Optical Discovery of an Apparent Galactic Supernova Remnant G159.6+7.3
  Deep Halpha images of portions of a faint 3 x 4 degree Halpha shell centered
at l = 159.6 deg, b = 7.3 deg seen on the Virginia Tech Spectral Line Survey
images revealed the presence of several thin emission filaments along its
eastern limb. Low-dispersion optical spectra of two of these filaments covering
the wavelength range of 4500 - 7500 Angstroms show narrow Halpha line emissions
with velocities around -170 +/- 30 km/s. Both the morphology and spectra of
these filaments are consistent with a Balmer dominated shock interpretation and
we propose these optical filaments indicate that the large Halpha emission
shell is a previously unrecognized supernova remnant. ROSAT All Sky Survey
images indicate the possible presence of extremely faint, diffuse emission from
the shell's central region. The shell's location more than seven degrees off
the Galactic plane in a region of relatively low interstellar density may
account for the lack of any reported associated nonthermal radio emissions. The
rare discovery of a Galactic SNR at optical wavelengths suggests that
additional high latitude SNRs may have escaped radio and X-ray detection.
