THE CLUMPY GALAXY MARKARIAN 297 AND ITS SUPERNOVA ACTIVITY

I present radio observations of the clumpy irregular galaxy Mrk 297 (= NGC 6052) made with the VLA at 20, 6, 3.6, and 2 cm from 1980 January to 1992 April, which show that the variable, compact source (Mrk 297A ) is a single supernova with the highest peak radio luminosity known f or a supernova. Twenty-one VLA flux-density measurements at four wavel engths of the compact source, obtained over the past 12 yr, yield a sa tisfactory fit to Chevalier's model for supernova light curves. Shorte r period fluctuations in the observations are significant and are cons istent with refractive interstellar scintillation. The supernova rate for the entire galaxy can be estimated from a global formula (Condon & Yin 1990) which uniquely relates total nonthermal radio emission to s upernova rate. The resulting supernova rate estimated for the entire g alaxy Mrk 297 is high (0.3 yr-1). However, most individual Type II rad io supernovae are too weak to be detected at the distance of Mrk 297.