J/ApJ/837/176 Spectroscopic obs. of 2 red giant stars in omega Cen (Yong+, 2017)
A chemical signature from fast-rotating low-metallicity massive stars:
ROA 276 in ω Centauri.
Yong D., Norris J.E., Da Costa G.S., Stanford L.M., Karakas A.I.,
Shingles L.J., Hirschi R., Pignatari M.
<Astrophys. J., 837, 176-176 (2017)>
=2017ApJ...837..176Y 2017ApJ...837..176Y (SIMBAD/NED BibCode)
ADC_Keywords: Stars, giant ; Abundances, [Fe/H] ; Equivalent widths ;
Clusters, globular
Keywords: globular clusters: individual: omega Centauri;
stars: abundances; stars: Population II
Abstract:
We present a chemical abundance analysis of a metal-poor star, ROA276,
in the stellar system ω Centauri. We confirm that this star has
an unusually high [Sr/Ba] abundance ratio. Additionally, ROA 276
exhibits remarkably high abundance ratios, [X/Fe], for all elements
from Cu to Mo along with normal abundance ratios for the elements from
Ba to Pb. The chemical abundance pattern of ROA 276, relative to a
primordial ω Cen star ROA 46, is best fit by a fast-rotating
low-metallicity massive stellar model of 20M☉, [Fe/H]=-1.8, and
an initial rotation 0.4 times the critical value; no other
nucleosynthetic source can match the neutron-capture element
distribution. ROA 276 arguably offers the most definitive proof to
date that fast-rotating massive stars contributed to the production of
heavy elements in the early universe.
Description:
We obtained a high-resolution optical spectrum for the red giant
ROA276 and a comparison red giant star ROA46 (V=11.54) using the
Magellan Inamori Kyocera Echelle spectrograph at the 6.5m Magellan
Clay Telescope on 2007 June 22-23. Both stars have proper motions and
radial velocities consistent with cluster membership. The total
exposure time was 10 minutes per target (spectral resolution of
R=56000 and R=44000 in the blue and red arms, respectively).
Objects:
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RA (ICRS) DE Designation(s)
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13 26 47.28 -47 28 46.1 ω Centauri = * ome Cen
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 37 2 Stellar parameters for the program stars
table2.dat 56 333 Line list, equivalent widths, and abundances
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See also:
VII/195 : Globular Clusters in the Milky Way (Harris, 1996)
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
J/A+A/404/187 : Equivalent widths for metal-poor stars (Gratton+, 2003)
J/ApJ/645/613 : Abundances of HD 221170 (Ivans+, 2006)
J/ApJS/162/227 : Transition probabilities for SmII (Lawler+, 2006)
J/A+A/493/959 : UBV(RI)cHalpha photometry in omega Cen (Bellini+, 2009)
J/ApJS/182/51 : Transition proba. of rare earth elements (Lawler+, 2009)
J/MNRAS/403/1413 : Updated stellar yields from AGB models (Karakas, 2010)
J/ApJ/742/37 : Abundances of six RGB stars in M22 (Roederer+, 2011)
J/AJ/141/175 : Abundances in M15 RGB/RHB stars (Sobeck+, 2011)
J/ApJ/750/76 : R-process peaks elements in HD 160617 (Roederer+, 2012)
J/ApJ/797/44 : Evolution and nucleosynthesis of AGB stars (Fishlock+, 2014)
J/A+A/571/A47 : Extensive linelist of CH in stellar atm. (Masseron+, 2014)
J/A+A/574/A129 : The First CEMP star in the Sculptor dSph (Skuladottir+, 2015)
J/ApJS/225/24 : NuGrid stellar data set I. Yields (Pignatari+, 2016)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- --- [ROA]
5- 7 I3 --- ID Red giant star identifier
9-12 I4 K Teff [4075/4125] Spectroscopic effective temperature (1)
14-16 F3.1 [cm/s2] logg [0.2/0.7] Spectroscopic surface gravity (1)
18-21 F4.2 km/s xi [1.7/2.4] Microturbulent velocity (1)
23-27 F5.2 [Sun] [Fe/H] [-1.8/-1.3] Spectroscopic [Fe/H] abundance
29-32 I4 K Teffp [4024/4130] Photometric effective temperature
34-37 F4.2 [cm/s2] loggp [0.3/0.8] Photometric log of surface gravity
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Note (1): The effective temperature, surface gravity, and microturbulent
velocity (ξt), were obtained by enforcing excitation and
ionization balance for Fe lines. The uncertainties in Teff, logg, and
ξt are 50K, 0.2dex, and 0.2km/s, respectively.
