SAKURAIS OBJECT - THE IONIZED NEBULA AT RADIO WAVELENGTHS

Sakurai's object (V4334 Sgr) is a planetary nebula nucleus which is un dergoing its final helium shell flash. This is the first of these rare and important events to be observable with non-optical instruments. W e report the first radio detection, using a short (2-h) observation wi th the Very Large Array (VLA) at 4.86 GHz. The radio emission structur e is coincident with the 34-arcsec diameter planetary nebula seen in o ptical emission lines. We find a statistical distance similar to 3.8 /- 0.6 kpc, with a range of 1.9 < D < 5.3 kpc, depending on the planet ary nebula (PN) mass. While we have no direct evidence for a new (post -flash) stellar wind, we estimate an upper limit to the mass-loss rate due to any such wind of 1.7 x 10(-7) M-. yr-l. The number of emitting knots in the radio-visible nebula indicates an electron density of si milar to 2 x 10(8) m(-3) in those knots, and a total emitting ionized mass of similar to 0.15 M-., at an assumed distance of 3.8 kpc. The ra dio flux density indicates an H beta flux of similar to 6 x 10(-16) W m(-2), suggesting an extinction E(B - V) similar to 1.15, comparable w ith reddening estimates in the direction of V4334 Sgr.