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arXiv · 1201.2420

On the nature of the Herbig B[e] star binary system V921 Scorpii: Discovery of a close companion and relation to the large-scale bipolar nebula

Stefan Kraus·Nuria Calvet·Lee Hartmann·Karl-Heinz Hofmann·Alexander Kreplin·John D. Monnier·Gerd Weigelt
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Abstract

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.

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Stefan Kraus, Nuria Calvet, Lee Hartmann, Karl-Heinz Hofmann, Alexander Kreplin, John D. Monnier, Gerd Weigelt. 2012-01-11. On the nature of the Herbig B[e] star binary system V921 Scorpii: Discovery of a close companion and relation to the large-scale bipolar nebula. https://doi.org/10.1088/2041-8205%2F746%2F1%2Fl2

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