The well correlated DIBs at $\lambda\lambda$ 6196, 6614 {\AA} and their possible companions

Abstract

Considered here is the interrelation between five diffuse interstellar bands (DIBs): $\lambda\lambda$ 5545, 6113, 6196, 6445 and 6614 \r{A}. Two DIBs ($\lambda$ 6196 and $\lambda$ 6614 \r{A}) have already been known as well correlated with each other; their relation with three other, weaker bands, was investigated for the first time. To accomplish this task high-resolution spectra ($\lambda/\Delta\lambda$ $\approx$ 100,000) with high signal-to-noise ratio (S/N) of 54 hot O -- B stars with reddening 0.12 -- 1.45 mag were used. Analysis of measured equivalent widths has allowed to establish linear dependencies and evaluate linear correlation coefficients as high as 0.968 -- 0.988 between the intensities of these five DIBs. Such a degree of correlation may indicate their common origin. Several spacings in wavenumbers found between these DIBs correspond to the energies of vibrational transitions in some PAHs resulting in IR emissions at $\lambda\lambda$ 16.4, 11.3, 7.7, 6.2 and 3.3 $\mu$m.