VLTI/MIDI observations of 7 classical Be stars

Abstract

We measured the mid-infrared extension of the gaseous disk surrounding seven Be stars in order to constrain the geometry of their circumstellar environments and to try to infer physical parameters characterizing these disks. We used the VLTI/MIDI instrument with baselines up to 130 m to obtain an angular resolution of about 15 mas in the N band and compared our results with previous K band measurements obtained with the VLTI/AMBER instrument and/or the CHARA interferometer. We obtained one calibrated visibility measurement for each of the four stars, p Car, zeta Tau, kappa CMa, and alpha Col, two for delta Cen and beta CMi, and three for alpha Ara. Almost all targets remain unresolved even with the largest VLTI baseline of 130m, evidence that their circumstellar disk extension is less than 10 mas. The only exception is alpha Ara, which is clearly resolved and well-fitted by an elliptical envelope with a major axis a=5.8+-0.8mas and an axis ratio a/b=2.4+-1 at 8 microns. This extension is similar to the size and flattening measured with the VLTI/AMBER instrument in the K band at 2 microns. The size of the circumstellar envelopes for these classical Be stars does not seem to vary strongly on the observed wavelength between 8 and 12microns. Moreover, the size and shape of Alpha Ara's disk is almost identical at 2, 8, and 12microns.

References in corpus (5)

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Cited by in corpus (15)

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• First spectro-interferometric survey of Be stars I. Observations and constraints on the disks geometry and kinematics
• Gas Distribution, Kinematics, and Excitation Structure in the Disks around the Classical Be Stars Beta Canis Minoris and Zeta Tauri
• Dynamical Evolution of Viscous Disks around Be Stars. II : polarimetry
• The Infrared Continuum Sizes of Be Star Disks
• Resolving the dusty circumstellar environment of the A[e] supergiant HD 62623 with the VLTI/MIDI
• Spectro-interferometric observations of a sample of Be stars. Setting limits to the geometry and kinematics of stable Be disks
• Multitechnique testing of the viscous decretion disk model I. The stable and tenuous disk of the late-type Be star $\beta$ CMi
• VLTI-MATISSE L- and N-band aperture-synthesis imaging of the unclassified B[e] star FS Canis Majoris
• Magnetorotational instability in decretion disks of critically rotating stars and the outer structure of Be and Be/X-ray disks
• Visible and near-infrared spectro-interferometric analysis of the edge-on Be star $o$ Aquarii
• The Temperature Structure of Be Star Disks in the Small Magellanic Cloud
• Statistical Analysis of Interferometric Measurements of Axis Ratios for Classical Be Stars