AMBER/VLTI and MIDI/VLTI spectro-interferometric observations of the B[e] supergiant CPD-57\deg2874. Size and geometry of the circumstellar envelope in the near- and mid-IR
Domiciano de Souza, A
Astronomy and Astrophysics
© ESO 2007
We present the first high spatial and spectral resolution observations of the circumstellar envelope (CSE) of a B[e] supergiant (CPD−57◦ 2874), performed with the Very Large Telescope Interferometer (VLTI). Spectra, visibilities and closure phase were obtained using the beam-combiner instruments AMBER (near-IR interferometry with three 8.3 m Unit Telescopes or UTs) and MIDI (mid-IR interferometry with two UTs). The interferometric observations of the CSE are well fitted by an elliptical Gaussian model with FWHM diameters varying linearly with wavelength. Typical diameters measured are 1.8 × 3.4 mas or 4.5 × 8.5 AU (adopting a distance of 2.5 kpc) at 2.2 µm, and 12 × 15 mas or 30 × 38 AU at 12 µm. The size of the region emitting the Brγ flux is 2.8 × 5.2 mas or 7.0 × 13.0 AU. The major-axis position angle of the elongated CSE in the mid-IR (144◦) agrees well with previous polarimetric data, hinting that the hot-dust emission originates in a disk-like structure. In addition to the interferometric observations we also present new optical (UBVRcIc) and near-IR (JHKL) broadband photometric observations of CPD−57◦ 2874. Our spectro-interferometric VLTI observations and data analysis support the non-spherical CSE paradigm for B[e] supergiants.
A.D.S. acknowledges the Max-Planck-Institut f¨r Radioastronomie for a postdoctoral fellowship. We are indebted to Dr. R. V. Yudin for his calculations on the intrinsic polarization vector.The preparation and interpretation of AMBER observations benefit from the tools developed by the Jean-Marie Mariotti Center for optical interferometry (JMMC) and from the databases of the Centre de Données Stellaires (CDS) and of the Smithsonian/NASA Astrophysics Data System (ADS). The data reduction software amdlib and the user-friendly interface ammyorick used in this work
This is the author accepted manuscript. The final version is available from EDP Sciences via the DOI in this record.
Astronomy and Astrophysics, 2007,Vol. 464, Number 1, pp. 81-86