Astronomy and Astrophysics, volume 469, 587-593 (2007/7-2)
Resolving the B[e] star Hen 3-1191 at 10µm with VLTI/MIDI.
LACHAUME R., PREIBISCH T., DRIEBE T. and WEIGELT G.
Abstract (from CDS):
We report spatially resolved, spectrally dispersed N-band observations of the B[e] star Hen 3-1191 with the MIDI instrument of the Very Large Telescope Interferometer. The object is resolved with a 40m baseline and has an equivalent uniform disc diameter ranging from 24mas at 8µm to 36mas at 13µm. The MIDI spectrum and visibilities show a curvature which can arise from a weak silicate feature in which the object appears ≃15% larger than in the continuum, but this could result from a change in the object's geometry within the band. We then model Hen's 3-1191 spectral energy distribution (.4-60µm) and N-band visibilities. Because of the unknown nature of the object, we use a wide variety of models for objects with IR excesses. We find the observations to be consistent with a disc featuring an unusually high mass accretion and a large central gap almost void of matter, an excretion disc, and a binary made of two IR sources. We are unable to find a circumstellar shell model consistent with the data. We review the different hypotheses concerning the physical nature of the star and conclude that it is neither a Be supergiant nor a symbiotic star. However, we could not discriminate between the scenario of a young stellar object featuring an unusually strong FU Orionis-like outburst of mass accretion (4-250x10–4M☉/yr) and that of a protoplanetary nebula with an equatorial mass excretion rate >4x10–5M☉/yr. In both cases, taking the additional presence of an envelope or wind into account would result in lower mass flows.