2021RNAAS...5...72L

We examine Hubble Space Telescope (HST)/STIS data, complemented with International Ultraviolet Explorer (IUE) data, to delineate interstellar absorption of highly ionized species, C IV, Si IV, and N V, and low ionization species toward four stars in Cygnus. Previous IUE studies indicate two major velocity complexes for C IV and Si IV extending across Cygnus. We see interstellar N V in HST/STIS data for HD 190918 and Cyg X-1. In both stars, the N V is at the velocities of interstellar C IV and Si IV. In HD 190918, the N V is weak, possibly due to enhanced X-ray ionization produced by this binary system. The Cyg X-1 data are of low signal-to-noise, but N V is quite strong with a small b-value, indicating N V arises in a cooler H II region resulting from X-ray Auger ionization by Cyg X-1.