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19 April 2024 |
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HE0107-5240, A Chemically Ancient Star.I. A Detailed Abundance Analysis | | N. Christlieb
; B. Gustafsson
; A. J. Korn
; P. S. Barklem
; T. C. Beers
; M. S. Bessell
; T. Karlsson
; M. Mizuno-Wiedner
; | | Date: |
7 Nov 2003 | | Journal: | Astrophys.J. 603 (2004) 708-728 | | Subject: | astro-ph | | Affiliation: | Uppsala Astronomical Observatory and Hamburger Sternwarte), B. Gustafsson (Uppsala Astronomical Observatory), A. J. Korn (Universitaets-Sternwarte Muenchen and Uppsala Astronomical Observatory), P. S. Barklem (Uppsala Astronomical Observatory), T. C. B | | Abstract: | We report a detailed abundance analysis for HE0107-5240, a halo giant with [Fe/H]_NLTE=-5.3. This star was discovered in the course of follow-up medium-resolution spectroscopy of extremely metal-poor candidates selected from the digitized Hamburg/ESO objective-prism survey. On the basis of high-resolution VLT/UVES spectra, we derive abundances for 8 elements (C, N, Na, Mg, Ca, Ti, Fe, and Ni), and upper limits for another 12 elements. A plane-parallel LTE model atmosphere has been specifically tailored for the chemical composition of {he}. Scenarios for the origin of the abundance pattern observed in the star are discussed. We argue that HE0107-5240 is most likely not a post-AGB star, and that the extremely low abundances of the iron-peak, and other elements, are not due to selective dust depletion. The abundance pattern of HE0107-5240 can be explained by pre-enrichment from a zero-metallicity type-II supernova of 20-25M_Sun, plus either self-enrichment with C and N, or production of these elements in the AGB phase of a formerly more massive companion, which is now a white dwarf. However, significant radial velocity variations have not been detected within the 52 days covered by our moderate-and high-resolution spectra. Alternatively, the abundance pattern can be explained by enrichment of the gas cloud from which HE0107-5240 formed by a 25M_Sun first-generation star exploding as a subluminous SNII, as proposed by Umeda & Nomoto (2003). We discuss consequences of the existence of HE0107-5240 for low-mass star formation in extremely metal-poor environments, and for currently ongoing and future searches for the most metal-poor stars in the Galaxy. | | Source: | arXiv, astro-ph/0311173 | | Services: | Forum | Review | PDF | Favorites | |
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