Abstract
Be stars have a very rapid rotation that leads, along with other mechanisms, to the generation of circumstellar decretion disks. Spectroscopic analysis of their Hydrogen emission lines in the infrared can be useful to understand the disk evolution. This is possible through characterizing the dependency with wavelenght of physical parameters of the lines, such as integrated flux and full width at half maximum. In this work, we obtained integrated fluxes for Humphreys, Pfund and Brackett spectral lines of a sample of 3 Be stars: γ Cas, φ Per and 28 Tau. With these data, we analized changes in optical depth and density of the disks. We found that the circumstellar disks of these stars are optically thin, based on a flux ratio diagram and from a qualitative description of the morphology found in the infrared spectra. We studied also the optical spectra of BeSS database of these stars and found that the variability of the Hα profile is correlated with the evolution and stages of stability in Be star disks. In our case, we could say that γ Cas and φ Per have circumstellar disks stable with a high density, which have remained almost constant. By contrast the remarkable variability of Hα profile for star 28 Tau lead us to believe that its disk has had episodes of dissipation and slight changes in density. All these results are in agreement with previous studies for different Be stars, confirming the mentioned aspects as general indicators of density changes suffered by circumstellar disks of Be stars.
