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A Study of the Planetary Nebulae Abell 30 and Abell 78

Published online by Cambridge University Press:  22 September 2016

M. Cohen ,
H.S. Hudson ,
S.L. O'Dell  and
W.A. Stein
M. Cohen
Affiliation:
University of California, Berkeley
H.S. Hudson
Affiliation:
University of California, San Diego
S.L. O'Dell
Affiliation:
University of California, San Diego
W.A. Stein
Affiliation:
University of Minnesota

Extract

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We have studied the central regions of the planetary nebulae A 30 and A 78 by UBVRI photometry, optical spectroscopy, and near-infrared photometry. The spectra contain high-excitation emission lines and strongly resemble those of Wolt-Rayet stars of the carbon sequence. We infer stellar temperatures > 50,000°K. The observed 3.5-ym flux of each nebula exceeds reasonable extrapolations of both the stellar flux and any possible free-free emission. The colour temperature of this excess between 2.28 and 3.5 /im is ∼ 1000°K. For each nebula, the aperture dependence of the excess emission suggests an extended (y10 arc-sec radius) region centred on the nucleus. Thermal radiation from a distribution of dust that is concentrated near the nuclei seems the most plausible explanation for the excess, but no theory of dust formation or heating seems totally adequate at present. (Paper will appear in the Monthly Notices of the Royal Astronomical Society.)

Type
Session VIII: Planetary Nebulae and Their Influence on the Galaxy
Information
Symposium - International Astronomical Union , Volume 76: Planetary Nebulae , 1978 , pp. 356
Copyright
Copyright © Reidel 1978