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Session 38 - Disks and Bipolar Outflows from Hot Stars.
Display session, Tuesday, June 11
We report on the results obtained from an analysis of IUE high and low resolution 1200-3200 Å\ spectroscopy and FOS 1300-1600 Å\ spectropolarimetry of the eclipsing interacting binary V356 Sgr. This binary system consists of an early B star that exhibits a B2II spectrum accreting matter from a Roche-lobe filling A2II star. The orbital period is 8.896 days. Ultraviolet spectroscopic observations with IUE, spanning 15 years, have shown that the system displays strong, broad emission lines, including N V and Si IV, during the total eclipse (C IV is not seen because the circumstellar matter is composed of CNO processed material) but a relatively normal B-type spectrum, without emission lines, outside of eclipse. The FOS observations were obtained in outside of eclipse in October 1993. The new analysis of the IUE and HST data argue that the B2II spectrum is not a photospheric spectrum but, rather, arises in a compact, optically thick ``disk'' with substantial vertical extent. This ``disk'' is also asymmetrically distributed around the accreting star. The behavior of the emission lines through total eclipse imply that these emissions arise in a region well removed from the immediate vicinity of the two stars, and are associated with a bipolar flow of matter from the accreting source. A scattered light continuum, consistent with the FOS spectropolarimetry results, is also seen in the IUE data. This continuum exhibits some occultation during total eclipse and must originate closer to the stellar components than the emission lines. A model is presented for the origin and structure of the circumstellar matter in this binary.
Program listing for Tuesday