7 Conclusions

Deep imaging and spectral observations have revealed unknown filamentary and diffuse structures to the north-east of the well known supernova remnant CTB 80. The long, faint filaments in area I are compatible with emission from the cooling zone behind a 90-120 km s^-1 shock propagating into a medium characterized by preshock densities of a few nuclei per cm^-3.

We propose that the optical emission from areas I, Ia, II and IV belongs to a single expanding shell of an unknown remnant. Although emission from shock heated gas is also observed from region III, its relation to the new candidate remnant is less certain. Radio spectral observations are needed to test our suggestions.

Acknowledgements

We would like to thank J. Papamastorakis, J. Ventura and E. V. Palaiologou for their useful comments. We would also like to thank the referee B. Aschenbach whose remarks helped clarify the scope of this paper. Skinakas Observatory is a collaborative project of the University of Crete, the Foundation for Research and Technology-Hellas and the Max-Planck-Institut für Extraterrestrische Physik. This work has been supported by a P.EN.E.D. program of the General Secretariat of Research and Technology of Greece. The Westerbork Synthesis Radio Telescope is operated by ASTRON with financial support from the Netherlands Organization for Scientific Research (NWO). This research has made use of data obtained through the High Energy Astrophysics Science Archive Research Center Online Service, provided by the NASA/Goddard Space Flight Center.