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

TL;DR

This paper proposes a model where a star's disk, formed by a black hole's tidal disruption, produces the observed cloud near the Galactic center through photoevaporation, linking stellar encounters to cloud formation.

Contribution

It introduces a novel scenario where a stellar black hole's tidal disruption creates a disk around a star, explaining the cloud's origin and predicting observable signatures.

Findings

The model explains the cloud's highly eccentric orbit and formation process.

Predicts a smaller cloud will form after 2013 peribothron passage.

Suggests increased infrared luminosity from the disk near peribothron.

Abstract

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. Once the disk expands up to the tidal truncation radius, the tidal perturbation of the outer disk edge at every peribothron may place gas streams on larger orbits which can give rise to a photoevaporation wind that forms the cloud at every orbit. This model predicts that, after the cloud is disrupted at the next peribothron passage in 2013, a smaller unresolved cloud will gradually grow around the star on the same present orbit. An increased infrared luminosity from the disk may also be detectable when the peribothron is reached. We also note that this model revives the encounter theory for planet formation.