SIMBAD references

We confirm the reality of a reversal of the sign of the Faraday rotation measure in the Galactic plane in Cygnus (Lazio et al. 1990), possibly associated with the Cygnus OB1 association. The rotation measure changes by several hundred rad/m2 over an angular scale of 2°-5°. We show that a simple model of an expanding plasma shell with an enhanced density and magnetic field can account for the magnitude and angular scale of this feature. This model is consistent with observations of Hα emission as well as other observations in this part of sky. We suggest that this structure is physically associated with a superbubble produced by the Cygnus OB1 association.