INTENSE RADIO OUTBURST FROM THE SUPERMASSIVE STAR ETA-CARINAE

On five occasions between 1999 June 29 and 1994 May 3, we have used th e Australia Telescope Compact Array to image eta Carinae at a waveleng th of 3 cm and a resolution of 1''. These observations have revealed r emarkable activity. Since 1992 June, the total flux density has increa se from 0.8 to 2.2 Jy, and the original single compact source has grow n to a complex of sources spread over an area of about 16 arcsec(2) (F ig. 1). Strong hydrogen recombination-line spectral emission has appea red at the site of the strongest of these new sources. This recombinat ion emission has the largest spectral width ever observed from a star, +/-250 km s(-1) and reveals gas with turbulent velocities as great as 250 km s(-1) approaching us at an average velocity of about 200 km s- (1). We believe that this radio outburst has been caused by a more tha n threefold increase of ultraviolet luminosity, and consequent ionizat ion of previously neutral gas clouds.