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Peer-reviewedCC BY 4.0Monthly Notices of the Royal Astronomical Society

Chemical abundances and kinematics of two very metal-poor stars: HE 1421+0022 and HE 2150−1800,

  • Jinturaj Talukdar1
  • Aruna Goswami2
  • Upakul Mahanta1
  1. 1Bhattadev University Department of Physics, , Bajali, Pathsala 781325 ,
  2. 2Indian Institute of Astrophysics , Koramangala, Bangalore 560034 ,
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Abstract

We present, for the first time, a detailed high-resolution spectroscopic analysis of two VMP stars, HE 1421+0022 and HE 2150−1800. Both stars exhibit significant carbon enhancement ([C/Fe] ≥+2.0)and enhanced nitrogen abundances ([N/Fe] ~+2.17 and +1.37 respectively). The derived metallicities, [Fe/H] ~−2.79 and −2.48, respectively, place both stars firmly in the VMP regime. We determined the abundances of the light and iron-peak elements C, N, Na, Mg, Ca, Sc, Ti, Cr, Mn, and Ni, as well as the neutron-capture elements Sr, Y, Zr, Ba, La, Ce, Pr, Nd, Sm, and Eu. Based on their locations both stars are classified as Group I objects in the Yoon-Beers diagram of A(C) vs [Fe/H]. Applying established classification criteria for carbon-enhanced metal-poor stars, HE 1421+0022 is identified as a CEMP-r/s star and HE 2150−1800 as a CEMP-s star. Our kinematic analysis shows that HE 1421+0022 is a high-energy, prograde star associated with the outer Galactic halo, while HE 2150−1800 is a high-energy, retrograde star associated with the inner halo. The combined chemodynamical properties suggest that HE 1421+0022 may be associated with either the Sagittarius (Sgr) or Gaia-Sausage/Enceladus (GSE) accretion event, whereas HE 2150−1800 is likely associated with the I’itoi structure. These results provide further evidence that metal-poor stars in the Galactic halo preserve signatures of accretion events involving dwarf satellite galaxies, offering valuable insights into the hierarchical assembly and chemical evolution of the Galaxy.

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Cite

BibTeXRIS
BibTeX
@article{talukdar2026chemical,
  title = {{Chemical abundances and kinematics of two very metal-poor stars: HE 1421+0022 and HE 2150−1800,}},
  author = {Jinturaj Talukdar and Aruna Goswami and Upakul Mahanta},
  journal = {Monthly Notices of the Royal Astronomical Society},
  year = {2026},
  month = oct,
  doi = {10.1093/mnras/stag1967},
  url = {https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stag1967/8923672},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
TI  - Chemical abundances and kinematics of two very metal-poor stars: HE 1421+0022 and HE 2150−1800,
AU  - Jinturaj Talukdar
AU  - Aruna Goswami
AU  - Upakul Mahanta
PY  - 2026
DA  - 2026/10/15
JO  - Monthly Notices of the Royal Astronomical Society
DO  - 10.1093/mnras/stag1967
UR  - https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stag1967/8923672
AB  - We present, for the first time, a detailed high-resolution spectroscopic analysis of two VMP stars, HE 1421+0022 and HE 2150−1800. Both stars exhibit significant carbon enhancement ([C/Fe] ≥+2.0)and enhanced nitrogen abundances ([N/Fe] ~+2.17 and +1.37 respectively). The derived metallicities, [Fe/H] ~−2.79 and −2.48, respectively, place both stars firmly in the VMP regime. We determined the abundances of the light and iron-peak elements C, N, Na, Mg, Ca, Sc, Ti, Cr, Mn, and Ni, as well as the neutron-capture elements Sr, Y, Zr, Ba, La, Ce, Pr, Nd, Sm, and Eu. Based on their locations both stars are classified as Group I objects in the Yoon-Beers diagram of A(C) vs [Fe/H]. Applying established classification criteria for carbon-enhanced metal-poor stars, HE 1421+0022 is identified as a CEMP-r/s star and HE 2150−1800 as a CEMP-s star. Our kinematic analysis shows that HE 1421+0022 is a high-energy, prograde star associated with the outer Galactic halo, while HE 2150−1800 is a high-energy, retrograde star associated with the inner halo. The combined chemodynamical properties suggest that HE 1421+0022 may be associated with either the Sagittarius (Sgr) or Gaia-Sausage/Enceladus (GSE) accretion event, whereas HE 2150−1800 is likely associated with the I’itoi structure. These results provide further evidence that metal-poor stars in the Galactic halo preserve signatures of accretion events involving dwarf satellite galaxies, offering valuable insights into the hierarchical assembly and chemical evolution of the Galaxy.
SN  - 0035-8711
SN  - 1365-2966
ER  -