J/A+A/631/A113 Abund. of disk & bulge giants: Zr, La, Ce, Eu (Forsberg+, 2019)
Abundances of disk and bulge giants from high-resolution optical spectra.
IV. Zr, La, Ce, Eu.
Forsberg R., Joensson H., Ryde N., Matteucci F.
<Astron. Astrophys. 631, A113 (2019)>
=2019A&A...631A.113F 2019A&A...631A.113F (SIMBAD/NED BibCode)
ADC_Keywords: Stars, giant ; Abundances ; Spectroscopy
Keywords: stars: abundances - Galaxy: bulge - solar neighborhood -
Galaxy: evolution
Abstract:
Observations of the Galactic bulge suggest that the disk formed
through secular evolution rather than gas dissipation and/or mergers,
as previously believed. This would imply very similar chemistry in the
disk and bulge. Some elements, such as the α-elements, are well
studied in the bulge, but others like the neutron-capture elements are
much less well explored. Stellar mass and metallicity are factors that
affect the neutron-capture process. Due to this, the enrichment of the
ISM and the abundance of neutron-capture elements vary with time,
making them suitable probes for Galactic chemical evolution.
In this work, we make a differential comparison of neutron-capture
element abundances determined in the local disk(s) and the bulge,
focusing on minimising possible systematic effects in the analysis,
with the aim of finding possible differences/similarities between the
populations.
Abundances are determined for Zr, La, Ce, and Eu in 45 bulge giants
and 291 local disk giants, from high-resolution optical spectra. The
abundances are determined by fitting synthetic spectra using the
SME-code. The disk sample is separated into thin- and thick-disk
components using a combination of abundances and kinematics.
We find flat Zr, La, and Ce trends in the bulge, with a ∼0.1dex higher
La abundance compared with the disk, possibly indicating a higher
s-process contribution for La in the bulge. [Eu/Fe] decreases with
increasing [Fe/H], with a plateau at around [Fe/H]~-0.4, pointing at
similar enrichment to α-elements in all populations.
We find that the r-process dominated the neutron-capture production at
early times both in the disks and bulge. Further, [La/Eu] ratios for
the bulge are systematically higher than for the thick disk, pointing
to either a) a different amount of SN II or b) a different
contribution of the s-process in the two populations. Considering
[(La+Ce)/Zr], the bulge and the thick disk follow each other closely,
suggesting a similar ratio of high-to-low-mass asymptotic giant branch
stars.
Description:
We present abundances of four neutron-capture elements: Zr, La, Ce,
and Eu for 291 K giants in the solar neighborhood and 45 K giants in
the bulge. For the local disk stars, we used observations obtained
with the spectrograph FIES at NOT, and from archives (FIES and
PolarBase), while for the bulge stars, the observations were taken
with the UVES/FLAMES spectrograph at VLT. The FIES spectra have
R=67000, the PolarBase spectra have R=67000, and the UVES/FLAMES
spectra have R=47000. In general, most disk stars are very bright and
have S/N around 100, the bulge stars are fainter with S/R of 10-80.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 51 45 Basic data for the observed bulge giants
tablea2.dat 109 291 Basic data for the observed disk giants
tablea3.dat 85 45 Stellar parameters and abundances for observed
bulge giants
tablea4.dat 91 291 Stellar parameters and abundances for observed
disk giants
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See also:
J/A+A/543/A160 : Normalized spectra of 82 Kepler red giants (Thygesen+, 2012)
J/A+A/598/A100 : Abundances of disk giants: O, Mg, Ca and Ti (Jonsson+, 2017)
J/A+A/625/A141 : Abundances of disk and bulge giants: Sc, V, Cr, Mn, Co, Ni
(Lomaeva+, 2019)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Name Name
10- 11 I2 h RAh Right ascension (J2000)
13- 14 I2 min RAm Right ascension (J2000)
16- 21 F6.3 s RAs Right ascension (J2000)
25 A1 --- DE- Declination sign (J2000)
26- 27 I2 deg DEd Declination (J2000)
29- 30 I2 arcmin DEm Declination (J2000)
32- 36 F5.2 arcsec DEs Declination (J2000)
40- 45 F6.3 mag Vmag V magnitude
50- 51 I2 --- S/N Signal-to-noise ratio (1)
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Note (1): As measured by http://www.stecf.org/software/ASTROsoft/DER_SNR
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Name Name (HIP, KIC or TYC)
17- 32 A16 --- AName Alternative name
37- 38 I2 h RAh Right ascension (J2000)
40- 41 I2 min RAm Right ascension (J2000)
43- 50 F8.5 s RAs Right ascension (J2000)
54 A1 --- DE- Declination sign (J2000)
55- 56 I2 deg DEd Declination (J2000)
58- 59 I2 arcmin DEm Declination (J2000)
61- 67 F7.4 arcsec DEs Declination (J2000)
70- 74 F5.2 mag Vmag V magnitude
78- 84 F7.2 km/s RV Radial velocity
89- 91 I3 --- S/N Signal-to-noise ratio (1)
95-109 A15 --- Source Source of spectrum (2)
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Note (1): As measured by http://www.stecf.org/software/ASTROsoft/DER_SNR
Note (2): Thygesen+2012 for Thygesen et al., 2012, Cat. J/A+A/543/160.
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Byte-by-byte Description of file: tablea3.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Name Name
12- 15 I4 K Teff Effective temperature
22- 25 F4.2 [cm/s2] logg Surface gravity
31- 35 F5.2 [-] [Fe/H] Relative iron abundance
42- 45 F4.2 km/s Vmic Microturbulence velocity
48- 55 F8.2 --- A(Zr) ?=-9999 Zirconium abundance
58- 65 F8.2 --- A(La) ?=-9999 Lanthanum abundance
68- 75 F8.2 --- A(Ce) ?=-9999 Cerium abundance
78- 85 F8.2 --- A(Eu) ?=-9999 Europium abundance
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Byte-by-byte Description of file: tablea4.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Name Name (HIP, KIC or TYC)
18- 21 I4 K Teff Effective temperature
28- 31 F4.2 [cm/s2] logg Surface gravity
37- 41 F5.2 [-] [Fe/H] Relative iron abundance
48- 51 F4.2 km/s Vmic Microturbulence velocity
54- 61 F8.2 --- A(Zr) ?=-9999 Zirconium abundance
68- 71 F4.2 --- A(La) Lanthanum abundance
74- 81 F8.2 --- A(Ce) ?=-9999 Cerium abundance
87- 91 F5.2 --- A(Eu) Europium abundance
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Acknowledgements:
Rebecca Forsberg, rebecca(at)astro.lu.se
References:
Jonsson et al., Paper I 2017A&A...598A.100J 2017A&A...598A.100J, Cat. J/A+A/598/A100
Jonsson et al., Paper II 2017A&A...598A.101J 2017A&A...598A.101J
Lomaeva et al., Paper III. 2019A&A...625A.141L 2019A&A...625A.141L
(End) Patricia Vannier [CDS] 03-Oct-2019