J/AJ/145/107 Zr, Ba, La, and Eu abundances in 19 open clusters (Jacobson+, 2013)
Zirconium, barium, lanthanum, and europium abundances in open clusters.
Jacobson H.R., Friel E.D.
<Astron. J., 145, 107 (2013)>
=2013AJ....145..107J 2013AJ....145..107J
ADC_Keywords: Clusters, open ; Stars, giant ; Abundances
Keywords: Galaxy: abundances - stars: abundances
Abstract:
We present an analysis of the s-process elements Zr, Ba, and La and
the r-process element Eu in a sample of 50 stars in 19 open clusters.
Stellar abundances of each element are based on measures of a minimum
of two lines per species via both equivalent width and spectrum
synthesis techniques. We investigate cluster mean neutron-capture
abundance trends as a function of cluster age and location in the
Milky Way disk and compare them to results found in other studies in
the literature. We find a statistically significant trend of
increasing cluster [Ba/Fe] as a function of decreasing cluster age, in
agreement with recent findings for other open cluster samples,
supporting the increased importance of low-mass asymptotic giant
branch stars to the generation of s-process elements. However, the
other s-process elements, [La/Fe] and [Zr/Fe], do not show similar
dependences, in contrast to theoretical expectations and the limited
observational data from other studies. Conversely, cluster [Eu/Fe]
ratios show a slight increase with increasing cluster age, although
with marginal statistical significance. Ratios of [s/r]-process
abundances, [Ba/Eu] and [La/Eu], however, show more clearly the
increasing efficiency of s-process relative to r-process enrichment in
open cluster chemical evolution, with significant increases among
younger clusters. Last, cluster neutron-capture element abundances
appear to be independent of Galactocentric distance. We conclude that
a homogeneous analysis of a larger sample of open clusters is needed
to resolve the apparent discrepant conclusions between different
studies regarding s-process element abundance trends with age to
better inform models of galactic chemical evolution.
Description:
The cluster sample used in this work is shown in Table1. Much of our
stellar sample has been presented in previous work, and is comprised
of echelle spectra from KPNO 4m and Hobby-Eberly telescopes (see Friel
et al., 2005, cat. J/AJ/129/2725, and 2010, cat. J/AJ/139/1942;
Jacobson et al., 2008AJ....135.2341J 2008AJ....135.2341J, and 2009, cat. J/AJ/137/4753).
This sample includes stars in the clusters Be 17, Be 32, Be 39, M67,
NGC 188, NGC 1193, NGC 1817, NGC 1883, NGC 2141, NGC 2158, and NGC
7142. The reader is referred to references above for details regarding
the observations about the stellar targets.
Additional high-resolution spectra of stars in clusters Be 18, Be 21,
Be 22, Be 32, and PWM 4 obtained with the High Resolution Echelle
Spectrometer (HIRES) spectrograph on Keck were kindly given to us by
D. Yong. We refer the reader to Yong et al. (2012, cat. J/AJ/144/95)
for details regarding the observations of these spectra.
