G55.0- A HIGHLY EVOLVED SUPERNOVA REMNANT(0.3 )

In order to determine the nature of an object identified as a potentia l supernova remnant (SNR) in a 327 MHz survey of the Galactic plane, c ontinuum observations have been taken at 1420 MHz with resolution iden tical to that of the survey. Additionally, atomic hydrogen (H I) spect ral line data have been taken in order to determine the distance to th e object. Multifrequency analysis shows that a shell feature in the so uthern part of this object is nonthermal and confirms earlier studies that identified the northern portion as an H II region. The nonthermal nature of the shell and the absence of infrared flux density confirms the speculation of Taylor, Wallace, & Goss that this object, G55.0 +/ - 0.3, is an SNR. From analysis of H I data, the SNR's estimated kinem atic distance is 14 kpc, yielding a radius of approximately 70 pc, mak ing it one of the largest known SNRs. The age estimate on the order of 1 million years exceeds the conventional limits on observable SNR lif etimes in the literature by a factor of 5, implying that the radiative lifetimes of SNRs could be much longer than previously suggested. The re is also evidence that the remnant may be associated with the nearby pulsar J1932 +/- 2020. This proposed SNR/pulsar association is older than any previously documented by an order of magnitude. If valid, it suggests that searches for associations should not be restricted to th e regions around young pulsars.