2003A&A...398..153M

Flux calibrated images of the field around the known supernova remnant G 73.9+0.9 in the Hα+[NII], [SII], [OII], and [OIII] emission lines are presented. The low ionization images are characterized by diffuse emission both within and outside the extent of the remnant. The flux calibrated images revealed a few small scale structures in the east areas of G 73.9+0.9. The long-slit spectra identify the emission from one of them as emission from shock heated gas. This patchy structure is ∼3' long and emits Hα flux at a level of ∼33x10^–17erg/s/cm²/arcsec². The bright diffuse arc-like structure in the center of the field seems to be associated to G 73.9+0.9 given its spectral signature and positional relation with the non-thermal radio emission. A ∼8' long filamentary structure with an absolute Hα flux of ∼9x10^–17erg/s/cm²/arcsec² is detected in the [OIII] emission line to the south of G 73.9+0.9 but is probably unrelated. The deep long-slit spectra suggest complete recombination zones, shock velocities below 90km/s, low electron densities (<50cm^–3) and non-negligible magnetic field strengths.