Abstract Details

Name: Shruthi S Bhat
Affiliation: Christ University
Conference ID: ASI2017_431
Title : Near-Infrared Spectroscopic Study of Classical Be Stars
Authors and Co-Authors : Shruthi S Bhat (Christ University, Bangalore), Paul K T (Christ University, Bangalore), Annapurni Subramaniam (Indian Institute of Astrophysics, Bangalore), Blesson Mathew (Tata Institute of Fundamental Research, Mumbai)
Abstract Type : Poster
Abstract Category : Stars,ISM and the Galaxy
Abstract : We present the preliminary results from the Near-Infrared (NIR) spectroscopic study of a sample of 23 Classical Be stars observed using TIFR Near Infrared Spectrometer and Imager (TIRSPEC) mounted on 2m Himalayan Chandra Telescope (HCT), Hanle. The observations were conducted during the period 2015 - 2016. All the stars were observed in 1 - 2.3 micron spectral region, which includes Y, J, H and K bands, at R ~ 1200. NIR spectroscopy provides a powerful tool to understand the changes in the inner circumstellar disk of Be stars since HI emission lines in this spectral window originates in a region close to the star; whereas those in optical, like Hα, are formed at a distance of 4 - 10 stellar radii. The most intense emission lines in the NIR wavelength region are due to HI lines belonging to Paschen and Brackett series, with the prominent ones being Paβ, Paγ and Brγ. Due to the location of the telescope (HCT), most of the Be stars included in the study belong to northern sky, which complements well with the previous studies of southern Be stars. An important issue which is not addressed often is the role of opacity effects in the emission strength of NIR HI lines. This is particularly interesting since mass-loss from the central star gets accumulated in the inner orbit, from where it is spread out uniformly through viscous decretion mechanism. From the analysis of flux ratio of emission lines we calculate the opacity effects of prominent HI emission lines. By means of free-free emission model, which accounts for infrared excess in Be stars, we estimate the electron density of the line forming region.