J/A+A/534/A123 Horizontal branch stars in NGC 2808 (Gratton+, 2011)
The Na-O anticorrelation in horizontal branch stars. I. NGC 2808.
Gratton R.G., Lucatello S., Carretta E., Bragaglia A., D'Orazi V.,
Al Momany Y.
<Astron. Astrophys., 534, A123 (2011)>
=2011A&A...534A.123G 2011A&A...534A.123G
ADC_Keywords: Clusters, globular ; Stars, horizontal branch ; Spectroscopy
Keywords: stars: evolution - stars: abundances - stars: Population II -
globular clusters: general
Abstract:
Globular clusters have been recognized to host multiple stellar
populations. A spectacular example of this is the massive cluster NGC
2808, where multiple populations have been found along the horizontal
branch (HB) and the main sequence (MS). Studies of red giants showed
that this cluster appears homogeneous insofar Fe abundance is
concerned, but it shows an extended anticorrelation between Na and O
abundances. The Na-poor, O-rich population can be identified with the
red MS, and the Na-rich, O-poor one with the blue one. This may be
understood in terms of different He content, He being correlated with
Na. A prediction of this scenario is that He-rich, Na-rich He-core
burning stars, because they are less massive, will end up on the bluer
part of the HB, while He-poor, Na-poor stars will reside on the red
HB. The aim of this paper is to verify this prediction. To this
purpose, we acquired high-resolution spectra of regions including
strong O and Na lines in several tens of HB stars of NGC 2808,
sampling both the red and blue parts of the HB.
Description:
We used the high multiplex capability of GIRAFFE at VLT to acquire
spectra for 49 stars along the red HB (RHB) and 36 on the blue HB
(BHB) of NGC 2808.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 88 119 Basic data for program stars
table2.dat 93 42 Atmospheric parameters and abundances
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See also:
J/A+A/391/945 : HST photometry of 74 galactic globular clusters (Piotto+, 2002)
J/A+A/549/A41 : Horizontal branch stars in 47 Tuc and M5 (Gratton+, 2013)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Type Type of source (Blue HB, Red HB or Lower RGB)
11- 15 I5 --- Star Star identification number,
<Cl* NGC 2808 PKD NNNNN> in Simbad
17 I1 h RAh Right ascension (J2000)
19- 20 I2 min RAm Right ascension (J2000)
22- 27 F6.3 s RAs Right ascension (J2000)
29 A1 --- DE- Declination sign (J2000)
30- 31 I2 deg DEd Declination (J2000)
33- 34 I2 arcmin DEm Declination (J2000)
36- 40 F5.2 arcsec DEs Declination (J2000)
42- 47 F6.3 mag Bmag B magnitude
49- 54 F6.3 mag Vmag V magnitude
56- 61 F6.3 mag Kmag ? 2MASS Ks magnitude
63- 67 F5.1 km/s RV ? Radial velocity
69- 72 F4.1 --- S/N1 ? HR12 grating signal-to-noise ratio
74- 77 F4.1 --- S/N2 ? HR19 grating signal-to-noise ratio
79- 88 A10 --- Note Membership note
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 A9 --- Type Type of source (Blue HB, Ref HB or Lower RGB)
11- 15 I5 --- Star Star identification number
17- 21 I5 K Teff Effective temperature
23- 26 F4.2 [cm/s2] logg Surface gravity
28- 29 I2 --- o_[FeI/H] ? Number of lines for [FeI/H]
31- 35 F5.2 [Sun] [FeI/H] ? Abundance [FeI/H]
37- 40 F4.2 [Sun] e_[FeI/H] ? rms uncertainty on [FeI/H]
42- 46 F5.2 [Sun] [FeII/H] ? Abundance [FeII/H]
48 I1 --- o_[O/Fe] ? Number of lines for [O/Fe]
50- 54 F5.2 [Sun] [O/Fe] ? Abundance [OI/Fe]
56- 59 F4.2 [Sun] e_[O/Fe] ? rms uncertainty on [O/Fe]
61 I1 --- o_[Na/Fe] Number of lines for [Na/Fe]
63- 67 F5.2 [Sun] [Na/Fe] Abundance [NaI/Fe]
69- 72 F4.2 [Sun] e_[Na/Fe] ? rms uncertainty on [Na/Fe]
74- 77 F4.2 [Sun] [Mg/Fe] ? Abundance [MgI/Fe]
79- 82 F4.2 [Sun] [Si/Fe] ? Abundance [SiI/Fe]
84- 87 F4.2 [Sun] [Ca/Fe] ? Abundance [CaI/Fe]
89- 93 F5.2 [Sun] [Ba/Fe] ? Abundance [BaII/Fe]
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History:
From electronic version of the journal
References:
Gratton et al., Paper II 2012A&A...539A..19G 2012A&A...539A..19G, Cat. J/A+A/539/A19
Gratton et al., Paper III 2012A&A...549A..41G 2012A&A...549A..41G, Cat. J/A+A/549/A41
(End) Patricia Vannier [CDS] 30-Jan-2012