J/A+A/665/A135 Chemical Evolution of Yb in Galactic Disc (Montelius+, 2022)
Chemical evolution of ytterbium in the Galactic disc.
Montelius M., Forsberg R., Ryde N., Joensson H., Afsar M., Johansen A.,
Kaplan K.F., Kim H., Mace G., Sneden C., Thorsbro B.
<Astron. Astrophys. 665, A135 (2022)>
=2022A&A...665A.135M 2022A&A...665A.135M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, K-type ; Stars, giant ; Abundances ; Spectra, infrared ;
Milky Way
Keywords: stars: abundances - stars: late-type - Galaxy: abundances -
Galaxy: disk - Galaxy: evolution - infrared: stars
Abstract:
Measuring the abundances of neutron-capture elements in Galactic disk
stars is an important part of understanding key stellar and galactic
processes. In the optical wavelength regime a number of different
neutron-capture elements have been measured; however, only the
s-process-dominated element cerium has been accurately measured for a
large sample of disk stars from the infrared H band. The more
r-process dominated element ytterbium has only been measured in a
small subset of stars so far.
In this study we aim to measure the ytterbium (Yb) abundance of local
disk giants using the Yb II line at λair=16498Å. We also
compare the resulting abundance trend with cerium and europium
abundances for the same stars to analyse the s- and r-process
contributions.
We analyse 30K giants with high-resolution H band spectra using
spectral synthesis. The very same stars have already been analysed
using high-resolution optical spectra via the same method, but it was
not possible to determine the abundance of Yb from those spectra due
to blending issues for stars with [Fe/H]>-1. In the present analysis,
we utilise the stellar parameters determined from the optical
analysis.
We determined the Yb abundances with an estimated uncertainty for
[Yb/Fe] of 0.1dex. By comparison, we found that the [Yb/Fe] trend
closely follows the [Eu/Fe] trend and has clear s-process enrichment
in identified s-rich stars. This comparison confirms both that the
validity of the Yb abundances is ensured and that the theoretical
prediction that the s-/r-process contribution to the origin of Yb of
roughly 40/60 is supported.
These results show that, with a careful and detailed analysis of
infrared spectra, reliable Yb abundances can be derived for a wider
sample of cooler giants in the range -1.1<[Fe/H]<0.3. This is
promising for further studies of the production of Yb and for the
r-process channel, key for galactochemical evolution, in the infrared.
Description:
We present Yb and Ce abundances measured from the infrared H band for
30 K giants in the solar neighbourhood. The spectra were obtained with
the spectrograph IGRINS at HJST and DCT. The spectra have R=45000. The
S/N of the spectra is generally high, with just one below 100 and
about half of them having values above 200.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 60 31 Observational data for sample
table3.dat 73 31 Stellar parameters and abundances for sample
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See also:
J/A+A/631/A113 : Abund. of disk+bulge giants: Zr, La, Ce, Eu (Forsberg+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Star Name (HD, HIP, KIC, 2M)
12 A1 --- n_Star [a] Note on Star (G1)
13- 29 A17 --- 2MASS 2MASS name (JHHMMSSss+DDMMSSs)
31- 34 F4.1 mag Hmag 2MASS H magnitude
36- 39 F4.1 mag Kmag 2MASS K magnitude
41- 50 A10 "date" Date Observation date
52- 55 A4 --- Tel Used telescope (1)
57- 60 I4 s ExpTime Exposure time
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Note (1): Used telescopes as follows:
DCT = Discovery Channel Telescope, a 4.3m telescope at Lowell Observatory,
Arizona
HJST = Harlan J Smith Telescope, a 2.7m telescope at McDonald Observatory,
Texas
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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- 11 A11 --- Star Name (HD, HIP, KIC, 2M)
12 A1 --- n_Star [a] Note on Star (G1)
13- 16 I4 K Teff Effective temperature
18- 20 F3.1 [cm/s2] logg Surface gravity
22- 26 F5.2 [-] [Fe/H] Relative iron abundance
28- 30 F3.1 km/s vmic Microturbulence velocity
32- 35 I4 pc Dist ? Distance (1)
37- 48 A12 --- Pop Designated stellar population (2)
50- 52 I3 --- S/N Signal-to-noise ratio (3)
54- 59 F6.3 [-] [Yb/Fe] Relative Ytterbium abundance
61- 66 F6.3 [-] [Eu/Fe] ? Relative Europium abundance (4)
68- 73 F6.3 [-] [Ce/Fe] Relative Cerium abundance
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Note (1): As measured by Paul J. McMillan, 2018RNAAS...2...51M 2018RNAAS...2...51M.
No measurements for very nearby stars.
Note (2): Based on kinematics and [Mg/Fe], see Sect. 3.2. S-rich designation
from s-element abundances in Joensson et al. (in prep.)
Note (3): Determined using DER_SNR, Stoerh et al., 2008ASPC..394..505S 2008ASPC..394..505S.
Note (4): As measured by Forsberg et al. (2019A&A...631A.113F 2019A&A...631A.113F).
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Global notes:
Note (G1): a: Data from the IGRINS Spectral Library
(Park et al., 2018ApJS..238...29P 2018ApJS..238...29P, Cat. J/ApJS/238/29)
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Acknowledgements:
Martin Montelius, montelius(at)astro.rug.nl
References:
Jonsson et al. (in prep.)
McMillan, 2018RNAAS...2...51M 2018RNAAS...2...51M
Stoerh et al., 2008ASPC..394..505S 2008ASPC..394..505S
Forsberg et al. 2019A&A...631A.113F 2019A&A...631A.113F, Cat. J/A+A/631/A113
Park et al., 2018ApJS..238...29P 2018ApJS..238...29P, Cat. J/ApJS/238/29
(End) Patricia Vannier [CDS] 11-May-2022