A New Identification of the 6.2, 7.7 and 8.5 µm Circumstellar Emission Features with Oxidized QCC

Abstract

The unidentified infrared (UIR) emission bands constitute a family of emission features at 3.3, 3.4, 6.2, 7.7, 8.6, and 11.3 µm (Aitken, 1981; Barlow, 1983; Willner, 1984). Recently new features at 5.6 and 6.9 µm (Bregman et al., 1983; Cohen et al., 1986) and those at 3.46 and 3.52 µm (de Muizon et al., 1986; Nagata et al., 1987) as well as a plateau between 11.3 and 13.0 µm (Cohen et al., 1985) have been added to the family. A broad feature seen between 5.5 and 9.6 µm must also be related to the UIR emission bands (Seligren et al., 1985; Cohen et al., 1986). No fine structure have been detected in the three µm features, indicating that they are solid state in origin (Tokunaga and Young, 1980). Latest observations indicate the absence of the 3.4 µm feature in an object emitting the 3.3 µm feature together with the variation of the width and the position of the 3.3 µm feature in some objects (Nagata et al., 1987; Tokunaga et al., 1987). There has been accumulating evidence for the carbonaceous origin of these features and attempts have been made to interpret all the features in terms of only carbon and hydrogen bonds of poly cyclic aromatic hydrocarbons (PAHs) (Léger and Puget, 1984; Allamandola et al., 1985).