Excitation Temperatures of the Wolf-Rayet Stars

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Abstract
Hydrogenic transitions of C IV are used to derive excitation temperatures for Wolf-Rayet stars of the WC sequence. The line intensities of such transitions in HD 165763, HD 192641, HD 192103 and HD 184738 are derived from measures of equivalent widths on spectra of 10 Å/mm and 20 Å/mm dispersion. These intensities are corrected for continuum values derived by the method of photoelectric spectrophotometry. This technique of temperature determination yields values of temperature unaffected by non-LTE effects in the Wolf-Rayet atmosphere. The mean values obtained are as follows: HD 165763 (WC6) 56 900°±2600°; HD 192641 (WC7) 51 600°±6300°; HD 192103 (WC7) 37 300°±3400°; HD 184738 (WC8) 24000°±4100°K. The intensities of the (4 n ) series of He II are used to derive an excitation temperature of the WN7 star HD 192163, using intensities measured on a single high dispersion Mount Wilson coudé spectrogram. The value derived is 32400°±4200°. A Balmer contribution to the emission of the Pickering series is obvious, though the hydrogen emission present is little. Arguments are presented to show that the (5–9) transition 8236 Å and the (1–15) transition 6406 Å can be utilized on high dispersion spectra for obtaining reliable excitation temperatures of stars of the WN sequence.

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