Abstract
view Abstract Citations (35) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Study of Emission-Line Intensities in Some Bright Northern Wolf-Rayet Stars. Aller, Lawrence H. Abstract From a study of emission-line intensities in a number of bright Woif-Rayet stars excitation tempera- tures of their atmospheric envelopes are estimated. These temperatures turn out to be very high and de- pend upon the ionization potential of the ion employed-in the sense that the higher the ionization po- tential, the higher the resultant temperature. The emission lines in the Woif-Rayet stars probably do not arise from the primary mechanism, i.e., photoionization and subsequent recapture of electrons, but rather from the absorption of high-frequency radiation emerging from the lower layers. On the basis of certain plausible assumptions an attempt is made to find the chemical composition of the atmospheric layers. In the carbon stars helium is estimated to be about fifty times as abundant as oxygen and fifteen times as abundant as carbon, while in the nitrogen stars helium appears to be about twenty times as abundant as nitrogen and three hundred times as abundant as carbon. The estimate of the abundance of helium with respect to other gases is very uncertain. The nuclei of BD+30°3639 and NGC 40 seem to be typical carbon stars. The nucleus of NGC 6543, which contains both nitrogen and carbon, seems to show a rela- tively small range of ionization. The chemical composition of the Woif-Rayet stars seems to be more closely related to that of the super- novae than to the envelopes of ordinary novae, which appear to have roughly the same composition, on the average, as the planetary nebulae and normal stars. The electron densities in the radiating layers of a Woif-Rayet star appear to be of the order of 1Oh1~~1O12 electrons/cm3, much greater than the electron densities in the envelope of a nova. The background spec- trum of the star is sufficiently intense to blot out any forbidden lines that may appear Publication: The Astrophysical Journal Pub Date: March 1943 DOI: 10.1086/144508 Bibcode: 1943ApJ....97..135A full text sources ADS | data products SIMBAD (1)
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