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20 April 2024 |
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Stellar Archaeology: a Keck Pilot Program on Extremely Metal- Poor Stars From the Hamburg/ESO Survey. III. The Lead (Pb) Star HE 0024-2523 | | Sara Lucatello
; Raffaele Gratton
; Judith G. Cohen
; Timothy C. Beers
; Norbert Christlieb
; Eugenio Carretta
; Solange Ramirez
; | | Date: |
4 Nov 2002 | | Subject: | astro-ph | | Affiliation: | 1,2), Raffaele Gratton , Judith G. Cohen , Timothy C. Beers , Norbert Christlieb , Eugenio Carretta and Solange Ramirez ( INAF - Osservatorio Astronomico di Padova, Italy, Astronomy Department, University of Padova, Palomar Observatory, Caltech, P | | Abstract: | We present a detailed abundance analysis, including spectral syntheses, of a very metal-poor ([Fe/H]= -2.7), peculiar main sequence star, HE0024-2523 detected during the course of the Keck Pilot Program. Radial velocities of this star were obtained during four different observing runs over a time span of 1.1 years, and demonstrate that it is clearly a short period spectroscopic binary. An orbital solution was obtained, and orbital parameters were determined with high precision. The rotational velocity was also measured (vsin i=9.7$pm$1.5 kms); rotation appears likely to be synchronous with the orbit. The abundance analysis and spectral syntheses indicate that the object is a CH star characterized by extreme s-process enrichment, likely due to mass accretion from an evolved companion which has now probably become a white dwarf. The lead (Pb) abundance of HE0024-2523 is very high, the same as that of the recently discovered lead-rich metal-poor star CS 29526-110, [Pb/Fe]=+3.3. The abundance ratio of the heavy-s to light-s elements, as characterized by Pb and Ba, [Pb/Ba]=+1.9, is the highest yet found for any metal-poor star, and is about 0.7 dex higher than that of CS29526-110. On the basis of the measured isotopic ratio of carbon (12C/13C about 6) we argue that the mass donor must have had an original mass of at least 3 Msun. The unusually short period of this CH star suggests that it underwent a past common-envelope phase with its evolved companion. Our results are compared to the latest available models for AGB yields and s-process nucleosynthesis. We also discuss the possible connection between HE0024-2523 the lithium depletion of halo stars, and halo blue straggler formation. | | Source: | arXiv, astro-ph/0211050 | | Services: | Forum | Review | PDF | Favorites | |
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