The UV Spectrum of the Binary Star Star 88 Her: Activity Cycles in the circumestellar envelope.

GRANADA, A.; CIDALE, L.; QUIROGA, C.

Praga, Republica Checa

Congreso; Binary Stars as Critical Tools and Tests in Contemporary Astrophysics, International Astronomical Union. Symposium no. 240; 2006

IAU

Since its discovery as a variable star, 88 Her has undergone three long term photometric variation with transitions between Be-shell and normal B phases. From the spectroscopic study of fifteen high resolution spectra obtained by the IUE satellite between 1981 and 1992 we were able to set parameters such as optical depths and location of line forming regions. We also found that the periodic radial velocity variations of UV Fe II lines agree with the binary orbital period of 96.7 days (Harmanec et al, 1974) and that the line absorption depth variations have a cycle of about 1560 days. Our aims are to relate the properties of the circumestellar envelope of 88 Her to the spectroscopic varaibility observed in Fe II and Mg II UV lines, and to understand the mechanisms which cause them, as well as the influence that binarity has on them.