Publication Date:
2016-12-25
Description:
The laboratory gas-phase spectrum recently published by Campbell et al. has reinvigorated attempts to confirm the presence of the C $_{60}^+$ cation in the interstellar medium, through an analysis of the spectra of hot, reddened stars. This search is hindered by at least two issues that need to be addressed: (i) the wavelength range of interest is severely polluted by strong water-vapour lines coming from the Earth's atmosphere; (ii) one of the major bands attributed to C $_{60}^+$ , at 9633 Å, is blended with the stellar Mg ii line, which is susceptible to non-local thermodynamic equilibrium effects in hot stellar atmospheres. Both these issues are carefully considered here for the first time, based on high-resolution and high signal-to-noise ratio echellé spectra for 19 lines of sight. The result is that the presence of C $_{60}^+$ in interstellar clouds is brought into question.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
