  Ever since their first detection over 100 years ago, the mysterious diffuse
interstellar bands (DIBs), a set of several hundred broad absorption features
seen against distant stars in the optical and near infrared wavelength range,
largely remain unidentified. The close match both in wavelengths and in
relative strengths recently found between the experimental absorption spectra
of gas-phase buckminsterfullerene ions (C60+) and four DIBs at 9632, 9577, 9428
and 9365 Angstrom (and, to a lesser degree, a weaker DIB at 9348 Angstrom)
suggests C60+ as a promising carrier. However, arguments against the C60+
identification remain and are mostly concerned with the large variation in the
intensity ratios of the 9632 and 9577 DIBs. In this work, we search for these
DIBs in the ESO VLT/X-shooter archival data and identify the 9632, 9577, 9428
and 9365 Angstrom DIBs in a sample of 25 stars. While the 9428 and 9365
Angstrom DIBs are too noisy to allow any reliable analysis, the 9632 and 9577
Angstrom DIBs are unambiguously detected and, after correcting for telluric
water vapor absorption, their correlation can be used to probe their origin. To
this end, we select a sub-sample of nine hot, O- or B0-type stars of which the
stellar Mg II contamination to the 9632 Angstrom DIB is negligibly small. We
find their equivalent widths, after normalized by reddening to eliminate their
common correlation with the density of interstellar clouds, exhibit a tight,
positive correlation. This supports C60+ as the carrier of the 9632 and 9577
Angstrom DIBs.
