G 65.3+5.7
The first CCD mosaics of this supernova remnant
in the optical emission lines of [OII] and [OIII] were obtained from
Skinakas Observatory. The new images reveal several diffuse and filamentary
structures both inside and outside the extent of the remnant. The medium ionization
line of [OIII] 5007 A provides the sharpest view to the system, while the
remnant appears less filamentary in the emission line of [OII]3727 A. There
are significant morphological differences between the two images strongly
suggesting the presence of incomplete shock structures. Long and short scale
variations are observed in several areas of the remnant, the shortest ones
with a length of ~0.6 light-yera. Deep long--slit spectra were taken at several
different positions to study the physical conditions in more detail. All
spectra show that the emission originates from shock heated gas, while the
majority of them is characterized by large [OIII]/Hbeta ratios. The absolute
Ha flux ranges from 0.5--22 x 10^-17 erg/s/cm^2/arcsec^2, while the sulfur
line ratios indicate electron densities below ~200 cm^-3. Estimates of the
shock velocities and the column densities lie in the range of 90-140 km/s.
Finally, the observed variations of the Ha/Hbeta ratios may reflect the presence
of intrinsic absorption affecting the optical spectra.
It is believed that this remnants lies at a distance of ~3000 light-years
and has an ange of ~26000 years.