AM Herculis - An outburst at 4.9 GHz

The results of radio observations of AM Her with the Very Large Array (VLA) are reported. The quiescent emission first discovered by Chanmugam and Dulk (1982) at 4.9 GHz is confirmed, and upper limits to the flux density at 1.5 GHz and 15 GHz are obtained. The discovery of a remarkable outburst at 4.9 GHz which was essentially 100 percent circularly polarized is also reported. The outburst is probably due to an electron-cyclotron maser which operates near the red-dwarf companion in a region where the magnetic field is about 1000 gauss.