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| Author(s): |
Vinicius Moris Placco
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto Astronômico e Geofísico (IAG/SBD) |
| Defense date: | 2010-08-31 |
| Examining board members: |
Silvia Cristina Fernandes Rossi;
Timothy Carter Beers;
Alan Alves Brito;
Roberto Dell' Aglio Dias da Costa;
Jorge Luis Melendez Moreno
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| Advisor: | Silvia Cristina Fernandes Rossi |
| Abstract | |
The main goal of this work is to show that is possible to search for metal-poor stars based on the premise that a large fraction of these will be carbon-rich. This hypothesis had not yet been verified because many of the so-called CEMP (Carbon Enhanced Metal-Poor) stars were neglected in previous studies due to the design of the search for metal-poor stars with carbon enhancements. Those objects play a major role as fossil records of the very first generation of stars, since they carry in their atmospheres vital informations concerning the chemical composition of the medium where they were formed. By not showing strong carbon molecular bands in their spectra, many of those stars were not selected for follow-up studies in medium/high resolution. This work provides, based on the study of the stellar part of the HES (Hamburg/ESO Survey), two new line indices for the G band (4304 Å) that, by having a line band of 200 Å, can overcome the flaws of the previously defined indices and also truly represent the main features of this region. After an extensive analysis of the database and the calculation of the line indices for all the available objects, 132 new metal-poor stars were identified with the SOAR telescope, being that 51% of those stars with [Fe/H] < 1.0 present considerable carbon enhancements ([C/Fe]> +0.5). For the observed stars with [Fe/H] < 2.5, the fraction of objects with [C/Fe] > +1.0 rises up to 80%. Abundance estimates for barium and strontium show that, even with similar atmospheric parameters and carbon abundances, the stars analysed in this work have more than one possible formation scenario. Finally, this work also contributes with a 6123 CEMP star candidate list of unpublished objects. (AU) | |
| FAPESP's process: | 07/04356-3 - Search for carbon enhanced metal-poor stars |
| Grantee: | Vinicius Moris Placco |
| Support Opportunities: | Scholarships in Brazil - Doctorate |