Orbital dynamics in the GG Tau A system: investigating its enigmatic disc
arxiv(2024)
摘要
GG Tau is one of the most studied multiple young stellar systems: GG Tau A is
a hierarchical triple surrounded by a massive disc and its companion, GG Tau B,
is also a binary. Despite numerous observational attempts, an understanding of
the geometry of the GG Tau A system is still elusive. We provide new
astrometric measures of the system and we run a set of hydrodynamical
simulations with two representative orbits to test how they impact a disc
composed of dust and gas. We test the dynamical evolution of the two scenarios
on short and long timescales. We obtain synthetic flux emission from our
simulations and we compare them with 1300 μm ALMA dust continuum emission
and 1.67 μm SPHERE dust scattering images to infer the most likely orbital
arrangement. We extend the analysis of the binary orbital parameters using six
new epochs from archival data, showing that the current measurements alone are
not capable of breaking the degeneracy between families of coplanar and
misaligned orbits. We found that the time-scale for the onset of the disc
eccentricity growth, τ_ecc, is a fundamental time-scale for the
morphology of the system. Results from numerical simulations show that the best
match between is obtained with the misaligned configuration (Δθ=
30^∘) on timescales shorter than τ_ecc. The results exhibit an
almost circular cavity and dust ring. However, for both scenarios, the cavity
size and its eccentricity quickly grow for timescales longer than τ_ecc
and the models do not reproduce the observed morphology anymore. This implies
that either the age of the system is shorter than τ_ecc or that the disc
eccentricity growth is not triggered or dissipated. This finding raises
questions on the future evolution of the GG Tau A system and, more in general,
on the time evolution of eccentric binaries and their circumbinary discs.
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