Accretion Disks around Massive Protostars

01/10/2018 to 30/09/2022

Observations indicate a clear trend of increasing multiplicity with increasing mass of the primary star. Additional to visual companions, many massive stars are surrounded by short-period spectroscopic binaries. Orbital periods shorter than a few days are not uncommon.
Nonetheless, the formation mechanism of close massive binary stars are unknown. Both stars might form independently of each other and get together later on in a capturing event. But the high frequency of close pairs with components of similar mass argues in favor of a multiplicity originating from the formation process rather than from a tidal capture in a dense cluster.
In a classical static disk fragmentation analysis, gravitational instabilities at these small radii are suppressed due to the hot temperature and fast Keplerian ro- tation of the inner disk. But our previous dynamical studies of disk formation around high-mass stars suggest a strong increase of the fragmentation probability behind the dust sublimation front of the massive accretion disk. Shadowed cool regions behind the dust sublimation radius might represent the birth place of close companions with a semi-major axis of a few up to 100 au. Furthermore, migration of the secondary star due to its interaction with the accretion disk would explain short-period, spectroscopic binaries with sub-AU semi-major axes.
The proposed project targets at direct numerical modeling of the formation and evolution of massive accretion disks with a focus on gravitational instabilities behind the dust sublimation front.