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Astron. Astrophys. 327, 337-341 (1997)

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5. Conclusions

We find that the band width and band profiles of two DIBs previously assigned to C60[FORMULA] are similar and that the bands weaken in dense cloud environments in a similar manner. We also find that the band positions are consistent with a similar shift for both lines, amounting to about +6.5 Å between gas-phase DIBs and the absorptions measured in the laboratory. These results argue in favor of the C60[FORMULA] assignment.

However, we find that the ratio of [FORMULA] 9632 to [FORMULA] 9577 is less than previously reported and significantly less than the relative peak intensity of the corresponding laboratory positions of C60[FORMULA]. Both DIBs are also weaker in the diffuse medium than previously reported. Only if gas-phase C60[FORMULA] has band intensity ratios much different from those measured in the neon matrix is there a chance that these DIBs are due to C60[FORMULA].

We do not find the corresponding vibrational excited transitions near 9400 Å which, however, were expected to be present at only 1-2 sigma above our detection limit.

The diffuse interstellar bands have still not been identified with certainty. At present, C60[FORMULA] merely joins a long queue of promising molecules proposed as carriers of the over 200 absorptions in the visible and near-infrared spectra of reddened stars. However, the case for C60[FORMULA] is better than for many other candidates and now rests in the court of laboratory spectroscopists.

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© European Southern Observatory (ESO) 1997

Online publication: April 8, 1998