Seminar @ DF-AS - P. Bonifacio - Carbon enhanced metal-poor stars: new insights from the TOPoS project

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05/06/2015 - 11:30
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05/06/2015 - 12:30
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It has been known for the last twenty years, among metal-poor stars the farction of carbon-enhanced metal poor stars  (CEMP, [C/Fe]> +1) increases with decreasing metallicity. I will present new results from the TOPoS project, including three newly discovered CEMP stars with metallicity below -4.5, rasing to a total of nine the known metal-poor stars in this metallicity regime. Eight out of nine of these stars are CEMP.  Five of these nine stars are unevolved (TO or SGB) and only one has a measured Li abundance, about 0.4 dex below the Spite plateau. A low lithium abundance seems to be a general characteristic of these stars. Another striking characteristic of the extremely metal-poor stars is the very low scatter in the [X/Ca] ratios for all elements heavier than Si, in spite of the fact that they span 3 orders of magnitude in Fe (or Ca) abundance. Our proposed scenario for the formation of the first generations of stars, is the formation of several massive stars in a mini-halo, at least one of which should explode as a faint supernova, to produce the excess carbon. I will finally discuss future perspectives for the search of and analysis of EMP stars.


Villa Bazzoni

Paolo Molaro
Last update: 05-04-2015 - 10:41