Supermassive black holes reside in cores of galaxies, where they are often
surrounded by a nuclear cluster and a clumpy torus of gas and dust. Mutual
interactions can set some stars on a plunging trajectory towards the black
hole. We model the pericentre passage of a dust-enshrouded star during which
the dusty envelope becomes stretched by tidal forces and is affected by the
interaction with the surrounding medium. In particular, we explore under which
conditions these encounters can lead to periods of enhanced accretion activity.
We discuss different scenarios for such a dusty source. To this end, we
employed a modification of the Swift integration package. Elements of the cloud
were modelled as numerical particles that represent the dust component that
interacts with the optically thin gaseous environment. We determine the
fraction of the total mass of the dust component that is diverted from the
original path during the passages through the pericentre at ∼103
Schwarzschild radii and find that the main part of the dust (≳90% of
its mass) is significantly affected upon the first crossing. The fraction of
mass captured at the second passage generally decreases to very low values. As
an example, we show predictions for the dusty source evolution assuming the
current orbital parameters of the G2 cloud (also known as Dusty S-Cluster
Object, DSO) in our Galactic centre. Encounter of a core-less cloud with a
supermassive black hole is, most likely, a non-repeating event: the cloud is
destroyed. However, in the case of a dust-enshrouded star, part of the envelope
survives the pericentre passage. We discuss an offset of ≲0.3 arcsec
between the centre of mass of the diverted part and the star along the
eccentric orbit. Finally, we examine an interesting possibility of a binary
star embedded within a common wind envelope that becomes dispersed at the
pericentre passage.Comment: 18 pages, 15 figures, Astronomy and Astrophysics accepte
