An IUE and optical study of interstellar gas towards stars within the Cygnus OB1 and OB3 associations.

Abstract

The interstellar absorption lines formed towards 13 members of the Cyg OB1 and OB3 associations were examined in detail using IUE and optical spectra. Low (0 to +17 km/s), intermediate (-24 km/s), and high (-40 to -70 km/s) velocity components were detected toward most of the stars. It is found that the main component of the highly ionized species at +17 km/s can be identified with a large-scale H II region and the intermediate-velocity component may arise in the Cyg I shell surrounding Cyg OB1. It is suggested that the high-velocity components are formed in a supershell (approximately greater than 70 x 100 pc) surrounding the Cyg OB1 association. It is also found that, from energy considerations, the supershell could easily have been produced by a supernova and/or the combined effects of stellar winds.