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| Main Authors: | , |
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| Format: | Preprint |
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2024
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| Online Access: | https://arxiv.org/abs/2412.12792 |
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| _version_ | 1866929690686521344 |
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| author | Saini, Ajay Kumar Pandey, Gajendra |
| author_facet | Saini, Ajay Kumar Pandey, Gajendra |
| contents | A fine abundance analysis of a recently discovered hydrogen-deficient carbon (HdC) star, A 980, is presented. Based on the observed high-resolution optical spectrum, we ascertain that A 980 is a cool extreme helium (EHe) star and not an HdC. Singly-ionized germanium Ge II lines are identified in A 980's optical spectrum. These are the first-ever detections of germanium lines in an EHe's observed spectrum, and provide the first measurements of germanium abundance in an EHe star. The overabundance of germanium in A 980's atmosphere provides us with evidence for the synthesis of germanium in EHe stars. Among the known cool EHe stars, A 980 exhibits a maximum enhancement of the s-process elements based on significant number of transitions. The measured elemental abundances reveal signs of H-burning, He-burning, and specifically the nucleosyntheses of the key elements: Ge, Sr, Y, Zr, and Ba. The nucleosyntheses of these key elements are discussed in light of asymptotic giant branch evolution and the expectation from the accretion of an He white dwarf by a C-O white dwarf or by a neutron star. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2412_12792 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Detection of Enhanced Germanium in a New Cool Extreme Helium Star A 980: Insights and Implications Saini, Ajay Kumar Pandey, Gajendra Solar and Stellar Astrophysics A fine abundance analysis of a recently discovered hydrogen-deficient carbon (HdC) star, A 980, is presented. Based on the observed high-resolution optical spectrum, we ascertain that A 980 is a cool extreme helium (EHe) star and not an HdC. Singly-ionized germanium Ge II lines are identified in A 980's optical spectrum. These are the first-ever detections of germanium lines in an EHe's observed spectrum, and provide the first measurements of germanium abundance in an EHe star. The overabundance of germanium in A 980's atmosphere provides us with evidence for the synthesis of germanium in EHe stars. Among the known cool EHe stars, A 980 exhibits a maximum enhancement of the s-process elements based on significant number of transitions. The measured elemental abundances reveal signs of H-burning, He-burning, and specifically the nucleosyntheses of the key elements: Ge, Sr, Y, Zr, and Ba. The nucleosyntheses of these key elements are discussed in light of asymptotic giant branch evolution and the expectation from the accretion of an He white dwarf by a C-O white dwarf or by a neutron star. |
| title | Detection of Enhanced Germanium in a New Cool Extreme Helium Star A 980: Insights and Implications |
| topic | Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2412.12792 |