Long-term variations of the Be star 88 Her.

GRANADA, A.; CIDALE, L.

La Plata, Argentina

Congreso; 48º Reunión Anual de la Asociación Argentina de Astronomía.; 2005

Asociación Argentina de Astronomía.

Since its discovery as a variable star, 88 Her has undergone three photometric long-term variation cycles with transitions between Be-Shell and normal B phases. From the spectroscopic analysis of fifteen high resolution spectra obtained by the IUE satellite, we found that the radial velocities of Fe II lines follow the orbital cycle of the binary system with a period of 86.7 days while their intensities vary with a larger cycle, of about 1560 days. With the aim of contributing to the knowledge of the Be phenomenon, we also determined optical depths and the location of line-forming regions of Fe II. We seek to relate the characteristics of the circumstellar envelope with the observed photometric and spectroscopic variations, and propose a mechanism which could cause them.