J/ApJ/905/20 Metal-poor stars observed with SALT/HRS (Rasmussen+, 2020)
Metal-poor stars observed with the Southern African Large Telescope.
Rasmussen K.C., Zepeda J., Beers T.C., Placco V.M., Depagne E., Frebel A.,
Dietz S., Hartwig T.
<Astrophys. J., 905, 20 (2020)>
=2020ApJ...905...20R 2020ApJ...905...20R
ADC_Keywords: Stars, metal-deficient; Spectra, optical; Abundances;
Effective temperatures
Keywords: Stellar nucleosynthesis ; Explosive nucleosynthesis ; Milky Way
stellar halo ; Stellar abundances ; Stellar dynamics
Abstract:
We present the first release of a large-scale study of relatively
bright (V<13.5) metal-poor stars observed with the Southern African
Large Telescope (SALT), based on high-resolution spectra of 50 stars
with a resolving power of R∼40000 and S/N∼20 per pixel at 4300Å.
The elemental abundances of C, Sr, Ba, and Eu are reported, as well as
several α-elements (Mg, Ca, Sc, Ti, and V) and iron-peak
elements (Mn, Co, Ni, and Zn). We find a diverse array of abundance
patterns, including several consistent with the signatures of
carbon-enhanced metal-poor CEMP-i and CEMP-r stars. We find that 15 of
50 (30%) are carbon enhanced (with [C/Fe]>+0.70), and that a large
fraction (26 of 50, 52%) are enhanced in r-process elements. Among the
r-process-enhanced stars, five are strongly enhanced r-II
([Eu/Fe]>+1.0) stars (two of which are newly discovered) and 21 are
newly discovered moderately enhanced r-I (+0.3≤[Eu/Fe]≤+1.0) stars.
There are eight stars in our sample that, on the basis of their
abundances and kinematics, are possible members of the metal-weak
thick-disk population. We also compare our measured abundances to
progenitor-enrichment models, and find that the abundance patterns for
the majority of our stars can be attributed to a single (rather than
multiple) enrichment event.
Description:
The stars that comprise this sample are the first data release from a
total of ∼200 metal-poor stars, selected from candidates identified
during the Radial Velocity Experiment (RAVE) survey
(Kunder+, 2017, III/279).
A total of 55hr of observing time was granted at the 11m Southern
African Large Telescope (SALT) for the Long Term Proposal
2017-1-MLT-012, "Detailed Study of CEMP Stars Identified in the RAVE
Survey." The observations were carried out in service mode during four
consecutive semesters, beginning in 2017 April and ending in 2019
March. A total of 223 stars were observed with the High Resolution
Spectrograph (HRS) at a resolving power of R∼40000. The useful
wavelength range of the spectra is 3990-5560Å.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 132 9 Stellar atmospheric parameters and abundances for
previously observed stars
table4.dat 42 50 Stellar atmospheric parameters for the program stars
table5.dat 100 50 Classification abundances for the program stars
table6.dat 76 50 Abundance ratios for the Elements Mg, Ca, ScII, TiI,
and Ti II
table7.dat 98 50 Abundance ratios for the elements VI, CrI, CrII, Mn,
Co, Ni, and Zn
table8.dat 26 414 Line list for abundances
