A search for hydrogenated fullerenes in fullerene-containing planetary nebulae

¹ Instituto de Astrofísica de Canarias, C/ Via Láctea s/n, 38205 La Laguna, Spain
e-mail: jdiaz@iac.es; agarcia@iac.es
² Departamento de Astrofísica, Universidad de La Laguna (ULL), 38206 La Laguna, Spain
³ Consejo Superior de Investigaciones Científicas, Madrid, Spain
⁴ INAF–Osservatorio Astrofisico di Catania, via S. Sofia 78, 95123 Catania, Italy
⁵ Actinium Chemical Research srl, via Casilina 1626/A, 00133 Rome, Italy

Received: 11 November 2015
Accepted: 19 February 2016

Abstract

Detections of C₆₀ and C₇₀ fullerenes in planetary nebulae (PNe) of the Magellanic Clouds and of our own Galaxy have raised the idea that other forms of carbon, such as hydrogenated fullerenes (fulleranes like C₆₀H₃₆ and C₆₀H₁₈), buckyonions, and carbon nanotubes, may be widespread in the Universe. Here we present VLT/ISAAC spectra (R ~ 600) in the 2.9−4.1 μm spectral region for the Galactic PNe Tc 1 and M 1−20, which have been used to search for fullerene-based molecules in their fullerene-rich circumstellar environments. We report the non-detection of the most intense infrared bands of several fulleranes around ~3.4−3.6 μm in both PNe. We conclude that if fulleranes are present in the fullerene-containing circumstellar environments of these PNe, then they seem to be much less abundant than C₆₀ and C₇₀. Our non-detections, together with the (tentative) fulleranes detection in the proto-PN IRAS 01005+7910, suggest that fulleranes may be formed in the short transition phase between AGB stars and PNe, but they are quickly destroyed by the UV radiation field from the central star.