Choked accretion: from radial infall to bipolar outflows by breaking spherical symmetry
Por:
Aguayo-Ortiz, Alejandro, Tejeda, Emilio, Hernandez, X.
Publicada:
1 dic 2019
Resumen:
Steady-state, spherically symmetric accretion flows are well understood
in terms of the Bondi solution. Spherical symmetry, however, is
necessarily an idealized approximation to reality. Here we explore the
consequences of deviations away from spherical symmetry, first through a
simple analytic model to motivate the physical processes involved, and
then through hydrodynamical, numerical simulations of an ideal fluid
accreting on to a Newtonian gravitating object. Specifically, we
consider axisymmetric, large-scale, small-amplitude deviations in the
density field such that the equatorial plane is overdense as compared to
the polar regions. We find that the resulting polar density gradient
dramatically alters the Bondi result and gives rise to steady-state
solutions presenting bipolar outflows. As the density contrast
increases, more and more material is ejected from the system, attaining
speeds larger than the local escape velocities for even modest density
contrasts. Interestingly, interior to the outflow region, the flow tends
locally towards the Bondi solution, with a resulting total mass
accretion rate through the inner boundary choking at a value very close
to the corresponding Bondi one. Thus, the numerical experiments
performed suggest the appearance of a maximum achievable accretion rate,
with any extra material being ejected, even for very small departures
from spherical symmetry.
Filiaciones:
Aguayo-Ortiz, Alejandro:
Univ Nacl Autonoma Mexico, Inst Astron, AP 70-264, Mexico City 04510, DF, Mexico
Tejeda, Emilio:
Univ Michoacana, Inst Fis & Matemat, Catedras CONACyT, Edificio C-3,Ciudad Univ, Morelia, Michoacan, Mexico
Hernandez, X.:
Univ Nacl Autonoma Mexico, Inst Astron, AP 70-264, Mexico City 04510, DF, Mexico
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