Two supernova remnants of low radio surface brightness discovered in the Canadian Galactic Plane Survey

¹ National Research Council of Canada, Herzberg Institute of Astrophysics, Dominion Radio Astrophysical Observatory, PO Box 248, Penticton, British Columbia, V2A 6K3, Canada e-mail: tom.landecker@nrc.ca
² Department of Physics, University of Alberta, Edmonton, Alberta, T6G 2J1, Canada e-mail: tfoster@phys.ualberta.ca
³ Department of Physics and Astronomy, University of Calgary, Calgary, Alberta, T2N 1N4, Canada e-mail: leahy@iras.ucalgary.ca

Corresponding author: R. Kothes, roland.kothes@nrc.ca

Received: 20 March 2001
Accepted: 2 July 2001

Abstract

Two new supernova remnants (SNRs), G85.4+0.7 and G85.9-0.6, superimposed on the radio source W 80, have been discovered in the radio continuum data from the Canadian Galactic Plane Survey(CGPS). Both SNRs consist of a thin incomplete radio shell surrounding a weak, extended X-ray source. G85.4+0.7 has a thin non-thermal shell of diameter ≈ lying within a thermal shell whose diameter is ≈ . Its radio surface brightness at 1 GHz is Watt m^-2 Hz^-1 sr^-1. It is located within a large Hi bubble, whose systemic velocity, v km s^-1, implies a distance of 3.8 kpc. Two B1 stars detected within this bubble are most likely part of the OB association which formed it. The diameter of the Hi bubble is about 100 pc. The SNR has a diameter of about 30 pc and probably is the result of a type II explosion of an early B star ≈ 6300 years ago. G85.9-0.6 has a radio surface brightness of Watt m^-2 Hz^-1 sr^-1. No Hi features corresponding to the SNR have been detected. This, and the low radio and X-ray brightnesses, suggest expansion in a low-density medium. The SNR may lie in the low-density region between the local and Perseus spiral arms, at a distance of about 5 kpc. Its diameter would then be ~35 pc.