Abstract
Low spectral resolution observations (∼ 6 A) were obtained with the International Ultraviolet Explorer (IUE) during its eclipse phase. Additional data obtained by other IUE groups have been included in our eclipse observations, enabling us to examine the UV spectral properties of this system over nearly an entire orbit that spans early 1979 through mid-1981. Data obtained over this time interval suggest an overall decline in UV emission consistent with the decline of optical emission following the outburst of 1975, where CI Cyg attained an increase of ∼ 3 magnitudes in the visual. The short wavelength spectrum λλ1200–2000 A is characterized by numerous intense high excitation emission lines that become more prominent out of eclipse. The LWR wavelength range λλ2000–3200 A exhibits a few more additional lines of O III, Mg II and He II that are superimposed on continuum that rises gradually with increasing wavelength. Additionally, OH emission bands are identified at λλ3064, 2875 A (cf. Diecke and Crosswhite 1962). Collaborative ground-based observations of CI Cyg with W. Blair of McGraw Hill Observatory suggest the presence of the Balmer continuum jump at λ3646 A, and enables us to ascribe the UV continuum observed with IUE to mainly Balmer free-bound recombination emission.
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