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Astron. Astrophys. 323, 183-188 (1997)

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Subtle structures in the wind of P Cygni

F. Vakili , D. Mourard , D. Bonneau , F. Morand and Ph. Stee

Observatoire de la Côte d'Azur, Département Fresnel, CNRS URA 1361, GI2T, F-06460 Saint Vallier de Thiey, France

Received 16 October 1996 / Accepted 18 December 1996


The blue super-giant P Cygni has been observed with the Grand Interféromètre à 2 Télescopes (GI2T). Using high spatial resolution data at low spectral resolution (R=3860) of H [FORMULA] and HeI6678 emission lines we clearly resolve the extended enveloppe of this Luminous Blue Variable on August 1994. The angular diameter of the equivalent uniform disk taken over the total extent of these lines corresponds to [FORMULA] and [FORMULA] mas respectively. We also analysed spectrally-resolved fringes in both lines for 3.4 Å width narrow channels across the emission profiles. Based on robust calibrations from two reference stars [FORMULA] Lyr and [FORMULA] Cep we detect subtle spatial structures throughout P Cyg's wind. First: we find that the maximum extension of P Cyg occurs at -130 km.s-1. This value agrees well with a picture of P Cyg where matter is radially blown outward according to the classical theory of P Cyg line profiles. Secondly: we detect a significant local phase-shift of the fringe signal at -208 km.s-1 which corresponds to an angular separation of 0.8 mas from the continuum source. This is interpreted as a localized blob of moving gas with enhanced brightness whose position is about 4 photospheric radii to the south of P Cyg's underlying star.

Key words: stars: interstellar matter – stars: individual P Cyg – lines: profiles – stars: mass loss – techniques: interferometric

Send offprint requests to: Farrokh Vakili

© European Southern Observatory (ESO) 1997

Online publication: June 5, 1998