Abstract Details

Name: Gourav Banerjee
Affiliation: Research scholar, CHRIST (Deemed to be University), Bangalore
Conference ID: ASI2021_185
Title : Spectroscopic studies of Galactic Classical Be stars to understand their disc transient nature
Authors and Co-Authors : Gourav Banerjee (CHRIST (Deemed to be University), Bangalore), Blesson Mathew (CHRIST (Deemed to be University), Bangalore), Anjusha Balan (CHRIST (Deemed to be University), Bangalore), K. T. Paul (CHRIST (Deemed to be University), Bangalore), Annapurni Subramaniam (IIA, Bangalore),, Suman Bhattacharyya (CHRIST (Deemed to be University), Bangalore) and R. Anusha (CHRIST (Deemed to be University), Bangalore)
Abstract Type : Poster
Abstract Category : Stars, ISM and Galaxy
Abstract : Classical Be stars (CBe) are massive B-type main-sequence stars with luminosity classes III-V showing emission lines of different elements in their spectra. These emission lines are produced in the gaseous, circumstellar disc that surrounds CBe stars. Many CBe star discs are known to show transient nature within timescales of months to decades. The disc loss and reappearing phases can be identified by studying the Hα line profiles of CBe stars on a regular basis. So we selected 12 bright CBe stars in the Galaxy which are identified to show transient nature. We obtained 236 medium resolution spectra of these stars using the UAGS instrument fitted with the 1.0-m reflecting telescope, situated at the Vainu Bappu Observatory (VBO), Kavalur, India. Continuous monitoring of these 12 stars was carried out since 2017 in the wavelength range 6200 - 6700 Å, particularly centred at Hα. We collated these multi-epoch observations and performed time series analysis to check how Hα line is evolving. In addition to studying the transient behavior of Hα line, we also observed variability in other spectral features such as Fe II 6282, 6516, Si II 6347, 6371 and He I 6678 Å absorption lines while analyzing the multi-epoch spectra. Our results indicate that a possible decline of disc material might have occurred between September 2015 - November 2017 for the star HD 4180. For the star HD 60855, we found that the disc formation has taken place within a timescale of 8 years, from 2008 – 2016. Another 3 stars are identified to be weak emitters with Hα EW < -5 Å. Our study will help in characterizing the evolution of Hα line profiles for our program stars, thus providing a better understanding about the transient nature of CBe stars.