J/MNRAS/437/1609 NGC 2808 HB stars abundances (Marino+, 2014)
Helium enhanced stars and multiple populations along the horizontal branch of
NGC 2808: direct spectroscopic measurements.
Marino A.F., Milone A.P., Przybilla N., Bergemann M., Lind K., Asplund M.,
Cassisi S., Catelan M., Casagrande L., Valcarce A.A.R., Bedin L.R.,
Cortes C., D'antona F., Jerjen H., Piotto G., Schlesinger K., Zoccali M.,
Angeloni R.
<Mon. Not. R. Astron. Soc., 437, 1609-1627 (2014)>
=2014MNRAS.437.1609M 2014MNRAS.437.1609M
ADC_Keywords: Clusters, globular ; Stars, horizontal branch ; Abundances
Keywords: techniques: spectroscopic - stars: abundances - stars: Population II -
globular clusters: general - globular clusters: individual: NGC 2808
Abstract:
We present an abundance analysis of 96 horizontal branch (HB) stars in
NGC 2808, a globular cluster exhibiting a complex multiple stellar
population pattern. These stars are distributed in different portions
of the HB and cover a wide range of temperature. By studying the
chemical abundances of this sample, we explore the connection between
HB morphology and the chemical enrichment history of multiple stellar
populations. For stars lying on the red HB, we use GIRAFFE and UVES
spectra to determine Na, Mg, Si, Ca, Sc, Ti, Cr, Mn, Fe, Ni, Zn, Y, Ba
and Nd abundances. For colder, blue HB stars, we derive abundances for
Na, primarily from GIRAFFE spectra. We were also able to measure
direct non-local thermodynamic equilibrium He abundances for a subset
of these blue HB stars with temperature higher than ∼9000K. Our
results show that: (i) HB stars in NGC 2808 show different content in
Na depending on their position in the colour-magnitude diagram, with
blue HB stars having higher Na than red HB stars; (ii) the red HB is
not consistent with a uniform chemical abundance, with slightly warmer
stars exhibiting a statistically significant higher Na content; and
(iii) our subsample of blue HB stars with He abundances shows evidence
of enhancement with respect to the predicted primordial He content by
ΔY=+0.09±0.01±0.05 (internal plus systematic uncertainty).
Our results strongly support theoretical models that predict He
enhancement among second-generation(s) stars in globular clusters and
provide observational constraints on the second-parameter governing HB
morphology.
Description:
To identify our stellar sample, we use the photometric catalogue of
Momany et al. (2004), which has been obtained from U, B and V images
collected with the Wide-Field Imager (WFI) mounted at the 2.2m ESO-MPI
(Max-Planck-Institut) telescope at La Silla observatory, Chile.
Our spectroscopic data consist of FLAMES/GIRAFFE and FLAMES/UVES data
collected under the ESO programme 086.D-0141 (PI: Marino). The GIRAFFE
fibres were used with the HR12 setup, covering the spectral range from
∼5820 to ∼6140Å with a resolution of ∼18700.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 86 108 *Basic data for the analysed UVES and GIRAFFE stars
table2.dat 25 3 Atmospheric parameters from Fe lines, and Teff from
photometry for the RHB stars observed with UVES
table3.dat 86 68 Atmospheric parameters and chemical abundances for
the RHB stars and colder BHB stars observed with
GIRAFFE
table4.dat 207 3 Atmospheric parameters and individual abundances,
with the associated line-to-line scatter,
for the RHB stars observed with UVES
table6.dat 48 4 Atmospheric parameters, chemical abundances and
line-to-line scatter (when applicable) for the
BHB UVES stars
table7.dat 56 21 Atmospheric parameters, EWs for the He line and
He mass fractions for the BHB stars observed with
GIRAFFE
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Note on table1.dat: Identification numbers and photometric data are from
Momany et al. (2004A&A...420..605M 2004A&A...420..605M).
