Stefan Kraus, Nuria Calvet, Lee Hartmann, Karl-Heinz Hofmann, Alexander Kreplin, John D. Monnier, Gerd Weigelt
Belonging to the group of B[e] stars, V921 Scorpii is associated with a
strong infrared excess and permitted and forbidden line emission, indicating
the presence of low- and high-density circumstellar gas and dust. Many aspects
of V921 Sco and other B[e] stars still remain mysterious, including their
evolutionary state and the physical conditions resulting in the class-defining
characteristics. In this paper, we employ VLTI/AMBER spectro-interferometry in
order to reconstruct high-resolution (lambda/2B=0.0013") model-independent
interferometric images for three wavelength bands around 1.65, 2.0, and 2.3
micrometer. In our images, we discover a close (25.0+/-0.8 milliarcsecond,
corresponding to 29+/-0.9 AU at 1.15 kpc) companion around V921 Sco. Between
two epochs in 2008 and 2009, we measure orbital motion of 7 degrees, implying
an orbital period of about 35 years (for a circular orbit). Around the primary
star, we detect a disk-like structure with indications for a radial temperature
gradient. The polar axis of this AU-scale disk is aligned with the
arcminute-scale bipolar nebula in which V921 Sco is embedded. Using
Magellan/IMACS imaging, we detect multi-layered arc-shaped sub-structure in the
nebula, suggesting episodic outflow activity from the system with a period of
about 25 years, roughly matching the estimated orbital period of the companion.
Our study supports the hypothesis that the B[e] phenomenon is related to
dynamical interaction in a close binary system.
View original:
http://arxiv.org/abs/1201.2420
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