Bipolar Nebulae and Mass Loss from Red Giant Stars

Abstract

Observations of several bipolar nebulae are used to learn something of the nature of mass loss from the probable red-giant progenitors of these nebulae. Phenomena discussed are: probable fluorescent emission bands in the optical and infrared in HD 44179 and GL 2688’s optical molecular emissions; newly discovered very-high velocity knots along the axis of OH 0739–14 which reveal evidence for mass ejections of ±300 km/s from the M9 III star embedded in this nebula; the bipolar structure of three extreme carbon stars, and the evidence for periodic mass ejection in IRC+30219, also at high speed (about 80 km/s); the curious cool TiO-rich region above Parsamian 13 which may represent the very recent shedding of photospheric material from a cool, oxygen-rich giant. Several general key questions about bipolar nebulae, that relate to the process of mass loss from their progenitor stars, are raised.