Time, spatial, and spectral resolution of the Hα line-formation region of Deneb and Rigel with the VEGA/CHARA interferometer
Context. BA-type supergiants are amongst the most optically-bright stars. They are observable in extragalactic environments, hence potential accurate distance indicators. <BR /> Aims: An extensive record of emission activity in the Hα line of the BA supergiants β Orionis (Rigel, B8Ia) and α Cygni (Deneb, A2Ia) is indicative of localized time-dependent mass ejections. However, little […]
Resolving the dusty circumstellar environment of the A[e] supergiant HD 62623 with the VLTI/MIDI
Context. B[e] stars are hot stars surrounded by circumstellar gas and dust which is responsible for the presence of emission lines and IR-excess in their spectra. How dust can be formed in this highly illuminated and diluted environment remains an open issue. <BR /> Aims: HD 62623 is one of the very few A-type supergiants […]
The galactic unclassified B[e] star HD 50138. I. A possible new shell phase
Context: The observed spectral variation of HD 50138 has led different authors to classify it in a very wide range of spectral types and luminosity classes (from B5 to A0 and III to Ia) and at different evolutionary stages as either HAeBe star or classical Be.<BR /> Aims: Based on new high-resolution optical spectroscopic data […]
Revealing the sub-AU asymmetries of the inner dust rim in the disk around the Herbig Ae star R Coronae Austrinae
Context: Unveiling the structure of the disks around intermediate-mass pre-main-sequence stars (Herbig Ae/Be stars) is essential for our understanding of the star and planet formation process. In particular, models predict that in the innermost AU around the star, the dust disk forms a “puffed-up” inner rim, which should result in a strongly asymmetric brightness distribution […]
A binary engine fuelling HD 87643’s complex circumstellar environment. Determined using AMBER/VLTI imaging
Context: The star HD 87643, exhibiting the “B[e] phenomenon”, has one of the most extreme infrared excesses for this object class. It harbours a large amount of both hot and cold dust, and is surrounded by an extended reflection nebula. <BR />Aims: One of our major goals was to investigate the presence of a companion […]
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 […]
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 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 […]