The Infrared Emission Features in the Spectrum of the Wolf-Rayet star WR 48[CLC]a[/CLC]

Abstract

We present the first detection of unidentified infrared (UIR) emissionfeatures at ~6.4 and 7.9 {μ}m in the spectrum of the dusty WC8Wolf-Rayet star WR 48a. Based on the H-deficient nature of WC stars, weattribute the emission features to large carbonaceous molecules oramorphous carbon dust grains in the circumstellar environment of WR 48a.The 6.4 {μ}m feature resembles the emission feature seen towardH-deficient planetary nebulae (PNe), while the 7.9 {μ}m profileresembles that of some PNe with H-deficient WC10 central stars. Thesesimilarities point toward a similar origin of the dust in theseH-deficient environments and highlights the apparent sensitivity of theUIR bands to physical conditions. In the case of WR 48a and the [WC10]PNe, shock processing may play a major role in dust formation. Based onobservations made with the Infrared Space Observatory, an ESA projectwith instruments funded by ESA member states (especially the PIcountries: France, Germany, the Netherlands, and the United Kingdom) andwith the participation of ISAS and NASA.