Astronomy and Astrophysics – Astronomy
Scientific paper
Oct 1977
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1977mnras.181..233c&link_type=abstract
Monthly Notices of the Royal Astronomical Society, vol. 181, Oct. 1977, p. 233-245.
Astronomy and Astrophysics
Astronomy
44
Absorption Spectra, Astronomical Photometry, Emission Spectra, Planetary Nebulae, Stellar Spectra, Near Infrared Radiation, Optical Emission Spectroscopy, Stellar Temperature, Ubv Spectra, Wolf-Rayet Stars
Scientific paper
The central regions of the planetary nebulae A 30 and A 78 have been studied by UBVRI photometry, optical spectroscopy, and near-infrared photometry. The spectra contain high-excitation emission lines and strongly resemble those of Wolf-Rayet stars of the carbon sequence. Stellar temperatures in excess of 50,000 K are inferred. The observed 3.5-micron flux of each nebula exceeds reasonable extrapolations of both the stellar flux and any possible free-free emission. The color temperature of this excess between 2.28 and 3.5 microns is of the order of 1000 K. For each nebula, the aperture dependence of the excess emission suggests an extended (about 10 arcsec radius) region centered 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.
Cohen Martin
Hudson Hugh S.
Odell S. L.
Stein Wayne A.
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