Circumbinary discs with radiative cooling and embedded planets. (arXiv:1905.08631v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Kley_W/0/1/0/all/0/1">Wilhelm Kley</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Thun_D/0/1/0/all/0/1">Daniel Thun</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Penzlin_A/0/1/0/all/0/1">Anna B.T. Penzlin</a> (University of Tuebingen, Germany)
As of today ten circumbinary planets orbiting solar type main sequence stars
have been discovered. Nearly all of them orbit around the central binary very
closely to the region of instability where it is difficult to form them in
situ. It is assumed that they formed further out and migrated to their observed
position. We extend previous studies to a more realistic thermal disc structure
and determine what parameter influence the final parking location of a planet
around a binary star. We perform two-dimensional numerical simulations of
viscous accretion discs around a central binary that include viscous heating
and radiative cooling from the disc surfaces. We vary the binary eccentricity
as well as disc viscosity and mass. Concerning the disc evolution we find that
it can take well over 100000 binary orbits until an equilibrium state is
reached. As seen previously, we find that the central cavity opened by the
binary becomes eccentric and precesses slowly in a prograde sense. Embedded
planets migrate to the inner edge of the disc. In cases of lower disc viscosity
they migrate further in maintaining a circular orbit, while for high viscosity
they are parked further out on an eccentric orbit. The final location of an
embedded planet is linked to its ability to open a gap in the disc. Gap opening
planets separate inner from outer disc, preventing eccentricity excitation in
the latter and making it more circular. This allows embedded planets to migrate
closer to the binary, in agreement with the observations. The necessary
condition for gap opening and the final planet position depend on the planet
mass and disc viscosity.
As of today ten circumbinary planets orbiting solar type main sequence stars
have been discovered. Nearly all of them orbit around the central binary very
closely to the region of instability where it is difficult to form them in
situ. It is assumed that they formed further out and migrated to their observed
position. We extend previous studies to a more realistic thermal disc structure
and determine what parameter influence the final parking location of a planet
around a binary star. We perform two-dimensional numerical simulations of
viscous accretion discs around a central binary that include viscous heating
and radiative cooling from the disc surfaces. We vary the binary eccentricity
as well as disc viscosity and mass. Concerning the disc evolution we find that
it can take well over 100000 binary orbits until an equilibrium state is
reached. As seen previously, we find that the central cavity opened by the
binary becomes eccentric and precesses slowly in a prograde sense. Embedded
planets migrate to the inner edge of the disc. In cases of lower disc viscosity
they migrate further in maintaining a circular orbit, while for high viscosity
they are parked further out on an eccentric orbit. The final location of an
embedded planet is linked to its ability to open a gap in the disc. Gap opening
planets separate inner from outer disc, preventing eccentricity excitation in
the latter and making it more circular. This allows embedded planets to migrate
closer to the binary, in agreement with the observations. The necessary
condition for gap opening and the final planet position depend on the planet
mass and disc viscosity.
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