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Chemical composition of carbon-rich, very metal-poor subgiant LP625-44 observed with the Subaru/HDS | W. Aoki
; H. Ando
; S. Honda
; M. Iye
; H. Izumiura
; T. Kajino
; E. Kambe
; S. Kawanomoto
; K. Noguchi
; K. Okita
; K. Sadakane
; B. Sato
; I. Shelton
; M. Takada-Hidai
; Y. Takeda
; E. Watanabe
; M. Yoshida
; | Date: |
8 Apr 2002 | Subject: | astro-ph | Abstract: | We have obtained a high resolution (R~90,000) spectrum of the carbon- and s-process-element-rich, very metal-poor ([Fe/H]=-2.7) subgiant LP625-44, as well as that of HD140283 (a metal-poor subgiant with normal abundance ratio) for comparison, with the High Dispersion Spectrograph (HDS) for the Subaru Telescope for detailed abundance study. The oxygen abundance derived from the O I triplet around 7770A is uncertain, but the excess of oxygen in LP625-44 seems remarkable (perhaps by nearly a factor 10), in comparison with that of HD140283 derived from the same lines. The Na enhancement in LP625-44 is by about a factor 50, suggesting hydrogen burning in the 22Ne-rich layer in an asymptotic giant branch star which produces the abundance pattern of this object. In our new spectrum of LP625-44, the Pb I lambda 3683A line has been detected, as well as the Pb I lambda 4057A line which has already been studied, confirming the Pb abundance (log epsilon(Pb)~1.9) derived by the previous work. The abundance ratio of s-process elements at the second peak (e.g., La, Ce and Nd) to that at the third peak (Pb) in LP 625-44 is significantly higher (by a factor 5) than that in other three s-process element-rich objects recently studied by van Eck et al.. Recent theoretical works have modeled the s-process nucleosynthesis in the radiative layer of asymptotic giant branch stars in the inter-pulse phase, and the above results means that these processes produced a large scatter in the abundance ratios. Another possiblity is that different processes (e.g., s-process nucleosynthesis during thermal pulses) have contributed to heavy elements in the early Galaxy. | Source: | arXiv, astro-ph/0204117 | Services: | Forum | Review | PDF | Favorites |
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