Book contents
- Frontmatter
- Contents
- Preface
- Conference Photograph
- Conference Participants
- Part one Stellar Evolution and Wind Theory
- Part two Wolf-Rayet Ring Nebulae
- Part three Supernovae
- Part four Asymptotic Giant Branch stars
- Part five Planetary Nebulae
- Morphology and kinematics of PNe
- FLIERs in elliptical Planetary Nebulae
- Circumstellar dust in PN and PPN
- H-poor ejecta in A30 and A78
- The neutral envelopes of PNe
- Magnetic shaping of Planetary Nebulae
- Aspherical two-wind configurations
- Part six Novae and Symbiotic Stars
- Poster Papers
- Author Index
- Object Index
H-poor ejecta in A30 and A78
from Part five - Planetary Nebulae
Published online by Cambridge University Press: 07 September 2010
- Frontmatter
- Contents
- Preface
- Conference Photograph
- Conference Participants
- Part one Stellar Evolution and Wind Theory
- Part two Wolf-Rayet Ring Nebulae
- Part three Supernovae
- Part four Asymptotic Giant Branch stars
- Part five Planetary Nebulae
- Morphology and kinematics of PNe
- FLIERs in elliptical Planetary Nebulae
- Circumstellar dust in PN and PPN
- H-poor ejecta in A30 and A78
- The neutral envelopes of PNe
- Magnetic shaping of Planetary Nebulae
- Aspherical two-wind configurations
- Part six Novae and Symbiotic Stars
- Poster Papers
- Author Index
- Object Index
Summary
Introduction
Abell 30 and Abell 78 are the best-known members of a small but important class of planetary nebulae (PNe) which are characterized by H-poor, dusty ejecta. Other members of this group include Abell 58 (V605 Aql), IRAS 18333-2357 (in the globular cluster M22) and IRAS 15154-5258. In these objects the H-poor material is surrounded by an outer envelope of normal composition (except for IRAS 18333-2357, where the ram pressure of the ISM would have stripped off the outer envelope: Borkowski et al. 1993a). Clearly, a secondary ejection of highly processed material has occurred after the loss of the hydrogen envelope of the AGB progenitor. A detailed interpretation was put forward by Iben et al. (1983), who proposed a final helium shell flash after nearly all of the H-rich envelope had been expelled.
The H-poor PNe are important because the composition of the ejecta opens a window upon the final phase of AGB nucleosynthesis and dredge-up, and also because the high dust to gas ratio lets us study the physics of dusty plasmas (e.g., gas heating by photoelectrons from grains: Borkowski & Harrington 1991). Here, however, we wish to point out that at least two of these objects also provide an exceptional opportunity to study mass-loaded flows. Mass-loading occurs when a tenuous, fast wind, as it streams around dense, slow-moving knots, entrains and mixes with bits of the dense material.
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- Circumstellar Media in Late Stages of Stellar Evolution , pp. 300 - 303Publisher: Cambridge University PressPrint publication year: 1994