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Projeto Observacional para 2008B - OI2008B-025

Instituição: UFSC
e-mail: kanaan@astro.ufsc.br

S. thompson
Paulo Henrique S. de Santana
Caroline Deggerone

Título: Measuring the surface inhomogeneity of Calcium on G29-38

Resumo: In the last three years a handful of white dwarfs (WDs) with circumstellar debris disks have been discovered. The debris disks are either left over from the late stages of stellar evolution or are the result of tidally disrupted asteroids or comets, and are the signposts of planetary systems. At present, we do not understand the accretion process, even at the basic level of whether magnetic fields channel the accreting material onto the star or the physical thickness of the disk. > >The pulsating WD G29-38 is the prototype debris disk WD; it is the brightest such WD known and has the most pronounced IR excess. We plan to take advantage of the pulsations of G29-38 to measure the surface inhomegeneities of calcium in G29-38. Due to the short timescale of gravitational settling as compared to horizontal mixing, we expect a larger abundance of calcium at the latitude of accretion from the debris disk. This will be the first test of chemical inhomogeneity due to non-spherical accretion and it will constrain the geometry and size of the inner debris disk.