The optical interstellar spectra of the Wolf-Rayet stars HD 192163 and 191765

The principal atomic line and unidentified diffuse band absorptions have been studied in the spectra of two WN6 stars, HD 192163 and 191765. Equivalent widths for all features are found to be consistent with the reddening, in contrast to the anomalously very strong lambda 2200 ultraviolet feature found in HD 192163. The earlier report of an anomalously strong lambda 6283 diffuse band in this star is not confirmed. The atomic sodium and ionized calcium lines for HD 192163 show evidence for a violet-displaced component which is attributed to interstellar gas swept up by the expanding circumstellar nebula NGC 6888. (author)