G. J. Nelson

Intense radio outburst from the supermassive star Eta Carinae

On five occasions between 1992 June 29 and 1994 May 3, we have used the Australia Telescope Compact Array (ATCA) to image Eta Carinae at a wavelength of 3 cm and a resolution of 1 arcsec. These observations have revealed remarkable activity. Since 1992 June, the total flux density has increase from 0.8 to 2.2 Jy, and the original single compact source has grown to a complex of sources spread over an area of about 16 sq arcsec. Strong hydrogen recombination-line spectral emission has appeared at the site of the strongest of these new sources. This recombination emission has the largest spectral width ever observed from a star, +/- 250 km/s, and reveals gas with turbulent velocities as great as 250 km/s approaching us at an average velocity of about 200 km/s. We believe that this radio outburst has been caused by a more than threefold increase of ultraviolet luminosity, and consequent ionization of previously neutral gas clouds.

First conclusive evidence for rotational modulation of stellar radio emission

We present what we believe to be the first conclusive evidence for rotational modulation of stellar radio emission, observed on the young and rapidly rotating K1 dwarf star AB Doradus (HD 36705). The radio emission of this star peaked near two stellar longitudes where large starspots have been observed to form preferentially. One of the peaks in radio emission was coincident with the central meridian passage of a large starspot; the starspot associated with the other peak may have been overwhelmed by the visible starspot