Cassiopeia A dust composition and heating

Material ejected by a supernova is directly observed in the form of Fast Mo ving Knots (FMK's) in the Cassiopeia A supernova remnant. Part of this mate rial has condensed into dust. In this paper, by fitting the ISO mid-infrare d 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 dif ferent temperatures, a "hot" temperature around 350 E; and a cold temperatu re 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 c old dust temperature can also be well accounted for by the knot model discu ssed in the paper. The dust formation efficiency is tentatively estimated t o be of the order of 10% in this supernova.