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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/A+A/417/597 : Radial velocities in 4 globular clusters (Recio-Blanco+, 2004)
J/ApJ/625/156 : FUV-NUV observations of NGC 2808 (Dieball+, 2005)
J/AJ/131/1766 : Abundances and equivalent widths in NGC 2808 (Carretta, 2006)
J/A+A/480/397 : XMM observations of NGC 2808 and NGC 4372 (Servillat+, 2008)
J/A+A/490/641 : X-ray sources toward NGC 2808 (Servillat+, 2008)
J/A+A/528/A127 : Radial velocities in the globular NGC 2808 (Moni Bidin+, 2011)
J/A+A/534/A123 : Horizontal branch stars in NGC 2808 (Gratton+, 2011)
J/A+A/542/A129 : NGC 2808 central kinematics (Luetzgendorf+, 2012)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Inst Instrument (GIRAFFE or UVES)
9- 13 I5 --- ID [231/23610] Star ID number
15- 16 I2 h RAh Right ascension (J2000)
18- 19 I2 min RAm Right ascension (J2000)
21- 26 F6.3 s RAs Right ascension (J2000)
28 A1 --- DE- Declination sign (J2000)
29- 30 I2 deg DEd Declination (J2000)
32- 33 I2 arcmin DEm Declination (J2000)
35- 40 F6.3 arcsec DEs Declination (J2000)
42- 47 F6.3 mag Vmag V magnitude
49- 53 F5.3 mag B-Vo Original B-V colour index
55- 59 F5.3 mag B-Vc Corrected B-V colour index
61- 65 F5.1 km/s RV [-15/124] Radial velocity
67- 82 A16 --- 2MASS 2MASS identification (HHMMSSss+DDMMSSs)
84- 86 A3 --- Type Star type (BHB, RHB, F or GJ) (1)
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Note (1): the types are!
BHB = Blue Horizontal Branch
RHB = Red Horizontal Branch
F = field star
GJ = Grundahl Jump (levitation of metals and sedimentation of He; see
Grundahl et al. 1999ApJ...524..242G 1999ApJ...524..242G
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- ID [231/23610] Star Identification number
7- 10 I4 K Teff Effective temperature from Fe line
12- 15 F4.2 [cm/s2] logg Surface gravity from Fe line
17- 20 F4.2 km/s vt Microturbulent velocity from Fe line
22- 25 I4 K TeffA Effective temperature from photometry (Alonso)
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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- 5 I5 --- ID [231/23610] Star Identification number
7- 10 I4 K Teff Effective temperature
12- 15 F4.2 [cm/s2] logg surface gravity
17- 20 F4.2 km/s vt Microturbulent velocity
22- 26 F5.2 [Sun] [Fe/H]1 ?=- Abundance [Fe/H] from FeI
28- 32 F5.2 [Sun] [Fe/H]2 ?=- Abundance [Fe/H] from FeII
34- 37 F4.2 [Sun] [Na/Fe] LTE abundance [Na/Fe]
39- 43 F5.2 [Sun] [Na/Fe]n NLTE abundance [Na/Fe]
45- 48 F4.2 [Sun] e_[Na/Fe] ?=- rms uncertainty on abundances [Na/Fe]
50- 53 F4.2 [Sun] [Si/Fe] ?=- Abundance [Si/Fe]
55- 58 F4.2 [Sun] [Ca/Fe] ?=- Abundance [Ca/Fe]
60- 64 F5.2 [Sun] [Ti/Fe] ?=- Abundance [Ti/Fe]
66- 70 F5.2 [Sun] [Mn/Fe] ?=- Abundance [Mn/Fe]
72- 75 F4.2 [Sun] e_[Mn/Fe] ?=- rms uncertainty on abundance [Mn/Fe]
77- 81 F5.2 [Sun] [Ba/Fe] ?=- Abundance [Ba/Fe]
83- 86 I4 K TeffI ?=- effective temperature from IRFM
(Infra-Red Flux Method)
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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- 5 I5 --- ID [231/23610] Star Identification number
7- 10 I4 K Teff Effective temperature
