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

TL;DR

This study uses high-resolution optical spectra of DY Cen to investigate the presence of C60 molecules and diffuse interstellar bands, finding no C60 detection but identifying a new potential proto-fullerene feature.

Contribution

The paper provides the first high-resolution optical spectral analysis of DY Cen focusing on C60 and DIBs, suggesting proto-fullerenes rather than C60 are present.

Findings

No detection of C60 electronic transitions.

DIBs are typical except for an unusually strong 6284 A band.

Discovery of a new broad feature at ~4000 A possibly related to proto-fullerenes.

Abstract

We search high-resolution and high-quality VLT/UVES optical spectra of the hot R Coronae Borealis (RCB) star DY Cen for electronic transitions of the C60 molecule and diffuse interstellar bands (DIBs). We report the non-detection of the strongest C60 electronic transitions (e.g., those at ~3760, 3980, and 4024 A). 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 DY Cen - and other similar objects with PAH-like dominated IR spectra - are attributable to proto-fullerenes or fullerene precursors rather than to C60. DIBs towards DY Cen are normal for its reddening; the only exception is the DIB at 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 feature centered at ~4000 A. We suggest that this new band may be related to the circumstellar proto-fullerenes seen at infrared wavelengths.