Other
Scientific paper
Aug 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003basbr..23...90a&link_type=abstract
Boletim da Sociedade Astronômica Brasileira (ISSN 0101-3440), vol.23, no.1, p. 90-90
Other
Scientific paper
The metallicity of Post-T Tauri stars (PTTS) associations is unknown. The knowledge of this parameter in these stars where planets are probably forming around them, could shed some light to this problem. Why a large part of stars harboring planets are metal rich? Two main and different approaches have been proposed 1) The cloud that gave origin to these stars was already metal enriched (original hypothesis) 2) Stars contamination by the bombarding of solid metal planetesimals coming from their rocky disk. In fact, PTTS are in an ideal evolutionary stage to test the two mechanisms mentioned above. If all members of an association present a similar metallicity, this will favor the original hypothesis. Now, if hotter G stars exhibit larger metal abundance than the cooler K - M stars of the same association this will favor the contamination hypothesis. This is because the smaller convective layers of hotter and more massive G stars will maintain any new solid metal injections, whereas this is not the case of cool K - M stars with their large convective zones. Because we don't know the moment when this eventual bombarding is being made, we will consider two different association to test this hypothesis. Two recent discovered associations resulting from the Search for Association Contaning Young stars (SACY) are being used. These are: GAYA (Great Austral Young Association) with an age of 30 Myr and YSSA (Young Sagitarius Scorpius Association) with an age of 8 Myr. Metallic Abundance calculations for all stars are made by selecting lines of Fe and Si from high resolution FEROS spectra. Because stellar rotation can introduce some limitations due to blending effects, we choose stars with the lowest rotation velocities as possible. Using 13 stars belonging to GAYA we found a clear tendency of increasing metallicity for high temperature stars indicating the action of the contamination mechanism. But, before accepting this trend as a fact, we must be sure that here is no bias introduced on it by any other stellar characteristic, like rotation velocity, for example.
Almeida Ricardo
da Silva Loureiro L.
de La Reza Ramiro
Oliveira Isa
Quast Germano
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