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Chemical evolution of ytterbium in the Galactic disk*

Montelius, M. ; Forsberg, R. LU ; Ryde, N. LU orcid ; Jönsson, H. ; Afşar, M. ; Johansen, A. LU ; Kaplan, K. F. ; Kim, H. LU ; Mace, G. and Sneden, C. , et al. (2022) In Astronomy and Astrophysics 665.
Abstract

Context. 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. Aims. In this study we aim to measure the ytterbium (Yb) abundance of local disk giants using the Yb II line at λair = 16 498. We also compare the resulting abundance trend with cerium and europium abundances for the same stars to analyse... (More)

Context. 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. Aims. In this study we aim to measure the ytterbium (Yb) abundance of local disk giants using the Yb II line at λair = 16 498. We also compare the resulting abundance trend with cerium and europium abundances for the same stars to analyse the s- and r-process contributions. Methods. We analyse 30 K 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. Results. We determined the Yb abundances with an estimated uncertainty for [Yb/Fe] of 0.1 dex. 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. Conclusions. 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 range1.1 < [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.

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organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Galaxy: abundances, Galaxy: disk, Galaxy: evolution, Infrared: stars, Stars: abundances, Stars: late-type
in
Astronomy and Astrophysics
volume
665
article number
A135
publisher
EDP Sciences
external identifiers
  • scopus:85139844487
ISSN
0004-6361
DOI
10.1051/0004-6361/202243140
language
English
LU publication?
yes
id
4d67aa97-44e8-40f3-a219-780ab3a576de
date added to LUP
2022-12-16 14:52:31
date last changed
2024-04-17 23:38:16
@article{4d67aa97-44e8-40f3-a219-780ab3a576de,
  abstract     = {{<p>Context. 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. Aims. In this study we aim to measure the ytterbium (Yb) abundance of local disk giants using the Yb II line at λair = 16 498. We also compare the resulting abundance trend with cerium and europium abundances for the same stars to analyse the s- and r-process contributions. Methods. We analyse 30 K 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] &gt; 1. In the present analysis, we utilise the stellar parameters determined from the optical analysis. Results. We determined the Yb abundances with an estimated uncertainty for [Yb/Fe] of 0.1 dex. 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. Conclusions. 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 range1.1 &lt; [Fe/H] &lt; 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.</p>}},
  author       = {{Montelius, M. and Forsberg, R. and Ryde, N. and Jönsson, H. and Afşar, M. and Johansen, A. and Kaplan, K. F. and Kim, H. and Mace, G. and Sneden, C. and Thorsbro, B.}},
  issn         = {{0004-6361}},
  keywords     = {{Galaxy: abundances; Galaxy: disk; Galaxy: evolution; Infrared: stars; Stars: abundances; Stars: late-type}},
  language     = {{eng}},
  publisher    = {{EDP Sciences}},
  series       = {{Astronomy and Astrophysics}},
  title        = {{Chemical evolution of ytterbium in the Galactic disk*}},
  url          = {{http://dx.doi.org/10.1051/0004-6361/202243140}},
  doi          = {{10.1051/0004-6361/202243140}},
  volume       = {{665}},
  year         = {{2022}},
}