2001A&A...367..635F

We present new Canadian Galactic Plane Survey radio continuum and λ21 cm HI line observations of NRAO 655 (G93.4+1.8), plus radio recombination line observations, and optical H α-line observations. The radio spectrum of NRAO 655 confirms its emission as thermal. From the λ21 cm HI data we find an atomic hydrogen cavity associated with this object at v ≃-71.5km/s. The cavity corresponds in position and size to the brightest radio continuum emission from NRAO 655. The corresponding kinematic distance is 8.8kpc, placing NRAO 655 in the Perseus Arm. NRAO 655's linear size is therefore 70pcx130pc. To confirm the λ21 cm HI velocity we present the first recombination line detection of NRAO 655 (H158 α line, v≃-71km/s), and the first observations of a molecular cloud coinciding with NRAO 655 (at v≃-72km/s). The first optical detection of λ656nm Hα emission line features in NRAO 655 is also presented, and the H α emission line brightness is determined. We suggest that the eastward extension of this strongly asymmetric object originates in a champagne outflow, and we estimate its age. We show that a single early-type star cannot be responsible for the outflow, whereas a group of later-type stars would suffice. A partial HI shell is seen adjacent to the brightest part of NRAO 655; we suggest that it has been formed by dissociation of H₂ in the molecular cloud.