A deep echelle survey and new analysis of diffuse interstellar bands

Abstract

We report a deep survey of diffuse interstellar bands (DIBs) between 3906 Å and 6812 Åunder consistent observing conditions toward three very reddened and five unreddened stars. BD+63° 1964's line-of-sight was shown to present exceptional DIB enhancement in number as well as in strength. The early spectral type of the star and the use of spectra of an unreddened comparison star of the same spectral type allowed to limit stellar line residuals. Using careful reduction and analysis methods we discovered 60 new DIBs which are confirmed in the reddened targets HD 183143 and BD+40° 4220. We detected 25 possible DIBs which still await further confirmation, but we did not detect or confirm 28 previously reported DIBs. The present survey with 226 confirmed DIBs, measured in three targets allows a detailed and homogeneous statistical analysis on the distribution of DIB widths and intensities.