We obtained new observations of stars in open clusters NGC 1245, NGC
2194, NGC 2355, and NGC 6939 using the echelle spectrograph on the
KPNO 4m Mayall telescope in 2010 November.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 47 19 Cluster sample
table2.dat 55 50 Stellar atmospheric parameters and Fe abundances
table3.dat 51 10 Line list
table4.dat 42 50 Individual star [Zr/Fe] ratios
table5.dat 42 50 Individual star [Ba/Fe] ratios
table6.dat 46 50 Individual star [La/Fe] ratios
table7.dat 46 50 Individual star [Eu/Fe] ratios
table8.dat 66 19 Cluster mean abundances
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See also:
J/MNRAS/419/1350 : Red giants abundances in 4 open clusters (Reddy+, 2012)
J/AJ/144/95 : Stars abundance in the outer galactic disk. IV. (Yong+, 2012)
J/AJ/142/59 : Chemical abundance in 10 open clusters (Jacobson+, 2011)
J/A+A/535/A30 : Chemical abundance of stars in open clusters (Carrera+, 2011)
J/A+A/360/499 : Equivalent widths of 9 stars of M 67 (Tautvaisiene+, 2000)
J/A+A/511/A56 : Abundances of five open clusters (Pancino+, 2010)
J/AJ/139/1942 : EWs of red giants in 6 open clusters (Friel+, 2010)
J/AJ/137/4753 : Red giants EWs in 4 open clusters (Jacobson+, 2009)
J/AJ/134/1216 : Abundances of NGC 7142, 6939, IC 4756 stars (Jacobson+, 2007)
J/AJ/129/2725 : Equivalent widths of red giants in Berkeley 17 (Friel+, 2005)
J/A+A/360/499 : Equivalent widths of 9 stars of M 67 (Tautvaisiene+, 2000)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Cluster Cluster name
10- 14 F5.2 Gyr Age Cluster age (adopted from Salaris et al.,
2004A&A...414..163S 2004A&A...414..163S) (1)
15 A1 --- f_Age [d] Cluster age from Villanova et al. 2007 (1)
17- 19 F3.1 kpc Dist Distance
21- 24 F4.1 kpc Rgc Galactocentric distance (R☉=8.5kpc)
26- 30 A5 --- Ref Reference for distances (2)
32 I1 --- N1 Number of stars
34 I1 --- N2 ? Number of stars (from spectra obtained on Keck)
36- 47 A12 --- Tel Telescope (KPNO4m, Keck, or HET) (3)
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Note (1): NGC 1883 is not included in the sample of Salaris et al.
(2004A&A...414..163S 2004A&A...414..163S); the age is from Villanova et al.
et al. (2007MNRAS.379.1089V 2007MNRAS.379.1089V; uncertainty 0.07Gyr).
Note (2): Reference as follows:
A04 = Andreuzzi et al. (2004MNRAS.348..297A 2004MNRAS.348..297A);
F05 = Friel et al. (2005, cat. J/AJ/129/2725);
FJP10 = Friel et al. (2010, cat. J/AJ/139/1942);
J08 = Jacobson et al. (2008AJ....135.2341J 2008AJ....135.2341J);
J09 = Jacobson et al. (2009, cat. J/AJ/137/4753);
J11 = Jacobson et al. (2011, cat. J/AJ/142/59);
Y12 = Yong et al. (2012, cat. J/AJ/144/95).
Note (3): Telescope as follows:
KPNO4m = Observations from previous works (Friel et al., 2005,
cat. J/AJ/129/2725, and 2010, cat. J/AJ/139/1942; Jacobson et al.,
2008AJ....135.2341J 2008AJ....135.2341J, and 2009, cat. J/AJ/137/4753) for the clusters
Be17, Be32, Be39, M67, NGC188, NGC1817, NGC1883, NGC2141, NGC2158, and
NGC7142. We obtained new observations of stars in open clusters
NGC1245, NGC2194, NGC2355, and NGC6939 using the echelle spectrograph
on the KPNO 4m Mayall telescope in 2010 November;
Keck = Additional high-resolution spectra of stars in clusters Be18, Be21,
Be22, Be32, and PWM4 obtained with the High Resolution Echelle
Spectrometer (HIRES) spectrograph on Keck were kindly given to us by
D. Yong (2012, cat. J/AJ/144/95);
HET = Hobby-Eberly Telescope (see Friel et al., 2010, cat. J/AJ/139/1942).
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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- 8 A8 --- Cluster Cluster name
10- 13 A4 --- Star Star name (in Cluster)
15- 18 I4 K Teff Effective temperature
20- 22 F3.1 [cm/s2] logg Surface gravity
24- 27 F4.2 km/s vt Microturbulent velocity
29- 33 F5.2 [Sun] [FeI/H] Metallicity from FeI lines (1)
35- 38 F4.2 [Sun] s_[FeI/H] 1σ standard deviation in [FeI/H]
40- 41 I2 --- o_[FeI/H] Number of FeI lines
43- 47 F5.2 [Sun] [FeII/H] Metallicity from FeII lines (1)
49- 52 F4.2 [Sun] s_[FeII/H] 1σ standard deviation in [FeII/H]
54- 55 I2 --- o_[FeII/H] Number of FeII lines
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Note (1): The [Fe/H] values are relative to a solar logε(Fe)=7.52, the
default used in MOOG (see Sneden et al., 1991AJ....102.2001S 1991AJ....102.2001S).
