Very high resolution profiles of 6196 Å and 6614 Å diffuse interstellar bands

Abstract

We present a careful analysis of very high resolution (R = 220000) profiles of two well correlated diffuse interstellar bands (DIBs): 6196 and 6614 A observed along 7 lines of sight free of the Doppler splitting in interstellar atomic lines. The high signal-to-noise ratio (S/N) of the spectra (∼600-1000) allows us to draw definite conclusion that the ratio of equivalent widths of the two DIBs is not always exactly the same, i.e. they do not seem to originate at the same carrier. The DIB profiles vary from object to object but the variations are different for every DIB. The width of 6196 DIB may change by up to 1.5 times lowest value while that of 6614 remains almost constant. The broadening of 6196 is not caused by the Doppler splitting, absent in atomic interstellar lines. Possibly this fact reflects a strong dependence of the carrier excitation pattern on small variations of physical parameters. The variations of substructure strength ratios inside the 6614 DIB profile, evident in our spectra, are apparently caused by a mechanism different from that which broadens DIB 6196.