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See also:
III/272 : RAVE 4th data release (Kordopatis+, 2013)
III/279 : RAVE 5th data release (Kunder+, 2017)
J/AJ/103/1987 : Stars of very low metal abundance (Beers+ 1992)
J/MNRAS/404/1529 : s-process in low-metallicity stars (Bisterzo+, 2010)
J/AJ/141/175 : Abundances in M15 RGB/RHB stars (Sobeck+, 2011)
J/ApJ/769/57 : Equivalent widths of metal-poor stars (Frebel+, 2013)
J/ApJ/797/21 : Carbon-enhanced metal-poor stars (Placco+, 2014)
J/AJ/147/136 : Stars of very low metal abundance. VI. (Roederer+, 2014)
J/ApJ/833/20 : Carbon-enhanced metal-poor star abundances (Yoon+, 2016)
J/ApJ/835/81 : Bright metal-poor stars from HES Survey. II. (Beers+, 2017)
J/A+A/618/A133 : Non standard s-process in rotating stars (Choplin+, 2018)
J/ApJ/858/92 : RPA Southern Pilot Search of 107 Stars (Hansen+, 2018)
J/AJ/155/256 : Spec. validation of RAVE metal-poor stars (Placco+, 2018)
J/ApJ/868/110 : R-Process Alliance: 1st release in Gal. halo (Sakari+, 2018)
J/ApJ/870/122 : Spectroscopy of low-metallicity stars (Placco+, 2019)
J/ApJ/898/150 : High-res. MIKE obs. of metal-poor stars (Ezzeddine+, 2020)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [RAVE]
6- 21 A16 --- RAVE Stellar identifier (JHHMMSS.s+DDMMSS)
23- 38 A16 --- OName Other identifier
40- 40 I1 --- Ref [1/6] Literature Reference (1)
42- 45 I4 K Teff0 [4701/6225] Effective temperature, literature
47- 50 F4.2 [cm/s2] logg0 [1.5/4.6] log surface gravity, literature
52- 56 F5.2 [-] [Fe/H]0 [-3.2/-1.5] metallicity, literature
58- 61 F4.2 km/s vt0 [1.5/3] microturbulent velocity, literature
63- 66 I4 K Teff [4711/6115] Effective temperature, this work
68- 71 F4.2 [cm/s2] logg [1.3/4] log surface gravity, this work
73- 77 F5.2 [-] [Fe/H] [-2.92/-1.8] Metallicity, this work
79- 82 F4.2 km/s vt [1.5/2.7] microturbulent velocity, this work
84- 88 F5.2 [-] [C/Fe]0 [-0.4/1.51] Log C/Fe number abundance ratio,
literature (2)
90- 94 F5.2 [-] [Sr/Fe]0 [-0.33/0.9] Log Sr/Fe number abundance
ratio, literature (2)
96-100 F5.2 [-] [Ba/Fe]0 [-1.36/1.17] Log Ba/Fe number abundance
ratio, literature (2)
102-102 A1 --- l_[Eu/Fe]0 Limit flag on [Eu/Fe]0
103-107 F5.2 [-] [Eu/Fe]0 [-0.21/1.63] Log Eu/Fe number abundance
ratio, literature (2)
109-109 A1 --- l_[C/Fe] Limit flag on [C/Fe]
110-114 F5.2 [-] [C/Fe] [0/1.44] Log C/Fe number abundance ratio,
this work (3)
116-120 F5.2 [-] [Sr/Fe] [-0.3/0.96]? Log Sr/Fe number abundance
ratio, this work
122-126 F5.2 [-] [Ba/Fe] [-1.23/1.2] Log Ba/Fe number abundance
ratio, this work
128-132 F5.2 [-] [Eu/Fe] [0.18/1.8]? Log Eu/Fe number abundance
ratio, this work
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Note (1): Literature citations are as follows:
1 = Hill et al. (2002A&A...387..560H 2002A&A...387..560H);
2 = Hansen et al. (2015ApJ...807..173H 2015ApJ...807..173H);
3 = Sakari et al. (2018ApJ...854L..20S 2018ApJ...854L..20S);
4 = Sakari et al. (2018, J/ApJ/868/110);
5 = Hansen et al. (2018, J/ApJ/858/92)
6 = Roederer et al. (2014, J/AJ/147/136).
