Identification of more interstellar C60+ bands

TL;DR

This study confirms the presence of interstellar C60+ fullerene ions by detecting specific diffuse interstellar bands (DIBs) in stellar spectra, supporting their role as DIB carriers with improved observational techniques.

Contribution

The paper provides new observational evidence for C60+ as a DIB carrier by detecting previously ambiguous bands using advanced telluric correction methods.

Findings

Detection of DIB at 9365.9A consistent with laboratory spectra.

Identification of DIB at 9362.5A matching laboratory data.

Clear detection of 9428.5A DIB in a suitable archival spectrum.

Abstract

Based on gas-phase laboratory spectra at 6 K, Campbell et al. (2015) confirmed that the diffuse interstellar bands (DIBs) at 9632.7 and 9577.5A are due to absorption by the fullerene ion C60+. They also reported the detection of two other, weaker bands at 9428.5 and 9365.9A. These lie in spectral regions heavily contaminated by telluric water vapour lines. We acquired CFHT ESPaDOnS spectra of HD183143 close to the zenith and chopped with a nearby standard to correct for the telluric line absorption which enabled us to detect a DIB at 9365.9A of relative width and strength comparable to the laboratory absorption. There is a DIB of similar strength and FWHM at 9362.5A. A stellar emission feature at 9429A prevented detection of the 9428.5A band. However, a CFHT archival spectrum of HD169454, where emission is absent at 9429A, clearly shows the 9428.5A DIB with the expected strength and width. These results further confirm C60+ as a DIB carrier.