- a B-type central star
- emission lines from hydrogen, and forbidden lines
- an infrared excess, related to the presence of dust
Observations of HD 87643 were part of a program started in collaboration with O. Chesneau and R. Petrov. We proposed this target to be observed by the VLTI in 2006 as part of the first open time proposals of the AMBER instrument. Then we observed it again in 2008 during 1.5 night, because the first observations were impaired by a combination of bad luck and low signal-to-noise ratio. This new extensive dataset allowed us to produce one of the first-ever images of the VLTI.
In this image, we could clearly detect a companion star to the main star. In addition, we found extended material around the primary star. We then used a new generation model-fitting tool, whose premises were experienced in a previous paper, to recover the spectra of both stars and the extended material in the system. These spectra exhibit new information on the system, the primary star being a B[e] star : a B-type star surrounded by a gaseous and dusty disk, and the secondary star being an enigmatic compact object enshrouded in a cocoon of dust.
In addition, we could get adaptive optics images of the system, that basically confirm the interferometric view of the system, and wide-field images, which teach us on the recent history of the system. These wide-field images show arc-like structures which appear to have been ejected from the central star at a frequency of few years. A possible explaination would be if the companion star would have a very eccentric orbit, triggering mass ejection from the primary at the periastron passage. In this hypothesis, the orbit of the system would be covered in 10 to 25 years.
The global view of that system is completely changed with these findings. We do not have anymore a single supergiant star expelling its outer shells with rapid rotation, but rather a double system with complex interactions embedded in imbricated shells of dust.
- Read the A&A article
- See the corresponding ESO press release
- Read a following proceeding with new ideas presented on the system
The AMBER data associated to this paper can be downloaded here: AMBER and MIDI data on HD87643.
New observations of that system come in 2012. Stay tuned !