VLTI/MIDI observations of 7 classical Be stars
Context: Classical Be stars are hot non-supergiant stars surrounded by a gaseous circumstellar envelope that is responsible for the observed IR-excess and emission lines. The origin of this envelope, its geometry, and kinematics have been debated for some time. <BR />Aims: We measured the mid-infrared extension of the gaseous disk surrounding seven of the closest […]
Is the Critical Rotation of Be Stars Really Critical for the Be Phenomenon?
We aim to study the effect of the fast rotation, stellar wind and circumstellar disks around active hot stars and their effects on the formation and evolution of these massive stars. For that purpose, we obtained, for the first time, interferometric measurements of three active hot stars, namely α Arae, κ CMa and Achernar, using […]
The environment of the fast rotating star Achernar. II. Thermal infrared interferometry with VLTI/MIDI
Context: As is the case of several other Be stars, Achernar is surrounded by an envelope, recently detected by near-IR interferometry. <BR />Aims: We search for the signature of circumstellar emission at distances of a few stellar radii from Achernar, in the thermal IR domain. <BR />Methods: We obtained interferometric observations on three VLTI baselines […]
The complex environment of the fast rotating star Achernar
We report recent observations of Achernar ($alpha$~Eri) and its circumstellar environment obtained with interferometric and single-telescope techniques. We also briefly summarize the SIMECA modeling of the near-infrared polar envelope detected by interferometry around this star. From these results, the close environment of Achernar appears to be shaped at least by the fast stellar wind pushed […]
The origin of hydrogen line emission for five Herbig Ae/Be stars spatially resolved by VLTI/AMBER spectro-interferometry
Context: Accretion and outflow processes are of fundamental importance for our understanding of the formation of stars and planetary systems. To trace these processes, diagnostic spectral lines such as the Brγ 2.166 μm line are widely used, although due to a lack of spatial resolution, the origin of the line emission is still unclear. <BR […]
δ Centauri: a new binary Be star detected by VLTI/AMBER spectro-interferometry
Aims: We study the Be star δ Cen circumstellar disk using long-baseline interferometry which is the only observing technique capable of resolving spatially and spectroscopically objects smaller than 5 mas in the H and K band. <BR />Methods: We used the VLTI/AMBER instrument on January 6, 8, and 9, 2008, in the H and K […]
Disk and wind evolution of Achernar: the breaking of the fellowship
Aims: We use spectral energy distributions (SEDs), Hα line profiles, and visibilities available in the literature to study Achernar’s envelope geometry and to propose a possible scenario for its circumstellar disk formation and dissipation. <BR />Methods: We use the SIMECA code to investigate possible geometries of the circumstellar environment by comparing our synthetic results with […]
First MIDI Observations of a Be Star: α Ara
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VEGA: A Visible Spectrograph and Polarimeter for the VLTI
The ESO/VLTI has now clearly a position of world leader in the domain of ground-based optical interferometry. With four 8.2 m telescopes and two (four) 1.8 m telescopes, the Paranal Observatory is without any doubt the best optical interferometric facility in the world. Since many years, it has attracted the major part of the European […]
Disentangling the Wind and the Disk in the Close Surrounding of the Young Stellar Object MWC297 with AMBER/VLTI
The young stellar object MWC297 is a B1.5Ve star exhibiting strong hydrogen emission lines. This object has been observed by the AMBER/VLTI instrument in 2-telescope mode in a sub-region of the K spectral band centered around the Brγ line at 2.1656μm. The object has not only been resolved in the continuum with a visibility of […]