IUE observations of high velocity interstellar gas toward stars within the OB association CYG OB1.

Abstract

High-velocity interstellar gas has been detected in IUE spectra of the stars HD 192639, 193514 and 193443 which are members of the OB association Cyg OB1. In all cases where blending between different absorption components is not severe, the authors have derived ion column densities appropriate to the high-velocity gas by fitting theoretical profiles to the observed absorption lines. Previous observations of interstellar gas in the direction of Cyg OB1 are reviewed in an attempt to determine the origin of the high-velocity ultraviolet features. The possibility is discussed that the present observations sample different sections of a large-scale expanding shell around Cyg OB1. Alternatively, the high-velocity gas may be local to the individual stars observed, resulting from the interaction of their energetic stellar winds with the ambient interstellar medium.