Browsing by Author "Spite, M."

Now showing 1 - 3 of 3
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    Clues on the Galactic evolution of sulphur from star clusters
    (2014) Caffau, E.; Monaco, L.; Spite, M.; Bonifacio, P.; Carraro, G.; Ludwig, H. -G.; Villanova, S.; Beletsky, Y.; Sbordone, L.
    Context. The abundances of a-elements are a powerful diagnostic of the star formation history and chemical evolution of a galaxy. Sulphur. being moderately volatile, can be reliably measured in the interstellar medium (ISM) of damped Ly-alpha galaxies and extragalactic H-II regions. Measurements in stars of different metallicity in our Galaxy can then be readily compared to the abundances in external galaxies. Such a comparison is not possible for Si or Ca that suffer depletion onto dust in the ISM. Furthermore, studying sulphur is interesting because it probes nucleosynthetic conditions that are very different from those of Oar Mg. In this context measurements in star clusters are a reliable tracers of the Galactic evolution of sulphur.
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    The low Sr/Ba ratio on some extremely metal-poor stars
    (2014) Spite, M.; Spite, F.; Bonifacio, P.; Caffau, E.; Francois, P.; Sbordone, L.
    Context. It has been noted that, in classical extremely metal-poor (EMP) stars, the abundance ratio of two well-observed neutron-capture elements, Sr and Ba, is always higher than [Sr/Ba] = -0.5, which is the value of the solar r-only process; however, a handful of EMP stars have recently been found with a very low Sr/Ba ratio.
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    TOPoS II. On the bimodality of carbon abundance in CEMP stars Implications on the early chemical evolution of galaxies
    (EDP SCIENCES S A, 2015) Bonifacio, P.; Caffau, E.; Spite, M.; Limongi, M.; Chieffi, A.; Klessen, R. S.; Francois, P.; Molaro, P.; Ludwig, H. G.; Zaggia, S.; Spite, F.; Plez, B.; Cayrel, R.; Christlieb, N.; Clark, P. C.; Glover, S. C. O.; Hammer, F.; Koch, A.; Monaco, L.; Sbordone, L.; Steffen, M.
    Context. In the course of the Turn Off Primordial Stars (TOPoS) survey, aimed at discovering the lowest metallicity stars, we have found several carbon-enhanced metal-poor (CEMP) stars. These stars are very common among the stars of extremely low metallicity and provide important clues to the star formation processes. We here present our analysis of six CEMP stars.