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A compact planetary nebula around the hot white dwarf EGB 6/PG 0950 + 139The remarkable central star (0950 + 139), a very hot DA/DAO white dwarf, of the planetary nebula EGB 6 is described. Follow-up observations relevant to the analyses of both the nebula and the stellar photosphere are presented. Three kinds of scenarios are discussed to account for the existence of this peculiar nebula, but none appears very promising. The first consideration is that the nebula was ejected from the white dwarf as a discret event. This hypothesis is heavily constrained by the nebular size, density, and expansion rate; by the low luminosity and radius of the star; and by the absence of evidence for variation in density-sensitive forbidden lines from 1978 to 1987. No plausible mechanism can cause the observed amount of mass to be lost directly from a white dwarf in a steady or sporadic wind, at outflow velocities orders of magnitude below the escape velocity. Final consideration is given to the possibility that the gas is lost from a close companion star, but there is no evidence that this is a close binary system.
Document ID
19900025996
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Liebert, James (Steward Observatory, Tucson, AZ ; Mount Wilson and Las Campanas Observatories, Pasadena CA, United States)
Green, Richard (Kitt Peak National Observatory Tucson, AZ, United States)
Bond, Howard E. (Space Telescope Science Institute Baltimore, MD, United States)
Holberg, J. B. (Mount Wilson and Las Campanas Observatories, Pasadena, CA; Arizona, University Tucson, United States)
Wesemael, F. (Mount Wilson and Las Campanas Observatories, Pasadena, CA; Montreal, Universite Montreal, Canada)
Date Acquired
August 14, 2013
Publication Date
November 1, 1989
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 346
ISSN: 0004-637X
Subject Category
ASTROPHYSICS
Funding Number(s)
CONTRACT_GRANT: NAG5-434
CONTRACT_GRANT: NSF AST-88-40482
Distribution Limits
Public
Copyright
Other