High-resolution optical spectroscopy of DY Cen: diffuse interstellar bands in a proto-fullerene circumstellar environment?

摘要

We search high-resolution and high-quality VLT/UVES optical spectra of thehot R Coronae Borealis (RCB) star DY Cen for electronic transitions of the C60molecule and diffuse interstellar bands (DIBs). We report the non-detection ofthe strongest C60 electronic transitions (e.g., those at ~3760, 3980, and 4024A). Absence of C60 absorption bands may support recent laboratory results,which show that the ~7.0, 8.5, 17.4, and 18.8 um emission features seen in DYCen - and other similar objects with PAH-like dominated IR spectra - areattributable to proto-fullerenes or fullerene precursors rather than to C60.DIBs towards DY Cen are normal for its reddening; the only exception is the DIBat 6284 A (possibly also the 7223A DIB) that is found to be unusually strong.We also report the detection of a new broad (FWHM~2 A) and unidentified featurecentered at ~4000 A. We suggest that this new band may be related to thecircumstellar proto-fullerenes seen at infrared wavelengths.