THE HE-3 ABUNDANCE IN PLANETARY-NEBULAE

We report measurements of the abundance of He-3 for a sample of six Ga lactic planetary nebulae: IC 289, NGC 3242, NGC 6543, NGC 6720, NGC 70 09, and NGC 7662. Based on observations of the 8.665 GHz hyperfine tra nsition of He-3(+), we derive He-3/H abundances ranging from similar t o-0.1 to 1.0 x 10(-3) by number. These abundances are more than an ord er of magnitude larger than those found in any H II region, the local interstellar medium, or the proto-solar system. If planetary nebulae a re surrounded by large, low-density, ionized halos, modeling suggests that these abundances will decrease by a factor of about 2. Our source sample is highly biased in that we selected objects on the basis of s everal criteria that maximized the likelihood of He-3 detections. The abundances are nonetheless consistent with the idea that He-3 is produ ced in significant quantities by stars of 1-2 M.. We conclude that the re is some stellar production of He-3.