Systematic search for galactic supernova remnants

The positions of all known radio supernova remnants have been searched for optical emission nebulosity. New optical supernova remnants identified during this program are G130.7 + 3.1= 3C 58, G206.9 + 2.3= PKS 0646 + 06, G296.1--0.7, G326.3--1.8= MSH 15--56, and G327.6 + 14.5= PKS 1459--41= Lupus SN 1006. New observations suggest that G74.8 + 0.6, G78.1 + 1.8, G284.2--1.8, and G339.2--0.4 are unlikely to be supernova remnants.Of 124 probable galactic SNRs listed in Table 1 all but one (G343.2--5.6) are known to be radio sources. A total of 29 SNRs have now been observed optically. In the anticenter direction (900 <l<2700) 16 of 22 known sources (73%) are identified, whereas only 13 out of 102 (13%) of the sources in the galactic center direction (2700<l<900) are visible optically.Between 5% and 10% of the supernova remnants near the Sun are presently still recognizable as being of the Crab-like variety. The average time interval between the formation of galactic pulsars is estimated to be approx.150 years.It is speculated that the ''Lupus Loop'' might have been produced by relativistic plasma ejected by the supernova of 1006 with a velocity approx.0.2c