Diffuse interstellar bands in fullerene planetary nebulae: the fullerenes - diffuse interstellar bands connection

Abstract

We present high-resolution (R~15000) VLT/UVES optical spectra of two planetary nebulae (PNe; Tc 1 and M 1-20) where C60 (and C70) fullerenes have already been found. These spectra are of high-quality (S/N > 300) for PN Tc 1, which permits us to search for the expected electronic transitions of neutral C60 and diffuse interstellar bands (DIBs). Surprisingly, we report the non-detection of the most intense optical bands of C60 in Tc 1, although this could be explained by the low C60 column density estimated from the C60 infrared bands if the C60 emission peaks far away from the central star. The strongest and most common DIBs in both fullerene PNe are normal for their reddening. Interestingly, the very broad 4428 A DIB and the weaker 6309 A DIB are found to be unusually intense in Tc 1. We also report the detection of a new broad (FWHM~5 A) unidentified band at ~6525 A. We propose that the 4428 A DIB (probably also the 6309 A DIB and the new 6525 A band) may be related to the presence of larger fullerenes (e.g., C80, C240, C320, and C540) and buckyonions (multishell fullerenes such as C60@C240 and C60@C240@C540) in the circumstellar envelope of Tc 1.

Accepted for publication in Astronomy & Astrophysics Letters (6 pages, 4 figures, and 1 Table)

References in corpus (10)

• A Catalog of Diffuse Interstellar Bands in the Spectrum of HD 204827
• Formation of fullerenes in H-containing Planetary Nebulae
• Infrared Study of Fullerene Planetary Nebulae
• On the Excitation and Formation of Circumstellar Fullerenes
• The formation of cosmic fullerenes from arophatic clusters
• Elemental abundances of Galactic bulge planetary nebulae from optical recombination lines
• The VLT-FLAMES Tarantula Survey. IX. The interstellar medium seen through Diffuse Interstellar Bands and neutral sodium
• A search for diffuse bands in the circumstellar envelopes of post-AGB stars
• Independent Emission and Absorption Abundances for Planetary Nebulae
• High-resolution optical spectroscopy of DY Cen: diffuse interstellar bands in a proto-fullerene circumstellar environment?

Cited by in corpus (10)

• Mapping the Interstellar Medium with Near-Infrared Diffuse Interstellar Bands
• Infrared spectroscopy of fullerene C60/anthracene adducts
• A search for diffuse bands in fullerene planetary nebulae: evidence of diffuse circumstellar bands
• C60 as a probe for astrophysical environments
• Are the Carriers of Diffuse Interstellar Bands and Extended Red Emission the same?
• A search for hydrogenated fullerenes in fullerene-containing planetary nebulae
• A young multipolar planetary nebula in the making: IRAS 21282+5050
• An Infrared Diffuse Circumstellar Band? The Unusual 1.5272 Micron DIB In the Red Square Nebula
• The C60:C60+ ratio in diffuse and translucent interstellar clouds
• On the formation of molecules and solid-state compounds from the AGB to the PN phases