Resolving the B[e] star Hen 3-1191 at 10
microns with VLTI/MIDI
Lachaume, R., Preibisch, Th., Driebe,
Th., Weigelt, G.
A&A, 469, pg.587-593 (2007)
Abstract
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 40 m
baseline and has an equivalent uniform disc diameter ranging from 24
mas
at 8 microns to 36 mas at 13 microns. 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 (.4-60 microns)
and N-band visibilities. Because of the unknown nature for 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.
At last, 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 to 250 x 10^-4 solar mass per year) and
that of a protoplanetary nebula with an equatorial mass excretion rate
(>~ 4 x 10^-5 solar mass per year). In both cases, taking the
additional
presence of an envelope or wind into account would result in lower mass
flows.
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