12- 15 F4.2 [cm/s2] logg Surface gravity
17- 20 F4.2 km/s vt Microturbulent velocity
22- 26 F5.2 [Sun] [Fe/H] Abundance [Fe/H]
28- 32 F5.2 [Sun] [Fe/H]1 Abundance [Fe/H]I
34- 37 F4.2 [Sun] e_[Fe/H]1 rms uncertainty in abundance [Fe/H]I
39- 43 F5.2 [Sun] [Fe/H]2 Abundace [Fe/H]II
45- 48 F4.2 [Sun] e_[Fe/H]2 rms uncertainty in abundance [Fe/H]II
50- 53 F4.2 [Sun] [Na/Fe] LTE abundance [Na/Fe]
55- 58 F4.2 [Sun] e_[Na/Fe] rms uncertainty on abundance [Na/Fe]LTE
60- 64 F5.2 [Sun] [Na/Fe]n NLTE abundance [Na/Fe]
66- 69 F4.2 [Sun] e_[Na/Fe]n rms uncertainty on abundance [Na/Fe]NLTE
71- 74 F4.2 [Sun] [Mg/Fe] Abundance [Mg/Fe]
76- 79 F4.2 [Sun] e_[Mg/Fe] rms uncertainty on abundance [Mg/Fe]
81- 84 F4.2 [Sun] [Si/Fe] Abundance [Si/Fe]
86- 89 F4.2 [Sun] e_[Si/Fe] rms uncertainty on abundance [Si/Fe]
91- 94 F4.2 [Sun] [Ca/Fe] Abundance [Ca/Fe]
96- 99 F4.2 [Sun] e_[Ca/Fe] rms uncertainty on abundance [Ca/Fe]
101-105 F5.2 [Sun] [Sc/Fe] Abundance [Ti/Fe]
107-110 F4.2 [Sun] e_[Sc/Fe] rms uncertainty on abundance [Sc/Fe]
112-115 F4.2 [Sun] [Ti/Fe]1 Abundance [Ti/Fe]I
117-120 F4.2 [Sun] e_[Ti/Fe]1 rms uncertainty on abundance [Ti/Fe]I
122-125 F4.2 [Sun] [Ti/Fe]2 Abundance [Ti/Fe]II
127-130 F4.2 [Sun] e_[Ti/Fe]2 rms uncertainty on abundance [Ti/Fe]II
132-136 F5.2 [Sun] [Cr/Fe]1 Abundance [Mn/Fe]I
138-141 F4.2 [Sun] e_[Cr/Fe]1 rms uncertainty on abundance [Cr/Fe]I
143-147 F5.2 [Sun] [Cr/Fe]2 Abundance [Mn/Fe]II
149-152 F4.2 [Sun] e_[Cr/Fe]2 rms uncertainty on abundance [Cr/Fe]II
154-158 F5.2 [Sun] [Ni/Fe] Abundance [Ni/Fe]
160-163 F4.2 [Sun] e_[Ni/Fe] rms uncertainty on abundance [Ni/Fe]
165-169 F5.2 [Sun] [Zn/Fe] Abundance [Zn/Fe]
171-174 F4.2 [Sun] e_[Zn/Fe] rms uncertainty on abundance [Zn/Fe]
176-180 F5.2 [Sun] [Y/Fe] Abundance [Y/Fe]
182-185 F4.2 [Sun] e_[Y/Fe] rms uncertainty on abundance [Y/Fe]
187-191 F5.2 [Sun] [Ba/Fe]2 Abundance [Ba/Fe]II
193-196 F4.2 [Sun] e_[Ba/Fe]2 rms uncertainty on abundance [Ba/Fe]II
198-202 F5.2 [Sun] [Nd/Fe]2 Abundance [Nd/Fe]II
204-207 F4.2 [Sun] e_[Nd/Fe]2 rms uncertainty on abundance [Nd/Fe]II
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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- 5 I5 --- ID ID number
7- 11 I5 K Teff Effective temperature
13- 16 F4.2 [cm/s2] logg Surface gravity
18- 21 F4.2 km/s vt Microturbulent velocity
23- 27 F5.2 [Sun] [Fe/H]2 Abundance [Fe/H]
29- 32 F4.2 [Sun] e_[Fe/H]2 rms uncertainty on abundance [Fe/H]
34 A1 --- l_[Na/Fe]n Limit flag on [Na/Fe]NLTE
35- 38 F4.2 [Sun] [Na/Fe]n Abundance [Na/Fe]NLTE
40- 43 F4.2 [Sun] [Mg/Fe] Abundance [Mg/Fe]
45- 48 F4.2 [Sun] e_[Mg/Fe] rms uncertainty on abundance [Mg/Fe]
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Type Star type
10- 14 I5 --- ID ID number
16- 20 I5 K Teff Effective temperature
22- 25 F4.2 [cm/s2] logg Surface gravity
27- 30 F4.2 km/s vt Microturbulent velocity
32- 36 F5.1 0.1pm EW He equivalent widths (in mÅ)
38- 39 I2 km/s vsini [0/15] Rotational velocity
41- 45 F5.3 --- Y [0.03/0.45] NLTE Y mass fraction
47- 51 I5 K TeffH ? HST effective temperature
53- 56 F4.2 [cm/s2] loggH ? HST surface gravity
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 19-Nov-2014