Abstract:
U Sge (HD 181182) belongs to the group of short period Algol-type binaries with a period of 3.38 days. One hundred and eleven high-resolution spectra of U Sge, which are known to exhibit Hα emission, were obtained at (TÜBİTAK) National Observatory in Turkey. The emission and absorption structures of the system have been analysed. The astrophysical parameters of the system have been obtained by means of analysing the spectral and photometric data. Accordingly, the primary component is a B7-8 spectral type main-sequence star, while the secondary component is a G2 spectral type giant. The cool secondary component has filled its Roche lobe and is transferring material through the L1 point onto the hot primary component. The effects of both components and the transferring material were detected in the Hα lines. In order to determine these effects, the SHELLSPEC code, which uses an LTE approximation, has been used. The circumstellar structure around U Sge is due to a very low density disk, transferring material, a hot spot where the transferring material from the secondary impacts onto the primary and the magnetic activity from secondary itself. Moreover, all of these effects on the system are highly variable in just a few orbital cycles.
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