Next talk:

Tuesday, April 3, 2012,  2 PM.
Auditorio de la Facultad de Ciencias
Dr. Nikolaus Vogt
Group 07 Meeting, Students Licenciatura en Fisica Mención Astronomía 

To be determined
Auditorio de la Facultad de Ciencias.
Dr.  Samer Kanaan
Investigador Posdoctoral
PhD. Université de Nice Sophia-Antipolis, Francia.
"Stellar interferometry and its contribution to the study of Be and B[e] phenomen"
Be and B[e] stars exhibit infrared excess and emission lines in their spectra due to the presence of a circumstellar environment of gas and/or dust. Although they have common points their circumstellar environments are very different. In the case of Be stars the gaseous environment is often optically thin, whereas the dusty environment of B [e] stars is often optically thick. Many mechanisms to explain the ejection of matter from the photosphere were proposed such like the fast rotation, non-radial pulsations, radiative winds or binarity. This last one is the more likely scenario for B [e] stars, since they are not critical rotators as Be stars, and because it also allows the formation and the survival of their circumstellar environment on long term time scales. The lack of angular resolution in observations limited the study of these objects and  their modelling was based only on fitting the SED or line profiles. To discriminate between the various physical processes describing the mass loss and the distribution  of matter in the circumstellar medium, the geometry and the kinematics of these envelopes have to be fully constrained. This cannot be done by a single telescope and  ong-baseline interferometry is the only available technique to reach the spatial resolution necessary to resolve most of the envelopes. The VLTI instruments  AMBER (near IR 1-2.5 μm) and MIDI (mid IR 8-13 μm) are perfectly adapted to the study of these gaseous and dusty environments as their flux is generally dominated by  circumstellar emission beyond 1 μm.