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Astron. Astrophys. 317, L28-L31 (1997)

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Letter to the Editor

Diffuse Interstellar Bands towards BD+ 63° 1964 *

A new reference target

P. Ehrenfreund 1, 2, J. Cami 1, E. Dartois 2 and B.H. Foing 3, 2

1 Leiden Observatory, P.O. Box 9513, 2300 RA Leiden, The Netherlands
2 Institut Astrophysique Spatiale, CNRS, Bat 121, Campus d'Orsay, France
3 Solar System Division, ESA Space Science Department, ESTEC/SO, 2200 AG Noordwijk, The Netherlands

Received 5 November 1996 / Accepted 3 December 1996


We report the discovery of a remarkable target concerning the Diffuse Interstellar Bands (DIBs), namely BD+ [FORMULA] 1964. The unusual high DIB strengths in this object allow to confirm DIBs that were so far denoted only as "probable", because of their intrinsic weakness in most lines-of-sight. Due to specific line-of-sight conditions, the high reddening and the early spectral type of the star, this object is proposed as a new reference star for DIB measurements. We compared the spectrum of BD+ [FORMULA] 1964 to the spectrum of the well studied star HD183143. Line-of-sight parameters such a far UV extinction and Ca I abundance indicate a denser environment towards BD+ [FORMULA] 1964, which can shield molecules efficiently from far UV radiation above 6 eV. The relative enhancement of narrow DIBs in BD+ [FORMULA] 1964 versus HD183143 is then discussed in the context of neutral fullerene compounds or large PAHs. The relative weakening of broad DIBs indicate carriers with higher photo-ionization potential and different recombination properties.

Key words: ISM: molecules - ISM: dust,extinction - Stars: individual: BD+63O 1964, HD183143; Line: profiles

* Based on observations at Observatoire Haute Provence with the spectrograph ELODIE.

Send offprint requests to: P. Ehrenfreund

© European Southern Observatory (ESO) 1997

Online publication: July 8, 1998