Astronomy and Astrophysics – Astrophysics
Scientific paper
Mar 1978
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1978apj...220..490m&link_type=abstract
Astrophysical Journal, Part 1, vol. 220, Mar. 1, 1978, p. 490-493, 495-499.
Astronomy and Astrophysics
Astrophysics
53
Abundance, Crab Nebula, Stellar Spectrophotometry, Synchrotron Radiation, Astronomical Models, Electrophotometry, Forbidden Bands, Helium, Hydrogen, Neon, Nitrogen, Oxygen, Sulfur
Scientific paper
Photoelectric spectrophotometry of filaments in the Crab Nebula has been obtained, and intensities for a number of emission lines between 3400 and 7400 A are presented. Temperatures determined from forbidden O III lines range from 11,400 to 16,100 K, while the low-ionization species N II, O II, and S II indicate lower temperatures near 8000 K. Abundance calculations suggest that oxygen, nitrogen, and neon, relative to hydrogen, are within a factor of 10 of what is considered normal. Sulfur appears to be overabundant, but this could be a result of the ionization structure rather than a true abundance effect. Helium lines yield apparent abundances in the range 0.46 to 0.87 relative to hydrogen by number and are consistent with an N(He)/N(H) ratio of approximately unity if allowance is made for neutral helium in the ionized hydrogen regions. There is little doubt that helium is considerably overabundant, and it is likely that the Crab Nebula contains over 1 solar mass of helium.
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