Radio Monitoring of Supernova 2001ig: The First Year

Supernova 2001ig in NGC 7424 has been observed with the Australia Telescope Compact Array at ∼2 week intervals since its discovery, making this the best-studied Type IIb radio supernova since SN 1993J.We present radio light curves for frequencies from 1.4 to 20 GHz, and preliminary attempts to model the observed behavior. Since peaking in radio luminosity at 8.6 and 4.8 GHz some 1–2 months after the explosion, SN 2001ig has on at least two occasions deviated significantly from a smooth decline, indicative of interaction with a dense circumstellar medium and possibly of periodic progenitor mass-loss.