Other
Scientific paper
Feb 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002noao.prop..241k&link_type=abstract
NOAO Proposal ID #2002A-0241
Other
Scientific paper
Ap stars present high abundance of rare earth elements. These overabundances are understood as the result of radiative diffusion. In the model, the rare earth elements are pushed to the surface by selective radiation pressure because the wavelength where the radiation field is maximum is the same as the wavelength where the rare earths opacities peak. Radiation pressure is helped by the lack of convection in A star envelopes and by the inhibition of turbulence promoted by the magnetic fields. One fundamental question in the investigation of Ap stars is when, in the evolution process does an A star turn into an Ap star?. Previous work by Abt (1979) and Abt and Cardona (1983) have suggested that A stars turned into Ap stars as they aged. Later, other workers have questioned this result (see for instance North, 1993). All of the work done after Abt and Cardona was done based on photometric data rather than spectroscopy. Our goal is to solve this controversy using modern data based in spectra taken with higher resolution and signal to noise than Abt and Cardona's data. Furthermore, we plan to take all spectra with the same resolution and signal to noise - actually using the same equipment - therefore avoiding systematic effects in the classification process.
Fraga Luciano
Kanaan Antonio
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