4.2 [-] s_FeIIline Abundance dispersion of FeII lines
60- 64 F5.2 [-] [FeI/H]NLTE NLTE line ratio [FeI/H]
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- StarID Star identification
11- 13 A3 --- EvolPh [AGB RGB] Evolutionary phase
15- 21 A7 --- Inst Instrument used to obtain the spectrum
23- 27 F5.2 [-] [Na/H]6154LTE ? LTE [Na/H] from 6154A Na line (1)
29- 33 F5.2 [-] [Na/H]6154NLTE ? NLTE [Na/H] from 6154A Na line (1)
35- 39 F5.2 [-] [Na/H]6160LTE ? LTE [Na/H] from 6160A Na line (1)
41- 45 F5.2 [-] [Na/H]6160NLTE ? NLTE [Na/H] from 6160A Na line (1)
47- 51 F5.2 [-] [Na/H]LTE ? Average LTE [Na/H] (1)
53- 57 F5.2 [-] [Na/H]NLTE ? Average NLTE [Na/H] (1)
59- 63 F5.2 [-] [Na/FeI]NLTE ? Average NLTE [Na/FeI] (1)
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Note (1): The abundance value is left blank for the stars whose Na line/lines
are of poor quality or saturate, and no reliable abundance could be derived.
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Acknowledgements:
Yue Wang, ywang(at)nao.cas.cn
(End) Yue Wang [ESO, Germany], Patricia Vannier [CDS] 24-May-2016