Note (2): Average Uncertainties for [X/Fe] measurements are:
Hill et al. (2002A&A...387..560H 2002A&A...387..560H): ∼0.05-0.2dex;
Hansen et al. (2015ApJ...807..173H 2015ApJ...807..173H): ∼0.2-0.3dex;
Sakari et al. (2018, J/ApJ/868/110): ∼0.05-0.2dex;
Sakari et al. (2018ApJ...854L..20S 2018ApJ...854L..20S): ∼0.1-0.2dex;
Hansen et al. (2018, J/ApJ/858/92): ∼0.3-0.4dex;
Roederer et al. (2014, J/AJ/147/136): ∼0.2-0.3dex.
Note (3): The [C/Fe] value reported is "as measured"", not corrected for
evolutionary effects, as in the rest of the paper.
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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- 4 A4 --- --- [RAVE]
6- 21 A16 --- RAVE Stellar identifier (JHHMMSS.s+DDMMSS)
23- 26 I4 K Teff [4360/6115] Effective temperature
28- 31 F4.2 [cm/s2] logg [0.6/4.25] log of surface gravity
33- 37 F5.2 [-] [Fe/H] [-2.92/-0.94] Metallicity
39- 42 F4.2 km/s vt [1.25/3.3] Microturbulent velocity
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Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [RAVE]
6- 21 A16 --- RAVE Stellar identifier (JHHMMSS.s+DDMMSS)
23- 29 A7 --- Class Class (1)
31- 31 A1 --- l_ACcorr Limit flag on ACcorr
34- 37 F4.2 --- ACcorr [5.92/8.1] Corrected absolute carbon
abundance A(C)=log(NC/NH)+12
39- 39 A1 --- l_[C/Fe] Limit flag on [C/Fe]
41- 45 F5.2 [-] [C/Fe] [-0.48/1.44] Log C/Fe number abundance ratio
47- 50 F4.2 [-] e_[C/Fe] [0.25/0.25]? Uncertainty in [C/Fe]
52- 52 A1 --- l_[C/Fe]corr Limit flag on [C/Fe]corr
55- 59 F5.2 [-] [C/Fe]corr [0.06/1.58]? Corrected, [C/Fe] (2)
61- 64 F4.2 [-] e_[C/Fe]corr [0.2/0.3]? Uncertainty in [C/Fe]corr
66- 70 F5.2 [-] [Sr/Fe] [-1.73/1.24]? Log Sr/Fe number abundance ratio
72- 75 F4.2 [-] e_[Sr/Fe] [0.1/0.5]? Uncertainty in [Sr/Fe]
77- 81 F5.2 [-] [Ba/Fe] [-1.6/1.52]? Log Ba/Fe number abundance ratio
83- 86 F4.2 [-] e_[Ba/Fe] [0.1/0.3]? Uncertainty in [Ba/Fe]
88- 88 A1 --- l_[Eu/Fe] Limit flag on [Eu/Fe]
91- 95 F5.2 [-] [Eu/Fe] [-0.04/1.8]? Log Eu/Fe number abundance ratio
97-100 F4.2 [-] e_[Eu/Fe] [0.2/0.3]? Uncertainty in [Eu/Fe]
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Note (1): Carbon-enhanced metal-poor (CEMP) and r-process-enhanced star subclass
as follows:
CEMP-i = [C/Fe]>+0.7, 0.0<[Ba/Eu]<+0.5 (-1.0<[Ba/Pb]<-0.5)
CEMP-no = [C/Fe]≥+0.7 and [Ba/Fe]≤0.0, or a published light-element
enrichment pattern that clearly suggests CEMP-no status;
CEMP-r = [C/Fe]≥+0.7 and [Eu/Fe]>+1.0,
CEMP-s = [C/Fe]>+0.7, [Ba/Fe]>+1.0, [Ba/Eu]>+0.5
r-I = 0.3≤[Eu/Fe]≤+1.0, [Ba/Eu]<0
r-II = [Eu/Fe]>+1.0, [Ba/Eu]<0
Note (2): Values of [C/Fe] corrected for evolutionary effects, as discussed by
Placco+ (2014, J/ApJ/797/21).
