J/A+A/586/A125 Neutron-capture elements abundances in Cepheids (da Silva+ 2016)
On the neutron-capture elements across the Galactic thin disk using Cepheids.
da Silva R., Lemasle B., Bono G., Genovali K., McWilliam A., Cristallo S.,
Bergemann M., Buonanno R., Fabrizio M., Ferraro I., Francois P.,
Iannicola G., Inno L., Laney C.D., Kudritzki R.-P., Matsunaga N., Nonino M.,
Primas F., Przybilla N., Romaniello M., Thevenin F., Urbaneja M.A.
<Astron. Astrophys. 586, A125 (2016)>
=2016A&A...586A.125D 2016A&A...586A.125D (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Stars, variable ; Abundances ; Spectroscopy
Keywords: stars: abundances - stars: variables: Cepheids -
stars: oscillations - open clusters and associations: general -
Galaxy: disk
Abstract:
We present new accurate abundances for five neutron-capture (Y, La,
Ce, Nd, Eu) elements in 73 classical Cepheids located across the
Galactic thin disk. Individual abundances are based on high spectral
resolution (R∼38000) and high signal-to-noise ratio (S/N∼50-300)
spectra collected with UVES at ESO VLT for the DIONYSOS project.
Taking account for similar Cepheid abundances provided either by our
group (111 stars) or available in the literature, we end up with a
sample of 435 Cepheids covering a broad range in iron abundances
(-1.6<[Fe/H]<0.6). We found, using homogeneous individual distances
and abundance scales, well defined gradients for the above elements.
However, the slope of the light s-process element (Y) is at least a
factor of two steeper than the slopes of heavy s- (La, Ce, Nd) and
r- (Eu) process elements. The s to r abundance ratio ([La/Eu]) of
Cepheids shows a well defined anticorrelation with of both Eu and Fe.
On the other hand, Galactic field stars attain an almost constant
value and only when they approach solar iron abundance display a mild
enhancement in La. The [Y/Eu] ratio shows a mild evidence of a
correlation with Eu and, in particular, with iron abundance for field
Galactic stars. We also investigated the s-process index -- [hs/ls] --
and we found a well defined anticorrelation, as expected, between
[La/Y] and iron abundance. Moreover, we found a strong correlation
between [La/Y] and [La/Fe] and, in particular, a clear separation
between Galactic and Sagittarius red giants. Finally, the comparison
between predictions for low-mass asymptotic giant branch stars and the
observed [La/Y] ratio indicate a very good agreement over the entire
metallicity range covered by Cepheids. However, the observed spread,
at fixed iron content, is larger than predicted by current models.
Description:
The abundances of Fe, Y, La, Ce, Nd, and Eu for our sample of 73
Cepheids plus data available in the literature for other 362 Cepheids
are shown. We first show the abundances derived based on individual
spectra for the 73 stars, then the averaged values, and finally the
data from the literature. The original abundances available in the
literature were rescaled according to the zero-point differences
listed in Table 5. The priority was given in the following order: we
first adopt the abundances provided by our group, this study (TS) and
Lemasle et al. (2013A&A...558A..31L 2013A&A...558A..31L, LEM), and then those provided by
the other studies, Luck & Lambert (2011AJ....142..136L 2011AJ....142..136L, LIII), and
Luck et al. (2011AJ....142...51L 2011AJ....142...51L, LII).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 123 120 Fe, Y, La, Ce, Nd, and Eu abundances for the 73
Cepheids based on individual spectra
table3.dat 110 73 Mean abundances of Fe, Y, La, Ce, Nd, and Eu for
the 73 Cepheids
table4.dat 23 165 Hyperfine structure list for some of the lines
in our linelist
table7.dat 109 435 Y, La, Ce, Nd, and Eu abundances for the whole
sample of 435 Galactic Cepheids
(the current 73 plus 362 from the literature)
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See also:
J/AJ/142/51 : Galactic Cepheids abundance variations (Luck+, 2011)
J/AJ/142/136 : Spectroscopy of Cepheids. l=30-250° (Luck+, 2011)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Cepheid name
