Chemical evolution of ytterbium in the Galactic disk

Autor: M. Montelius, R. Forsberg, N. Ryde, H. Jönsson, M. Afşar, A. Johansen, K. F. Kaplan, H. Kim, G. Mace, C. Sneden, B. Thorsbro
Přispěvatelé: Astronomy
Jazyk: angličtina
Rok vydání: 2022
Předmět:
Zdroj: Astronomy and astrophysics, 665:A135. EDP Sciences
ISSN: 0004-6361
Popis: 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 lambda(air) = 16 498 angstrom. 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 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.
Dutch Research Council (NWO) [VI.Vidi.193.093]; Goran Gustafsson Foundation for Research in Natural Sciences and Medicine; Royal Physiographic Society in Lund through the Stiftelse Walter Gyllenbergs fond; Mt. Cuba Astronomical Foundation; US National Science Foundation [AST-1229522, AST-1702267]; Korean GMT Project of KASI; Gemini Observatory; McDonald Observatory of the University of Texas at Austin
M.M. acknowledges funding through VIDI grant Pushing Galactic Archaeology to its limits VI.Vidi.193.093, which is funded by the Dutch Research Council (NWO). R.F's and A.J's research is supported by the Goran Gustafsson Foundation for Research in Natural Sciences and Medicine. R.F. and N.R. acknowledge support from the Royal Physiographic Society in Lund through the Stiftelse Walter Gyllenbergs fond and Marta och Erik Holmbergs donation. This work used the Immersion Grating Infrared Spectrometer (IGRINS) that was developed under a collaboration between the University of Texas at Austin and the Korea Astronomy and Space Science Institute (KASI) with the financial support of the Mt. Cuba Astronomical Foundation, of the US National Science Foundation under grants AST-1229522 and AST-1702267, of the McDonald Observatory of the University of Texas at Austin, of the Korean GMT Project of KASI, and Gemini Observatory. These results made use of the Lowell Discovery Telescope (LDT) at Lowell Observatory. Lowell is a private, non-profit institution dedicated to astrophysical research and public appreciation of astronomy and operates the LDT in partnership with Boston University, the University of Maryland, the University of Toledo, Northern Arizona University and Yale University. This paper includes data taken at The McDonald Observatory of The University of Texas at Austin. This work has made use of the VALD database, operated at Uppsala University, the Institute of Astronomy RAS in Moscow, and the University of Vienna.
Databáze: OpenAIRE
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