2004A&A...424..583B

Further deep, narrow-band images in the light of [O III] 5007Å have been added to the previous mosaic of the faint galactic supernova remnant G 65.3+5.7. Additionally, long-slit spatially resolved [O III] 5007Å line profiles have been obtained at sample positions using the Manchester Echelle Spectrometer at the San Pedro Martir observatory. The remnant is shown to be predominantly bi-lobal with an EW axis. However, a faint additional northern lobe has now been revealed. The splitting of the profiles along the slit lengths, when extrapolated to the centre of the remnant, although uncertain, suggests that the expansion velocity of this remnant is between 124 and 187km/s i.e. much lower than the 400km/s previously predicted for the forward shock velocity from the X-ray emission. An expansion proper motion measurement of 2.1±0.4arcsec in 48-years for the remnant's filamentary edge in the light of Hα + [N II] 6548 and 6584Å has also been made. This is combined with an expansion velocity of ≃155km/s, a distance of ≃800pc is derived. Several possibilities are considered for the large difference in the expansion velocity measured here and the 400km/s shock velocity required to generate the X-ray emission. It is also suggested that the morphology of the remnant may be created by a tilt in the galactic magnetic field in this vicinity.