RADIO OBSERVATIONS OF SN-1987A AT 843 MHZ

We report here the entire history to date of the radio observations of SN 1987A at 843 MHz. These data provide the most comprehensive time sampling of the radio emission from this unique source. Two phases of radio emission from supernova SN 1987A in the Large Magellanic Cloud have been detected with the Molonglo Observatory Synthesis Telescope (MOST) at 843 MHz. At the time of the first observations on 1987 February 25, 2 days after the explosion, the first phase had already begun. The radio flux density peaked within the next 2 days and then decayed monotonically. The flux density dropped below the 3 sigma detectability limit similar to 200 days after the explosion, although the decreasing trend suggests that the emission persisted somewhat longer. In 1990 June, around day 1200, it became apparent that SN 1987A had reappeared at 843 MHz. Later analysis revealed that the onset of this second phase of radio emission occurred considerably earlier. Since then the radio flux density has increased monotonically, and regular observations of SN 1987A with the MOST are continuing.