Cassiopeia A dust composition and heating

Material ejected by a supernova is directly observed in the form of Fast Moving Knots (FMK's) in the Cassiopeia A supernova remnant. Part of this material has condensed into dust. In this paper, by tting the ISO mid-infrared emission of the dust, we derive the dust composition and discuss the dust heating. The dust is found to be made mainly of three components: pyroxene, quartz and aluminium oxide. These components have to be heated at two dierent temperatures, a \hot" temperature around 350 K and a cold temperature around 90 K. The physical conditions in the knot-shocked region are such that the dust can be collisionally heated to a temperature of 350 K. The cold dust temperature can also be well accounted for by the knot model discussed in the paper. The dust formation eciency is tentatively estimated to be of the order of 10% in this supernova.