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First r -process enhanced star confirmed as a member of the Galactic bulge

Forsberg, R. LU ; Rich, R. M. ; Nieuwmunster, N. LU ; Jönsson, H. ; Schultheis, M. ; Ryde, N. LU orcid and Thorsbro, B. LU orcid (2023) In Astronomy and Astrophysics 669.
Abstract

Aims. Stars with strong enhancements of r-process elements are rare and tend to be metal-poor, generally with [Fe/H] < -2 dex, and located in the halo. In this work, we aim to investigate a candidate r-process enriched bulge star with a relatively high metallicity of [Fe/H] ~ -0.65 dex and to compare it with a previously published r-rich candidate star in the bulge. Methods. We reconsidered the abundance analysis of a high-resolution optical spectrum of the red-giant star 2MASS J18082459-2548444 and determined its europium (Eu) and molybdenum (Mo) abundance, using stellar parameters from five different previous studies. Applying 2MASS photometry, Gaia astrometry, and kinematics, we estimated the distance, orbits, and population... (More)

Aims. Stars with strong enhancements of r-process elements are rare and tend to be metal-poor, generally with [Fe/H] < -2 dex, and located in the halo. In this work, we aim to investigate a candidate r-process enriched bulge star with a relatively high metallicity of [Fe/H] ~ -0.65 dex and to compare it with a previously published r-rich candidate star in the bulge. Methods. We reconsidered the abundance analysis of a high-resolution optical spectrum of the red-giant star 2MASS J18082459-2548444 and determined its europium (Eu) and molybdenum (Mo) abundance, using stellar parameters from five different previous studies. Applying 2MASS photometry, Gaia astrometry, and kinematics, we estimated the distance, orbits, and population membership of 2MASS J18082459-2548444 and a previously reported r-enriched star 2MASS J18174532-3353235. Results. We find that 2MASS J18082459-2548444 is a relatively metal-rich, enriched r-process star that is enhanced in Eu and Mo, but not substantially enhanced in s-process elements. There is a high probability that it has a Galactic bulge membership, based on its distance and orbit. We find that both stars show r-process enhancement with elevated [Eu/Fe]-values, even though 2MASS J18174532-3353235 is 1 dex lower in metallicity. Additionally, we find that the plausible origins of 2MASS J18174532-3353235 to be either that of the halo or the thick disc. Conclusions. We conclude that 2MASS J18082459-2548444 represents the first example of a confirmed r-process enhanced star confined to the inner bulge. We assume it is possibly a relic from a period of enrichment associated with the formation of the bar.

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author
; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Galaxy: bulge, Galaxy: evolution, Stars: abundances, Stars: chemically peculiar
in
Astronomy and Astrophysics
volume
669
article number
A17
publisher
EDP Sciences
external identifiers
  • scopus:85145439684
ISSN
0004-6361
DOI
10.1051/0004-6361/202244305
language
English
LU publication?
yes
id
d4292220-e972-4492-a42f-be1a6efe6929
date added to LUP
2023-02-13 13:09:48
date last changed
2023-09-11 13:10:46
@article{d4292220-e972-4492-a42f-be1a6efe6929,
  abstract     = {{<p>Aims. Stars with strong enhancements of r-process elements are rare and tend to be metal-poor, generally with [Fe/H] &lt; -2 dex, and located in the halo. In this work, we aim to investigate a candidate r-process enriched bulge star with a relatively high metallicity of [Fe/H] ~ -0.65 dex and to compare it with a previously published r-rich candidate star in the bulge. Methods. We reconsidered the abundance analysis of a high-resolution optical spectrum of the red-giant star 2MASS J18082459-2548444 and determined its europium (Eu) and molybdenum (Mo) abundance, using stellar parameters from five different previous studies. Applying 2MASS photometry, Gaia astrometry, and kinematics, we estimated the distance, orbits, and population membership of 2MASS J18082459-2548444 and a previously reported r-enriched star 2MASS J18174532-3353235. Results. We find that 2MASS J18082459-2548444 is a relatively metal-rich, enriched r-process star that is enhanced in Eu and Mo, but not substantially enhanced in s-process elements. There is a high probability that it has a Galactic bulge membership, based on its distance and orbit. We find that both stars show r-process enhancement with elevated [Eu/Fe]-values, even though 2MASS J18174532-3353235 is 1 dex lower in metallicity. Additionally, we find that the plausible origins of 2MASS J18174532-3353235 to be either that of the halo or the thick disc. Conclusions. We conclude that 2MASS J18082459-2548444 represents the first example of a confirmed r-process enhanced star confined to the inner bulge. We assume it is possibly a relic from a period of enrichment associated with the formation of the bar.</p>}},
  author       = {{Forsberg, R. and Rich, R. M. and Nieuwmunster, N. and Jönsson, H. and Schultheis, M. and Ryde, N. and Thorsbro, B.}},
  issn         = {{0004-6361}},
  keywords     = {{Galaxy: bulge; Galaxy: evolution; Stars: abundances; Stars: chemically peculiar}},
  language     = {{eng}},
  month        = {{01}},
  publisher    = {{EDP Sciences}},
  series       = {{Astronomy and Astrophysics}},
  title        = {{First r -process enhanced star confirmed as a member of the Galactic bulge}},
  url          = {{http://dx.doi.org/10.1051/0004-6361/202244305}},
  doi          = {{10.1051/0004-6361/202244305}},
  volume       = {{669}},
  year         = {{2023}},
}