The anomalous infrared emission of Abell 58

We present a new model to explain the excess in mid- and near-infrared emis sion of the central, hydrogen-poor dust knot in the planetary nebula (PN) A bell 58. Current models disagree with ISO measurements because they apply a n average grain size and equilibrium conditions only. We investigate grain size distributions and temperature fluctuations affecting infrared emission using a new radiative transfer code and discuss in detail the conditions r equiring an extension of the classical description. The peculiar infrared e mission of V605 Aql, the central dust knot in Abell 58, has been modeled wi th our code. V605 Aql is of special interest as it is one of only three sta rs ever observed to move from the evolutionary track of a central PN star b ack to the post-asymptotic giant branch state.