| Abstract: | A classical Be (Be) star is a massive B-type main sequence star surrounded by a geometrically thin, equatorial, gaseous, decretion disc orbiting in Keplerian rotation. Spectra of Be stars show emission lines of different elements, studying which we can gain insights about their circumstellar discs and the central star itself. Mathew et al. (2011) performed a slitless spectroscopic survey to study the spectral features of 150 Be stars in open clusters. Their study motivated in performing further spectroscopic surveys of Galactic Be stars in different environments. My PhD research focused on the study of field Be stars in the Galaxy using optical spectroscopy, obtaining data from HCT facility, Ladakh and multi-epoch spectra from the 1-m CZT facility, VBO, IIA.
We produced an atlas of all major emission lines found in a large sample of 115 Galactic field Be stars (Banerjee et al. 2021) using the HCT facility. Then, we (Banerjee et al. 2024) further explored these stars to better understand their disc properties. Our evaluation of the electron density in Be star discs using Balmer decrement values indicate that their discs are generally optically thick in nature with electron density (n_e) in their circumstellar envelopes (CEs) being in excess of 10^13 cm^-3 for around 65% of the stars. Another study of ours (Banerjee et al. 2022) focused in understanding the disc transient nature of Be stars through continuous monitoring of their Hα line profile variations for 5 consecutive years (2015 -- 2019) using the 1-m facility at Kavalur. Our results suggested that 4 among the 9 sample stars are possibly undergoing disc-loss episodes and one other star might be passing through disc formation phase, rest 4 stars may be hosting a stable disc presently. These results further motivated to start two new projects, which I am currently leading as PI from VBO, Kavalur as a PDF at IIA. |
