Polarization within the Interstellar 4430 Å Absorption Band

Abstract

IT was reported by Nandy and Seddon1 recently that the wavelength dependence of interstellar polarization for the star HD 198478 shows a conspicuous band-like feature in a wavelength region coincident with the 4430 A interstellar absorption band. The increase in polarization near the band centre above that of the neighbouring continuum could be in the range 50–100% within the accuracy of the existing data. No satisfactory theoretical interpretation of this phenomenon has yet been given. It seems likely that the new data may hold a clue which could help in the understanding of the nature of diffuse interstellar bands.