4,364 research outputs found
N-body Simulations of Satellite Formation around Giant Planets: Origin of Orbital Configuration of the Galilean Moons
As the number of discovered extrasolar planets has been increasing, diversity
of planetary systems requires studies of new formation scenarios. It is
important to study satellite formation in circumplanetary disks, which is often
viewed as analogous to formation of rocky planets in protoplanetary disks. We
investigated satellite formation from satellitesimals around giant planets
through N-body simulations that include gravitational interactions with a
circumplanetary gas disk. Our main aim is to reproduce the observable
properties of the Galilean satellites around Jupiter through numerical
simulations, as previous N-body simulations have not explained the origin of
the resonant configuration. We performed accretion simulations based on the
work of Sasaki et al. (2010), in which an inner cavity is added to the model of
Canup & Ward (2002, 2006). We found that several satellites are formed and
captured in mutual mean motion resonances outside the disk inner edge and are
stable after rapid disk gas dissipation, which explains the characteristics of
the Galilean satellites. In addition, owing to the existence of the disk edge,
a radial compositional gradient of the Galilean satellites can also be
reproduced. An additional objective of this study is to discuss orbital
properties of formed satellites for a wide range of conditions by considering
large uncertainties in model parameters. Through numerical experiments and
semianalytical arguments, we determined that if the inner edge of a disk is
introduced, a Galilean-like configuration in which several satellites are
captured into a 2:1 resonance outside the disk inner cavity is almost
universal. In fact, such a configuration is produced even for a massive disk
and rapid type I migration. This result implies the inevitability of a Galilean
satellite formation in addition to providing theoretical predictions for
extrasolar satellites.Comment: 20 pages, 9 figures, accepted for publication in Ap
Fission fragment mass reconstruction from Si surface barrier detector measurement
A method for plasma delay and pulse-height defect corrections for Si surface
barrier detectors (SBD) is presented. Based on known empirical formulae, simple
approximations involving the measured time-of-flight (TOF) and energy of the
ions were found and a mass reconstruction procedure was developed. The
procedure was applied for obtaining the fission fragment mass and angular
distributions from the Ni+Au reaction at 418 MeV and 383 MeV
incident energy using an array of eight SBDs.Comment: 3 pages, 1 table, 3 figures, submitted to NIM A ; 4 pages, 1 table, 5
figures, added discussion and figure
Eccentricity Trap: Trapping of Resonantly Interacting Planets near the Disk Inner Edge
Using orbital integration and analytical arguments, we have found a new
mechanism (an "eccentricity trap") to halt type I migration of planets near the
inner edge of a protoplanetary disk. Because asymmetric eccentricity damping
due to disk-planet interaction on the innermost planet at the disk edge plays a
crucial role in the trap, this mechanism requires continuous eccentricity
excitation and hence works for a resonantly interacting convoy of planets. This
trap is so strong that the edge torque exerted on the innermost planet can
completely halt type I migrations of many outer planets through mutual resonant
perturbations. Consequently, the convoy stays outside the disk edge, as a
whole. We have derived semi-analytical formula for the condition for the
eccentricity trap and predict how many planets are likely to be trapped. We
found that several planets or more should be trapped by this mechanism in
protoplanetary disks that have cavities. It can be responsible for the
formation of non-resonant, multiple, close-in super-Earth systems extending
beyond 0.1AU. Such systems are being revealed by radial velocity observations
to be quite common around solar-type stars.Comment: 24 pages, 7 figures, accepted for publication in Ap
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