Asteroseismology of the ZZ Ceti and DAZ GD133

GD 133 is a DAZ white dwarf with an atmosphere polluted by heavy elements accreted from a debris disk, which is formed by the disruption of rocky planetesimals with orbits bringing them at the white dwarf tidal radius. To reach such orbits implies the potential presence of a perturbing planet. GD133 is a ZZ Ceti pulsator close to the blue edge of the instability strip. The presence of a planet could be revealed by the periodical variation of the observed pulsation periods induced by the orbital motion of the white dwarf. We started a multi-site photometric follow-up aimed at detecting the signature of this potential planet. As a partial result of this work in progress, we give the parameters of a preliminary best-fit model derived from asteroseismology.