Christopher Broeg, Willy Benz
We describe the growth of gas giant planets in the core accretion scenario.
The core growth is not modeled as a gradual accretion of planetesimals but as
episodic impacts of large mass ratios, i.e. we study impacts of 0.02 - 1 Earth
masses onto cores of 1-15 Earth masses. Such impacts could deliver the majority
of solid matter in the giant impact regime. We focus on the thermal response of
the envelope to the energy delivery. Previous studies have shown that sudden
shut off of core accretion can dramatically speed up gas accretion. We
therefore expect that giant impacts followed by periods of very low core
accretion will result in a net increase in gas accretion rate. This study aims
at modelling such a sequence of events and to understand the reaction of the
envelope to giant impacts in more detail.
To model this scenario, we spread the impact energy deposition over a time
that is long compared to the sound crossing time, but very short compared to
the Kelvin-Helmholtz time. The simulations are done in spherical symmetry and
assume quasi-hydrostatic equilibrium.
Results confirm what could be inferred from previous studies: gas can be
accreted faster onto the core for the same net core growth speed while at the
same time rapid gas accretion can occur for smaller cores -- significantly
smaller than the usual critical core mass. Furthermore our simulations show,
that significant mass fractions of the envelope can be ejected by such an
impact.
View original:
http://arxiv.org/abs/1112.0498
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