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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 A5 --- El Element/Ion (Zr I, Ba II, La II, or Eu II)
7- 13 F7.2 0.1nm lambda Wavelength (Å)
15- 19 F5.3 eV EP Excitation potential
21- 26 F6.3 [-] loggf Log of the oscillator strength
28 A1 --- f_loggf [e] Origin of loggf (2)
30- 33 F4.2 [-] Abund1 Element Solar abundance (logε(Fe)) (3)
35- 38 F4.2 [-] Abund2 Element Solar abundance (logε(Fe)) (4)
40- 43 F4.2 [-] Abund3 Element Arcturus abundance (logε(X)) (5)
45 A1 --- f_Abund3 [f] This abundance is forced to match that for
the EuII 6645 feature; details in Section 3.2.4
47- 51 F5.2 [Sun] [X/Fe] Arcturus [X/Fe] ratio (6)
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Note (2):
e = The total log(gf) for the feature; log(gf)'s for the individual components
in La and Eu are presented in Lawler et al. (2001ApJ...556..452L 2001ApJ...556..452L) and
Lawler et al. (2001ApJ...563.1075L 2001ApJ...563.1075L), respectively. Total log(gf)'s and those
of individual components for Ba are adopted from McWilliam
(1998AJ....115.1640M 1998AJ....115.1640M) and Prochaska et al. (2000AJ....120.2513P 2000AJ....120.2513P).
Note (3): Literature values as described in the text (logε(Zr) and
logε(Ba) from Anders & Grevesse, 1989GeCoA..53..197A 1989GeCoA..53..197A;
logε(La) from Lawler et al., 2001ApJ...556..452L 2001ApJ...556..452L).
Note (4): Values found via equivalent width measures (Zr, Ba) or spectrum
synthesis (La, Eu) in this work, as described in Section 3.2.
Note (5): This study.
Note (6): Calculated relative to literature solar values, adopting
[Fe/H]=-0.50.
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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- 8 A8 --- Cluster Cluster name
10- 13 A4 --- Star Star name
15- 19 F5.2 [Sun] [Zr/Fe]1 Abundance from the ZrIλ6127 lines (7)
21- 25 F5.2 [Sun] [Zr/Fe]2 ? Abundance from ZrIλ6134 lines (7)
27- 31 F5.2 [Sun] [Zr/Fe]3 Abundance from the ZrIλ6143 lines (7)
33- 37 F5.2 [Sun] <[Zr/Fe]> Mean star [Zr/Fe] abundance
39- 42 F4.2 [Sun] s_<[Zr/Fe]> 1σ standard deviation in <[Zr/Fe]>
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Note (7): Based on equivalent widths measurements and calculated relative to the
[FeI/H] ratios given in Table2.
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Cluster Cluster name
10- 13 A4 --- Star Star name
15- 19 F5.2 [Sun] [Ba/Fe]1 Abundance from the BaIIλ5853 lines (8)
21- 25 F5.2 [Sun] [Ba/Fe]2 Abundance from the BaIIλ6141 lines (8)
27- 31 F5.2 [Sun] [Ba/Fe]3 Abundance from the BaIIλ6496 lines (8)
33- 37 F5.2 [Sun] <[Ba/Fe]> Mean star [Ba/Fe] abundance (9)
39- 42 F4.2 [Sun] s_<[Ba/Fe]> 1σ standard deviation in <[Ba/Fe]> (9)
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Note (8): Calculated using measured equivalent width. Note that these [Ba/Fe]
ratios are calculated relative to our determined solar Ba abundances in
Column 6 of Table3, to minimize systematics due to the zero point of our
abundance scale.
