Physics
Scientific paper
Aug 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006iaujd...4e...9l&link_type=abstract
The Ultraviolet Universe: Stars from Birth to Death, 26th meeting of the IAU, Joint Discussion 4, 16-17 August 2006, Prague, Cze
Physics
Scientific paper
Introduction: As it is already known, the spectra of many Oe and Be stars present Discrete Absorption Components (DACs) which, due to their profiles' width as well as the values of the radial velocities, create a complicated profile of the main spectral lines (Bates & Halliwell, 1986). In this poster paper we detect the presence of this phenomenon (DACs or SACs) in the shape of Hα line in the spectra of 120 Be-type stars. Method: In our study we apply the method proposed by Danezis et al. (2003, 2005) on the stellar spectrographs of 120 Be stars, which were taken by Andrillat & Fehrenbach (1982) and Andrillat (1983) (resolution 5,5 and 27 Å) with the telescope of 152 cm in the Observatory of Haute Provence and we examine the variations of the physical parameters, stated below, as a function of the spectral subtype and the luminosity class. Results: We found that in the Be-type stellar atmospheres, there are two regions that can produce the Hα Satellite Absorption Components (SACs or DACs, Danezis et al., 2005). The first one lies in the chromosphere and the second one in the cool extended envelope. With the above method we calculate: a) For the chromospheric absorption components we calculated the optical depth as well as the rotational and radial velocities of the independent regions of matter which produce the main and the satellites components. b) For the emission and absorption components which are created in the cool extended envelope we calculated the FWHM, the optical depth and the radial velocities of the independent regions of matter which produce the main and the satellites components. Discussion: We point out that the new and important aspect of our study is the values' calculation of the above parameters and their variations as a function of spectral subtype and luminosity class, using the DACs or SACs theory. Our results are a successful test of this theory and of Danezis et al. (2003, 2005) proposed method. This study is a part of a Ph. D. Thesis
Antoniou Antonios
Danezis Emanouel
Dimitrijevic Milan S.
Lyratzi Evaggelia
Nikolaidis Dimitris
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