EDP Sciences
AMBER: Instrument description and first astrophysical results
Press Release
Free Access
Volume 464, Number 1, March II 2007
AMBER: Instrument description and first astrophysical results
Page(s) 81 - 86
DOI https://doi.org/10.1051/0004-6361:20054134

A&A 464, 81-86 (2007)
DOI: 10.1051/0004-6361:20054134

AMBER/VLTI and MIDI/VLTI spectro-interferometric observations of the B[e] supergiant CPD $-57\mathrm{^\circ}\,2874$

Size and geometry of the circumstellar envelope in the near- and mid-IR
A. Domiciano de Souza1, 2, T. Driebe1, O. Chesneau3, K.-H. Hofmann1, S. Kraus1, A.S. Miroshnichenko1, 4, K. Ohnaka1, R.G. Petrov2, T. Preisbisch1, P. Stee3, G. Weigelt1, F. Lisi5, F. Malbet6, and A. Richichi7

1  Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
2  Laboratoire Universitaire d'Astrophysique de Nice, UMR 6525 Université de Nice - Sophia Antipolis/CNRS, Parc Valrose, 06108 Nice Cedex 2, France
3  Laboratoire Gemini, UMR 6203 Observatoire de la Côte d'Azur/CNRS, BP 4229, 06304 Nice Cedex 4, France
4  Dept. of Physics and Astronomy, PO Box 26170, University of North Carolina at Greensboro, Greensboro, NC 27402 6170, USA
5  INAF-Osservatorio Astrofisico di Arcetri, Istituto Nazionale di Astrofisica, Largo E. Fermi 5, 50125 Firenze, Italy
6  Laboratoire d'Astrophysique de Grenoble, UMR 5571 Université Joseph Fourier/CNRS, BP 53, 38041 Grenoble Cedex 9, France
7  European Southern Observatory, Karl Schwarzschild Strasse 2, 85748 Garching, Germany

(Received 31 August 2005 / Accepted 17 October 2005 )

We present the first high spatial and spectral resolution observations of the circumstellar envelope (CSE) of a B[e] supergiant (CPD $-57{^\circ}\,2874$), 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 $\simeq$ $1.8\times3.4$ mas or $\simeq$ $4.5\times8.5$ AU (adopting a distance of 2.5 kpc) at $2.2\,\mu{\rm m}$, and $\simeq$ $12\times15$ mas or $\simeq$ $30\times38$ AU at $12\,\mu{\rm m}$. The size of the region emitting the Br$\gamma$ flux is $\simeq$ $2.8\times5.2$ mas or $\simeq$ $7.0\times13.0$ AU. The major-axis position angle of the elongated CSE in the mid-IR ($\simeq$ $144{^\circ}$) 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 ( $UBVR_{\rm c}I_{\rm c}$) and near-IR ($\it JHKL$) broadband photometric observations of CPD $-57{^\circ}\,2874$. Our spectro-interferometric VLTI observations and data analysis support the non-spherical CSE paradigm for B[e] supergiants.

Key words: techniques: high angular resolution -- techniques: interferometric -- infrared: stars -- stars: early-type -- stars: emission-line, Be -- stars: mass-loss

© ESO 2007