Odd Radio Circles as supernovae remnants in the intragroup medium
  A measurable fraction ($\sim8$ per cent) of recently discovered arcmin-size
circular diffuse radio sources termed as Odd Radio Circles or ORCs can be
supernovae remnants in the intragroup medium, within the local group and its
immediate neighbour groups of galaxies. This estimate is based on the optical
detection rate of the intragroup supernovae events in the nearby ($z \sim
0.1-0.2$) galaxy groups. A rate of about 5400 intragroup supernovae per million
year is expected within the local and its immediate neighbour groups of
galaxies. For a radio detectability period of about $10^{4}$ years, on average
1.3 intragroup medium supernovae remnants per 1000 square degree are expected
to be detected in the radio surveys with a sensitivity that led to discovery of
ORCs. The angular size, surface brightness and radio flux of the supernova
remnants up to a distance of $\sim3$ Mpc in the intragroup medium can be
expected to be similar to the five known ORCs. The intragroup supernovae
remnants are not residing in the dense and cold interstellar medium of the
galaxies but evolving in low density ($10^{-4}-10^{-5}$ cm$^{-3}$) warm medium
($10^{5}-10^{6}$ K) in galactic halos or beyond, and may find their progenitors
in the diffuse stellar light associated with various tidal streamers
surrounding the Milky-Way and other nearby galaxies.
