A star disrupted by a stellar black hole as the origin of the cloud falling toward the Galactic center

Understand

We propose that the cloud moving on a highly eccentric orbit near the central black hole in our Galaxy, reported by Gillessen et al., is formed by a photoevaporation wind originating in a disk around a star that is tidally perturbed and shocked at every peribothron passage.

• The disk is proposed to have formed when a stellar black hole flew by the star, tidally disrupted its envelope, and placed the star on its present orbit with some of the tidal debris forming a disk.
• A disrupting encounter at the location of the observed cloud is most likely to be caused by a stellar black hole because of the expected dynamical mass segregation; the rate of these disk-forming encounters may be as high as $\sim 10^{-6}$ per year.
• The star should also be spun up by the encounter, so the disk may subsequently expand by absorbing angular momentum from the star.