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [RAVE]
6- 21 A16 --- RAVE Stellar identifier (JHHMMSS.s+DDMMSS)
23- 27 F5.2 [-] [Mg/Fe] [0.19/0.61]? Log Mg/Fe number abundance ratio
29- 32 F4.2 [-] e_[Mg/Fe] [0.01/0.2]? Uncertainty in [Mg/Fe] (1)
34- 38 F5.2 [-] [Ca/Fe] [0.22/0.81]? Log Ca/Fe number abundance ratio
40- 43 F4.2 [-] e_[Ca/Fe] [0.01/0.25]? Uncertainty in [Ca/Fe] (1)
45- 49 F5.2 [-] [ScII/Fe] [-0.2/0.5] Log ScII/Fe number abundance ratio
51- 54 F4.2 [-] e_[ScII/Fe] [0.01/0.35] Uncertainty in [ScII/Fe] (1)
56- 60 F5.2 [-] [TiI/Fe] [0.02/0.51] Log TiI/Fe number abundance ratio
62- 65 F4.2 [-] e_[TiI/Fe] [0.04/0.2] Uncertainty in [TiI/Fe] (1)
67- 71 F5.2 [-] [TiII/Fe] [0.12/0.6] Log TiII/Fe number abundance ratio
73- 76 F4.2 [-] e_[TiII/Fe] [0.05/0.2] Uncertainty in [TiII/Fe] (1)
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Note (1): Uncertainties are taken as the standard deviation of multiple
measurements; in cases uncertainty of 0.10dex has been assigned.
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [RAVE]
6- 21 A16 --- RAVE Stellar identifier (JHHMMSS.s+DDMMSS)
23- 27 F5.2 [-] [VI/Fe] [-0.27/0.5]? Log VI/Fe number abundance ratio
29- 32 F4.2 [-] e_[VI/Fe] [0.1/0.1]? Uncertainty in [VI/Fe] (1)
34- 38 F5.2 [-] [CrI/Fe] [-0.4/0.08] Log CrI/Fe number abundance ratio
40- 43 F4.2 [-] e_[CrI/Fe] [0.02/0.21] Uncertainty in [CrI/Fe] (1)
45- 49 F5.2 [-] [CrII/Fe] [-0.2/0.33]? Log CrII/Fe number abundance
ratio
51- 54 F4.2 [-] e_[CrII/Fe] [0.01/0.1]? Uncertainty in [CrII/Fe] (1)
56- 60 F5.2 [-] [Mn/Fe] [-0.6/0.2]? Log Mn/Fe number abundance ratio
62- 65 F4.2 [-] e_[Mn/Fe] [0.01/0.32]? Uncertainty in [Mn/Fe] (1)
67- 71 F5.2 [-] [Co/Fe] [-0.12/0.8]? Log Co/Fe number abundance ratio
73- 76 F4.2 [-] e_[Co/Fe] [0.01/0.22]? Uncertainty in [Co/Fe] (1)
78- 82 F5.2 [-] [Ni/Fe] [-0.14/0.25] Log Ni/Fe number abundance ratio
84- 87 F4.2 [-] e_[Ni/Fe] [0.02/0.16] Uncertainty in [Ni/Fe] (1)
89- 93 F5.2 [-] [Zn/Fe] [-0.16/0.5]? Log Zn/Fe number abundance ratio
95- 98 F4.2 [-] e_[Zn/Fe] [0.01/0.13]? Uncertainty in [Zn/Fe] (1)
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Note (1): Uncertainties are taken as the standard deviation of multiple
measurements; in cases uncertainty of 0.10dex has been assigned.
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Byte-by-byte Description of file: table8.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Ion Species
7- 14 F8.3 0.1nm lambda [3578.68/6297.792] Wavelength, Angstroms
16- 19 F4.2 eV ExPot [0.0/4.55] Excitation potential
21- 26 F6.3 [-] loggf [-5.7/0.65] log, statistical weight*oscillator
strength
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 25-Apr-2022