Line formation regions of the UV spectrum of CI Cygni

¹ Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw, Poland e-mail: mikolaj@camk.edu.pl
² Institut d'Astrophysique de Paris – UMR 7095, CNRS/Université Pierre et Marie Curie, 98 bis Boulevard Arago, 75014 Paris, France
³ Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina (CONICET)
⁴ Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, La Plata, Argentina

Received: 7 January 2006
Accepted: 22 August 2006

Abstract

Aims.They are the interpretation of the emission line formation regions in CI Cygni

Methods.They involve the examination of radial velocities and fluxes of ultraviolet emission lines at different epochs, deduced from archival IUE and GRHS/HST spectra.

Results.The line fluxes give electron densities and were in addition used to calculate emission measures, suggesting line formation in regions rather smaller than the binary separation. Examination of the radial velocities led to us to find a systematic redshift of the high ionization resonance lines with respect to the intercombination, and lines. Possible explanations of the redshift and the high resolution GHRS profile are discussed. We favour that involving resonance line absorption by a circum-binary region most probably in an asymmetric wind interaction shell or in a wind from the accretion disk.