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Astron. Astrophys. 326, 1111-1116 (1997)

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An analysis of emission lines in the spectrum of P Cygni

N. Markova 1 and M. de Groot 2

1 National Astronomical Observatory, P.O.Box 136, BG-4700 Smoljan, Bulgaria
2 Armagh Observatory, College Hill, Armagh BT61 9DG, Northern Ireland

Received 4 September 1996 / Accepted 30 May 1997


Using the coudé spectrograph of the NAO 2m telescope at the Rhodope Mountains, Bulgaria, 9 spectra in the blue and 8 spectra in the red photographic region of P Cygni were obtained during 1990. By averaging the spectra in each set a S/N-ratio of about 45 was achieved. Comparing the lists of identifications published by Beals (1950), de Groot (1969), Ozemre (1978), Stahl et al. (1993), Markova (1994) and Markova & Zamanov (1995), we conclude that the emission spectrum of P Cygni in our days is probably much richer and intensive than 60 years ago. A number of line parameters of the pure emission lines are measured. An estimate of the electron density and temperature in the region of [NII]-lines formation is obtained. Different velocity laws yielding similar density structures are discussed aiming to account for the results obtained on the basis of the [NII] lines. Possible mechanisms for the formation of the permitted pure emission-line spectrum are proposed.

Key words: stars: P Cygni-emission lines - line: formation

Send offprint requests to: N. Markova

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© European Southern Observatory (ESO) 1997

Online publication: April 8, 1998