  We present the first optical study of the supernova remnant (SNR) G7.7-3.7,
with the aim of determining its evolutionary phase since it has been suggested
to be the remnant of SN 386 AD. We obtained narrow-band images in the filters
H$\alpha$ + [NII], H$\beta$, [OIII], [SII] that revealed faint optical emission
in the southern region of the SNR consisting of two filaments elongated in the
east-west direction aligned with the X-ray emitting region of the remnant. The
filaments were seen in H$\alpha$ + [NII], [OIII] images and marginally in the
[SII] images, with a non-detection in H$\beta$. Long-slit spectroscopy of three
regions along one filament revealed large ratios of [SII] / H$\alpha$ =
(1.6-2.5), consistent with that expected for a shock-heated SNR. The [SII]
doublet ratio observed in two of the regions implies an upper limit for the
electron density of the gas, with estimates falling below 400 cm$^{-3}$ and 600
cm$^{-3}$ in the respective areas. We discuss potential physical mechanisms
that formed the observed optical filaments and we suggest that most likely they
resulted by a collision of the SNR with a dense circumstellar shell lying at
the southern region of the remnant.
