Elemental abundances of metal poor carbon rich lead star: CS29497-030

T. Sivarani; P. Bonifacio; P. Molaro; R. Cayrel; M. Spite; F. Spite; B. Plez; J. Andersen; B. Barbuy; T. C. Beers; E. Depagne; V. Hill; P. Francois; B. Nordstrom; F. Primas

arXiv · astro-ph/0212406

Elemental abundances of metal poor carbon rich lead star: CS29497-030

T. Sivarani·P. Bonifacio·P. Molaro·R. Cayrel·M. Spite·F. Spite·B. Plez·J. Andersen·B. Barbuy·T. C. Beers·E. Depagne·V. Hill·P. Francois·B. Nordstrom·F. Primas

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Abstract

We present here the abundance analysis of a metal poor carbon rich lead star, CS29497-030. High resolution and high signal to noise spectra were obtained using the UVES spectrograph on the 8.2m VLT-Kueyen telescope. The observations were made as a part of the Large Programme 165.N-0276, P.I. R. Cayrel. Abundance analysis was done using the latest version of the MARCS model atmospheres (Plez et. al. 1992) and the turbospectrum spectrum synthesis code. We have derived Teff = 6650K from the FeI lines. Visible and infrared broad band colours using the Alonso et al. (1996) calibration, gives similar temperatures. A log g value of 3.5 was obtained from the ionisation equilibrium of FeI and FeII, we remark that this gravity also satisfies the MgI/MgII, TiI/TiII and MnI/MnII equilibria, within errors. The abundance analysis indicates a metallicity, [Fe/H] = --2.7. A large overabundance of carbon ([C/Fe]=2.7) was found. We have also found large enhancement in the s-process elements and in particular lead shows an extremely high abundance of [Pb/Fe]=3.5, which makes this the star with the highest Pb/Fe ratio, up to date. The Pb/Ba ratio is found to be high ([Pb/Ba]=1.2) and the same s true for other second-peak s-process elements(e.g La, Ce, Nd). The star is a known spectroscopic binary with a period of 346 days (Preston & Sneden 2000). The abundance pattern suggests that CS 29497-30 has accreted matter from its companion, when it was in the AGB phase.

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T. Sivarani, P. Bonifacio, P. Molaro, R. Cayrel, M. Spite, F. Spite, B. Plez, J. Andersen, B. Barbuy, T. C. Beers, E. Depagne, V. Hill, P. Francois, B. Nordstrom, F. Primas. 2002-12-18. Elemental abundances of metal poor carbon rich lead star: CS29497-030. https://arxiv.org/abs/astro-ph/0212406

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