Publications of the MPIfR Optical & Infrared Interferometry Group

AMBER/VLTI and VLTI/MIDI spectro-interferometric observations of the B[e] supergiant CPD-57° 2874

A. Domiciano de Souza, T. Driebe, O. Chesneau, K.-H. Hofmann, S. Kraus, A.S. Miroshnichenko, K. Ohnaka, R.G. Petrov, T. Preibisch, P. Stee, G. Weigelt, F. Lisi, F. Malbet, and A. Richichi

Astronomy & Astrophysics, vol.464, pg.81-86 (2007)

Abstract
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.

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