12- 20 F9.3 --- MJD Modified Julian Day
23- 27 F5.2 --- [Fe/H] Metallicity [Fe/H] based on FeI and FeII
30- 33 F4.2 --- e_[Fe/H] Standard deviation on [Fe/H]
36- 38 I3 --- NFeI Number of FeI lines used
41- 42 I2 --- NFeII Number of FeII lines used
45- 49 F5.2 --- [Y/H] Yttrium abundance [Y/H]
52- 55 F4.2 --- e_[Y/H] Dispersion around the mean on [Y/H]
58 I1 --- NY Number of YII lines used
61- 65 F5.2 --- [La/H] ? Lanthanum abundance [La/H]
68- 71 F4.2 --- e_[La/H] ? Dispersion around the mean on [La/H]
74 I1 --- NLa ? Number of LaII lines used
77- 81 F5.2 --- [Ce/H] ? Cerium abundance [Ce/H]
84- 87 F4.2 --- e_[Ce/H] ? Dispersion around the mean [Ce/H]
90 I1 --- NCe ? Number of CeII lines used
93- 97 F5.2 --- [Nd/H] ? Neodymium abundance [Nd/H]
100-103 F4.2 --- e_[Nd/H] ? Dispersion around the mean [Nd/H]
106-107 I2 --- NNd ? Number of NdII lines used
110-114 F5.2 --- [Eu/H] ? Europium abundance [Eu/H]
117-120 F4.2 --- e_[Eu/H] ? Dispersion around the mean [Eu/H]
123 I1 --- NEu ? Number of EuII lines used
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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- 9 A9 --- Name Cepheid name
12- 17 F6.4 [d] logP logarithmic pulsation period
20- 24 I5 kpc RG Galactocentric distance
27- 29 I3 kpc e_RG Error in the Galactocentric distance
32- 36 F5.2 --- [Fe/H] Metallicity [Fe/H] based on FeI and FeII
39- 42 F4.2 --- e_[Fe/H] Standard deviation on [Fe/H]
45- 49 F5.2 --- [Y/H] Yttrium abundance [Y/H]
52- 55 F4.2 --- e_[Y/H] Dispersion around the mean on [Y/H]
58- 62 F5.2 --- [La/H] ? Lanthanum abundance [La/H]
65- 68 F4.2 --- e_[La/H] ? Dispersion around the mean on [La/H]
71- 75 F5.2 --- [Ce/H] ? cerium abundance [Ce/H]
78- 81 F4.2 --- e_[Ce/H] ? Dispersion around the mean on [Ce/H]
84- 88 F5.2 --- [Nd/H] ? Neodymium abundance [Nd/H]
91- 94 F4.2 --- e_[Nd/H] ? Dispersion around the mean on [Nd/H]
97-101 F5.2 --- [Eu/H] ? europium abundance [Eu/H]
104-107 F4.2 --- e_[Eu/H] ? Dispersion around the mean on [Eu/H]
110 I1 --- Nsp ? Number of spectra available for each star
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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 A5 --- Ion Atomic line identification
8- 15 F8.3 0.1nm lambda Spectral line central wavelength
18- 23 F6.3 [-] loggf Logarithmic statistical weight of the lower
level multiplied by the oscillator strength
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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- 9 A9 --- Name Cepheid name
12- 16 F5.2 --- [Y/H]L ? [Y/H] abundance from literature (original)
19- 23 F5.2 --- [Y/H] ? [Y/H] abundance from literature (rescaled)
26- 29 A4 --- r_[Y/H]L ? Reference for the literature abundances (1)
32- 36 F5.2 --- [La/H]L ? [La/H] abundance from literature (original)
39- 43 F5.2 --- [La/H] ? [La/H] abundance from literature (rescaled)
46- 49 A4 --- r_[La/H]L ? Reference for the literature abundances (1)
52- 56 F5.2 --- [Ce/H]L ? [Ce/H] abundance from literature (original)
59- 63 F5.2 --- [Ce/H] ? [Ce/H] abundance from literature (rescaled)
66- 69 A4 --- r_[Ce/H]L ? Reference for the literature abundances (1)
72- 76 F5.2 --- [Nd/H]L ? [Nd/H] abundance from literature (original)
79- 83 F5.2 --- [Nd/H] ? [Nd/H] abundance from literature (rescaled)
86- 89 A4 --- r_[Nd/H]L ? Reference for the literature abundances (1)
92- 96 F5.2 --- [Eu/H]L ? [Eu/H] abundance from literature (original)
99-103 F5.2 --- [Eu/H] ? [Eu/H] abundance from literature (rescaled)
106-109 A4 --- r_[Eu/H]L ? Reference for the literature abundances (1)
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Note (1): The references are identified as follows:
TS = this study
LII = Luck et al., 2011AJ....142...51L 2011AJ....142...51L, Cat. J/AJ/142/51
LIII = Luck & Lambert, 2011AJ....142..136L 2011AJ....142..136L, Cat. J/AJ/142/136
LEM = Lemasle et al., 2013A&A...558A..31L 2013A&A...558A..31L
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Acknowledgements:
Ronaldo Da Silva, ron.oliveirasilva(at)gmail.com
(End) Patricia Vannier [CDS] 05-Nov-2015