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Description
Be stars are fast rotating early-type emission line stars. It is generally assumed that observed emission is generated in a rotating disk- like envelope, as supported by the observed correlation between the stellar projected rotational velocity v sin i and the width of the emission lines. Then, high resolution spectroscopic observations of Balmer lines profiles play an important role in putting constrains on Be stars modeling. We present Balmer lines spectroscopy for a sample of 48 Be stars. For most of them, H{alpha} and H{beta} have been observed more than two times, in a total period spanning almost two years between 2008 and 2009. Spectral synthesis of the H{alpha} profile has been performed following two steps: photospheric contribution has been computed by using Kurucz's code ATLAS9 and SYNTHE, and disk emission have been derived by the approach of Hummel & Vrancken (1995A&A...302..751H). For 26 out of 48 stars, a modeling of the total H{alpha} emission, i.e. photospheric absorption plus disk net emission, has been attempted. By this modeling we derived an estimation of the disk radius, as well as the inclination angle between rotational axis and line of sight and the base density at the stellar equator. We also discussed, for the stars observed more than once, the variability of H{alpha} and H{beta} for what concerns both the equivalent width and the spectral profile. We found 16 stars with variable equivalent width and 7 stars with clear sign of profile variations. For all the stars of our sample we derive all the fundamental astrophysical quantities, such as: effective temperature, gravity, and projected rotational velocity. We found 13 stars which equivalent width is variable with a confidence level greater than 80% and 7 object for which spectral profiles show change with time. According to the classification scheme commonly used in literature, we classified 16 stars as belonging to class 1, 13 to class 2, 11 are shell stars, 6 objects do not show net emission, and 2 stars display transition from class 1 and 2. For the class 1 stars, we confirm the correlation between vsini and peak separation. concerning the geometry of the disk, we derived the inclination angle between rotational axis and line of sight, the base density at the stellar equator, and the radius. The maximum concentration of stars occur for disk dimensions ranging in the interval of 6 to 8 stellar radii and for inclination angles going from 23{deg} to 35{deg}.
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