Diffuse interstellar bands towards BD+63^o 1964: A new reference target

We report the discovery of a remarkable target concerning the Diffuse Interstellar Bands (DIBs), namely BD+63^o 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+63^o 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+63^o 1964, which can shield molecules efficiently from far UV radiation above 6 eV. The relative enhancement of narrow DIBs in BD+63^o 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.