59 research outputs found
The origin of interstellar asteroidal objects like 1I/2017 U1 'Oumuamua
We study the origin of the interstellar object 1I/2017 U1 'Oumuamua by
juxtaposing estimates based on the observations with simulations. We speculate
that objects like 'Oumuamua are formed in the debris disc as left over from the
star and planet formation process, and subsequently liberated. The liberation
process is mediated either by interaction with other stars in the parental
star-cluster, by resonant interactions within the planetesimal disc or by the
relatively sudden mass loss when the host star becomes a compact object.
Integrating backward in time in the Galactic potential together with stars from
the Gaia-TGAS catalogue we find that about 1.3Myr ago 'Oumuamua passed the
nearby star HIP 17288 within a mean distance of pc. By comparing nearby
observed L-dwarfs with simulations of the Galaxy we conclude that the
kinematics of 'Oumuamua is consistent with relatively young objects of
--Gyr. We just met 'Oumuamua by chance, and with a derived mean
Galactic density of similarly sized objects within
100\,au from the Sun or per cubic parsec we expect about 2 to 12
such visitors per year within 1au from the Sun.Comment: MNRAS (in press
The consequences of a nearby supernova on the early Solar System
If the Sun was born in a relatively compact open cluster, it is quite likely
that a massive (10MSun) star was nearby when it exploded in a supernova. The
repercussions of a supernova can be rather profound, and the current Solar
System may still bear the memory of this traumatic event. The truncation of the
Kuiper belt and the tilt of the ecliptic plane with respect to the Sun's
rotation axis could be such signatures. We simulated the effect of a nearby
supernova on the young Solar System using the Astronomical Multipurpose
Software Environment. Our calculations are realized in two subsequent steps in
which we study the effect of the supernova irradiation on the circumstellar
disk and the effect of the impact of the nuclear blast-wave which arrives a few
decades later. We find that the blastwave of our adopted supernova exploding at
a distance of --\,pc and at an angle of -- with
respect to the angular-momentum axis of the circumsolar disk would induce a
misalignment between the Sun's equator and its disk to ,
consistent with the current value. The blast of a supernova truncates the disk
at a radius between and \,au, which is consistent with the current
edge of the Kuiper belt. For the most favored parameters, the irradiation by
the supernova as well as the blast wave heat the majority of the disk to \,K, which is sufficiently hot to melt chondrules in the circumstellar
disk. The majority of planetary system may have been affected by a nearby
supernova, some of its repercussions, such as truncation and tilting of the
disk, may still be visible in their current planetary system's topology. The
amount of material from the supernova blast wave that is accreted by the
circumstellar disk is too small by several orders of magnitude to explain the
current abundance of the short live radionuclide Al.Comment: Accepted for publication in A&
Non-intrusive hierarchical coupling strategies for multi-scale simulations in gravitational dynamics
Hierarchical code coupling strategies make it possible to combine the results
of individual numerical solvers into a self-consistent symplectic solution. We
explore the possibility of allowing such a coupling strategy to be
non-intrusive. In that case, the underlying numerical implementation is not
affected by the coupling itself, but its functionality is carried over in the
interface. This method is efficient for solving the equations of motion for a
self-gravitating system over a wide range of scales. We adopt a dedicated
integrator for solving each particular part of the problem and combine the
results to a self-consistent solution. In particular, we explore the
possibilities of combining the evolution of one or more microscopic systems
that are embedded in a macroscopic system. The here presented generalizations
of Bridge include higher-order coupling strategies (from the classic 2nd order
up to 10th-order), but we also demonstrate how multiple bridges can be nested
and how additional processes can be introduced at the bridge time-step to
enrich the physics, for example by incorporating dissipative processes. Such
augmentation allows for including additional processes in a classic Newtonian
N-body integrator without alterations to the underlying code. These additional
processes include for example the Yarkovsky effect, dynamical friction or
relativistic dynamics. Some of these processes operate on all particles whereas
others apply only to a subset.
The presented method is non-intrusive in the sense that the underlying
methods remain operational without changes to the code (apart from adding the
get- and set-functions to enable the bridge operator). As a result, the
fundamental integrators continue to operate with their internal time step and
preserve their local optimizations and parallelism.
... abridged ...Comment: Accepted for publication in Communications in Nonlinear Science and
Numerical Simulation (CNSNS) The associated software is part of the AMUSE
framework and can be downloaded from http:www.amusecode.or
High-resolution superparameterization of OpenIFS with DALES
Poster about superparameterization of clouds, convection and turbulence in the global atmospheric model OpenIFS, using DALES, a high-resolution, three-dimensional large-eddy simulation code
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