First detection of winds in red giants by microwave continuum techniques

Eight red giants and supergiants have been observed at 4885 MHz (6 cm) with the Very Large Array in an attempt to detect continuum emission. The bright giant Alpha-1 Her (M5 II) was detected at an average flux density of 0.9 + or - 0.13 mJy. Since the likely source of this emission is an ionized, optically thick component of a stellar wind, this detection implies a mass loss rate of 2 x 10 to the -9th solar masses per yr for the ionized gas. The fraction of the outflow in Alpha-1 Her that is ionized (0.002-0.02) seems to be similar to that previously found for Alpha Ori and Alpha Sco A. Alpha Boo (K2 IIIp) and Beta Gem (K0 III) are probable and definite detections, respectively. The derived ionized mass loss rates for these two stars are about 1 x 10 to the -10th solar masses per yr, implying in the case of Alpha Boo that the wind is largely ionized.