Note (9): Calculated from the λ5853 and λ6496 lines only.
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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- 8 A8 --- Cluster Cluster name
10- 13 A4 --- Star Star name
15- 19 F5.2 [Sun] [La/Fe]1 ? Abundance from LaIIλ6262 lines (10)
21- 24 F4.2 [Sun] e_[La/Fe]1 ? Uncertainty in [La/Fe]1 (11)
26- 30 F5.2 [Sun] [La/Fe]2 ? Abundance from LaIIλ6390 lines (10)
32- 35 F4.2 [Sun] e_[La/Fe]2 ? Uncertainty in [La/Fe]2 (11)
37- 41 F5.2 [Sun] <[La/Fe]> ? Mean star [La/Fe] abundance
43- 46 F4.2 [Sun] s_<[La/Fe]> ? 1σ standard deviation in <[La/Fe]>
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Note (10): Determined via spectrum synthesis.
Note (11): Represents the measurement uncertainty in the synthesis technique.
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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 --- Cluster Cluster name
10- 13 A4 --- Star Star name
15- 19 F5.2 [Sun] [Eu/Fe]1 ? Abundance from EuIIλ6437 lines (12)
21- 24 F4.2 [Sun] e_[Eu/Fe]1 ? Uncertainty in [Eu/Fe]1 (13)
26- 30 F5.2 [Sun] [Eu/Fe]2 ? Abundance from EuIIλ6645 lines (12)
32- 35 F4.2 [Sun] e_[Eu/Fe]2 ? Uncertainty in [Eu/Fe]2 (13)
37- 41 F5.2 [Sun] <[Eu/Fe]> ? Mean star [Eu/Fe] abundance
43- 46 F4.2 [Sun] s_<[Eu/Fe]> ? 1σ standard deviation in <[Eu/Fe]>
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Note (12): Determined via spectrum synthesis.
Note (13): Represents the measurement uncertainty in the synthesis technique.
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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- 8 A8 --- Cluster Cluster name
9 A1 --- C [ab] Calculation of [X/Fe] ratios (4)
11- 15 F5.2 [Sun] [Fe/H] Cluster mean [Fe/H] abundance
17- 20 F4.2 [Sun] s_[Fe/H] 1σ standard deviation in [Fe/H]
22- 26 F5.2 [Sun] [Zr/H] Cluster mean [Zr/H] abundance
28- 31 F4.2 [Sun] s_[Zr/H] 1σ standard deviation in [Zr/H]
33- 37 F5.2 [Sun] [Ba/Fe] Cluster mean [Ba/Fe] abundance
39- 42 F4.2 [Sun] s_[Ba/Fe] 1σ standard deviation in [Ba/Fe]
44- 48 F5.2 [Sun] [La/Fe] Cluster mean [La/Fe] abundance
50- 53 F4.2 [Sun] s_[La/Fe] 1σ standard deviation in [La/Fe]
55- 59 F5.2 [Sun] [Eu/Fe] ? Cluster mean [Eu/Fe] abundance
61- 64 F4.2 [Sun] s_[Eu/Fe] ? 1σ standard deviation in [Eu/Fe]
66 I1 --- N Number of stars used to determined the mean
abundances (5)
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Note (4): Flag as follows:
a = [X/Fe] ratios calculated without star 643;
b = [X/Fe] ratios calculated without star 190.
Note (5): Given that 643 is high up on the red giant branch relative to 414, we
have taken the abundances of star 414 to be more reliable, and therefore we
have adopted the abundances of star 414 as representative of those for
Be22 as a whole. The abundances reported for Be22 are exactly those of star
414. Stars in cluster NGC6939 show a pattern in which one star, 190, is
consistently enhanced in [X/Fe] ratios. Star 190 resides in the clump and
shows [s/Fe] ratios at least 0.4dex larger than the other stars. As a
result we do not include it in cluster mean abundance calculations.
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(End) Sylvain Guehenneux [CDS] 06-May-2014