Variation at Hα Emission Line in a Unique Be Star γ Cassiopeiae

Abstract

The well known Be star γ Cassiopeiae (γ Cas) is being observed spectroscopically and photometrically for the last nearly one and half century. This star is a prototypical "classical" Be star which resulted in many new discoveries in Be phenomena. This was first B star with Balmer line emission, thus opening a new class of B stars called Be stars. Due to its unique and fascinating nature we plan to include this object in our regular observing program. In the present communication we report the Hα observations of this object. The spectrophotometric spectral scans of this star covering the Hα region in the wavelength range 6100 - 6900 Å are presented to explore the variations of Hα emission strength and shape of the line. The star displayed unusual behaviour at Hα emission line during the period of observations. Reversal of asymmetry from V>R to V<R along with the transformation from double-peaked emission to a single -peaked emission at Hα emission line has been explored on time-scales of about weeks. High time resolution observations show possible ultra-rapid variations in Hα emission strength and shape on time-scale of minutes to seconds.