These stars are helium-rich and occasionally see their light decrease by several magnitudes. It is thought that dust clouds pass in front of the main star, but no one knows how and why such clouds orbit around the central star. Knowing the location of these clouds already bring valuable information about these poorly understood objects.
That paper measures the size of the shell around V854 Cen. This was feasible only thanks to the extreme resolving power of the VLTI, ten times sharper than what an 8m telescope can resolve. We also found out that the shell is slightly flattened, making it even more intriguing. A model of dust clouds orbiting around the central star was also matched to our data, but it is hard to conclude if the shell is really made of individual clouds or not.
This work is published in Astronomy and Astrophysics.
You can access to the paper data V854 dataset