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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 A5 --- Ion Species identifier
7- 13 F7.2 0.1nm lambda [4057.8/7947.6]? Wavelength in Angstroms (1)
15- 18 F4.2 eV LEP [0/5.2]? Lower excitation potential
20- 25 F6.2 [-] log(gf) [-10.3/0.7]? Log oscillator strength
27- 31 F5.1 10-13m EW276 [20/150]? Equivalent width for ROA 276 (2)
33 A1 --- f_EW276 [s] s = spectrum synthesis
35- 39 F5.1 10-13m EW46 [19.8/150]? Equivalent width for ROA 46 (2)
41 A1 --- f_EW46 [s] s = spectrum synthesis
43- 47 F5.2 [-] loge276 [-1/8.1]? Log abundance for ROA 276
49- 53 F5.2 [-] loge46 [-1.3/7.6]? Log abundance for ROA 46
55- 56 I2 --- Ref [1/21] Source code (3)
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Note (1): The wavelength range for CH is 4270-4330Å.
Note (2): In units of milli-Angstroms
Note (3): Code as follows:
1 = Masseron et al. (2014, J/A+A/571/A47);
2 = Gratton et al. (2003, J/A+A/404/187) and references therein;
3 = values as used in Yong et al. (2005A&A...438..875Y 2005A&A...438..875Y) where the
references include Kurucz & Bell (1995, Atomic line list
(Cambridge: Smithsonian Astrophysical Observatory)),
Prochaska et al. (2000AJ....120.2513P 2000AJ....120.2513P),
Den Hartog et al. (2003ApJS..148..543D 2003ApJS..148..543D),
Ivans et al. (2001AJ....122.1438I 2001AJ....122.1438I), and
Ramirez & Cohen (2002AJ....123.3277R 2002AJ....123.3277R);
4 = Oxford group including Blackwell et al. (1979MNRAS.186..633B 1979MNRAS.186..633B),
Blackwell et al. (1979MNRAS.186..657B 1979MNRAS.186..657B),
Blackwell et al. (1980MNRAS.191..445B 1980MNRAS.191..445B),
Blackwell et al. (1986MNRAS.220..549B 1986MNRAS.220..549B),
Blackwell et al. (1995A&A...296..217B 1995A&A...296..217B);
5 = Kock & Richter (1968ZA.....69..180K 1968ZA.....69..180K);
6 = Hannaford & Lowe (1983OptEn..22..532H 1983OptEn..22..532H);
7 = Roederer & Lawler (2012, J/ApJ/750/76);
8 = mean of lifetimes from Simsarian et al. (1998PhRvA..57.2448S 1998PhRvA..57.2448S) and
Volz & Schmoranzer (1996PhST...65...48V 1996PhST...65...48V) weighted according to
uncertainties, via Morton (2000ApJS..130..403M 2000ApJS..130..403M);
9 = Wiese F. (2009, CRC Handbook of Chemistry and Physics
90th ed. (Boca Raton, FL: CRC Press) 10)
10 = Biemont et al. (2011MNRAS.414.3350B 2011MNRAS.414.3350B);
11 = Biemont et al. (1981ApJ...248..867B 1981ApJ...248..867B);
12 = Ljung et al. (2006A&A...456.1181L 2006A&A...456.1181L);
13 = Whaling & Brault (1988PhyS...38..707W 1988PhyS...38..707W);
14 = Davidson et al. (1992A&A...255..457D 1992A&A...255..457D) using hfs/IS
from McWilliam (1998AJ....115.1640M 1998AJ....115.1640M);
15 = Lawler et al. (2001ApJ...556..452L 2001ApJ...556..452L), using hfs
from Ivans et al. (2006, J/ApJ/645/613);
16 = Lawler et al. (2009, J/ApJS/182/51);
17 = Li et al. (2007PhyS...76..577L 2007PhyS...76..577L);
18 = Den Hartog et al. (2003ApJS..148..543D 2003ApJS..148..543D), using hfs/IS from
Roederer et al. (2008ApJ...675..723R 2008ApJ...675..723R) when available;
19 = Lawler et al. (2006, J/ApJS/162/227), using hfs/IS from
Roederer et al. (2008ApJ...675..723R 2008ApJ...675..723R) when available;
20 = Lawler et al. (2001ApJ...563.1075L 2001ApJ...563.1075L), using hfs/IS
from Ivans et al. (2006, J/ApJ/645/613);
21 = Biemont et al. (2000MNRAS.312..116B 2000MNRAS.312..116B), using hfs/IS
from Roederer et al. (2012ApJS..203...27R 2012ApJS..203...27R).
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 25-Oct-2017