4,248 research outputs found
Toward a Deterministic Model of Planetary Formation VII: Eccentricity Distribution of Gas Giants
The ubiquity of planets and diversity of planetary systems reveal planet
formation encompass many complex and competing processes. In this series of
papers, we develop and upgrade a population synthesis model as a tool to
identify the dominant physical effects and to calibrate the range of physical
conditions. Recent planet searches leads to the discovery of many
multiple-planet systems. Any theoretical models of their origins must take into
account dynamical interaction between emerging protoplanets. Here, we introduce
a prescription to approximate the close encounters between multiple planets. We
apply this method to simulate the growth, migration, and dynamical interaction
of planetary systems. Our models show that in relatively massive disks, several
gas giants and rocky/icy planets emerge, migrate, and undergo dynamical
instability. Secular perturbation between planets leads to orbital crossings,
eccentricity excitation, and planetary ejection. In disks with modest masses,
two or less gas giants form with multiple super-Earths. Orbital stability in
these systems is generally maintained and they retain the kinematic structure
after gas in their natal disks is depleted. These results reproduce the
observed planetary mass-eccentricity and semimajor axis-eccentricity
correlations. They also suggest that emerging gas giants can scatter residual
cores to the outer disk regions. Subsequent in situ gas accretion onto these
cores can lead to the formation of distant (> 30AU) gas giants with nearly
circular orbits.Comment: 54 pages, 14 Figures; accepted for publication in Astrophysical
Journa
How Do Nonlinear Voids Affect Light Propagation ?
Propagation of light in a clumpy universe is examined. As an inhomogeneous
matter distribution, we take a spherical void surrounded by a dust shell where
the ``lost mass'' in the void is compensated by the shell. We study how the
angular-diameter distance behaves when such a structure exists. The
angular-diameter distance is calculated by integrating the Raychaudhuri
equation including the shear. An explicit expression for the junction condition
for the massive thin shell is calculated. We apply these results to a dust
shell embedded in a Friedmann universe and determine how the distance-redshift
relation is modified compared with that in the purely Friedmann universe. We
also study the distribution of distances in a universe filled with voids. We
show that the void-filled universe gives a larger distance than the FRW
universe by at if the size of the void is of the
Horizon radius.Comment: To appear in Prog. Theor. Phys. 10
Formation of Hot Planets by a combination of planet scattering, tidal circularization, and Kozai mechanism
We have investigated the formation of close-in extrasolar giant planets
through a coupling effect of mutual scattering, Kozai mechanism, and tidal
circularization, by orbital integrations. We have carried out orbital
integrations of three planets with Jupiter-mass, directly including the effect
of tidal circularization. We have found that in about 30% runs close-in planets
are formed, which is much higher than suggested by previous studies. We have
found that Kozai mechanism by outer planets is responsible for the formation of
close-in planets. During the three-planet orbital crossing, the Kozai
excitation is repeated and the eccentricity is often increased secularly to
values close enough to unity for tidal circularization to transform the inner
planet to a close-in planet. Since a moderate eccentricity can remain for the
close-in planet, this mechanism may account for the observed close-in planets
with moderate eccentricities and without nearby secondary planets. Since these
planets also remain a broad range of orbital inclinations (even retrograde
ones), the contribution of this process would be clarified by more observations
of Rossiter-McLaughlin effects for transiting planets.Comment: 15 pages, 16 figures, Accepted for publication in Ap
Tipe-tipe Budaya Perusahaan dan Pengaruhnya terhadap Kepuasan Kerja Pegawai Telkom Uner III Bandung
Free-floating planets from core accretion theory: microlensing predictions
We calculate the microlensing event rate and typical time-scales for the
free-floating planet (FFP) population that is predicted by the core accretion
theory of planet formation. The event rate is found to be ~
of that for the stellar population. While the stellar microlensing event
time-scale peaks at around 20 days, the median time-scale for FFP events (~0.1
day) is much shorter. Our values for the event rate and the median time-scale
are significantly smaller than those required to explain the \cite{Sum+11}
result, by factors of ~13 and ~16, respectively. The inclusion of planets at
wide separations does not change the results significantly. This discrepancy
may be too significant for standard versions of both the core accretion theory
and the gravitational instability model to explain satisfactorily. Therefore,
either a modification to the planet formation theory is required, or other
explanations to the excess of short-time-scale microlensing events are needed.
Our predictions can be tested by ongoing microlensing experiment such as
KMTNet, and by future satellite missions such as WFIRST and Euclid.Comment: 6 pages, 5 figures, MNRAS in pres
Toward a Deterministic Model of Planetary Formation VI: Dynamical Interaction and Coagulation of Multiple Rocky Embryos and Super-Earth Systems around Solar Type Stars
Radial velocity and transit surveys indicate that solar-type stars bear
super-Earths, with mass and period up to ~ 20 M_E and a few months, are more
common than those with Jupiter-mass gas giants. In many cases, these
super-Earths are members of multiple-planet systems in which their mutual
dynamical interaction has influenced their formation and evolution. In this
paper, we modify an existing numerical population synthesis scheme to take into
account protoplanetary embryos' interaction with their evolving natal gaseous
disk, as well as their close scatterings and resonant interaction with each
other. We show that it is possible for a group of compact embryos to emerge
interior to the ice line, grow, migrate, and congregate into closely-packed
convoys which stall in the proximity of their host stars. After the disk-gas
depletion, they undergo orbit crossing, close scattering, and giant impacts to
form multiple rocky Earths or super-Earths in non-resonant orbits around ~
0.1AU with moderate eccentricities of ~0.01-0.1. We suggest that most
refractory super-Earths with period in the range of a few days to weeks may
have formed through this process. These super-Earths differ from Neptune-like
ice giants by their compact sizes and lack of a substantial gaseous envelope.Comment: 37 pages, 10 figures, accepted for publication in Ap
Planet Population Synthesis
With the increasing number of exoplanets discovered, statistical properties
of the population as a whole become unique constraints on planet formation
models provided a link between the description of the detailed processes
playing a role in this formation and the observed population can be
established. Planet population synthesis provides such a link. The approach
allows to study how different physical models of individual processes (e.g.,
proto-planetary disc structure and evolution, planetesimal formation, gas
accretion, migration, etc.) affect the overall properties of the population of
emerging planets. By necessity, planet population synthesis relies on
simplified descriptions of complex processes. These descriptions can be
obtained from more detailed specialised simulations of these processes. The
objective of this chapter is twofold: 1) provide an overview of the physics
entering in the two main approaches to planet population synthesis and 2)
present some of the results achieved as well as illustrate how it can be used
to extract constraints on the models and to help interpret observations.Comment: 23 pages, 8 figures, accepted for publication as a chapter in
Protostars and Planets VI, University of Arizona Press (2014), eds. H.
Beuther, R. Klessen, C. Dullemond, Th. Henning. Updated references relative
to v
Migrasi Simbolik Wacana Kuasa Tubuh: Menguak Wacana Tubuh Dalam Ode Untuk Leopold Von Sacher-Masoch Karya Dinar Rahayu
The presence of Indonesian women writers with the dominant discourse of the power of body, presenting the pros and cons that would not go over. Female body is the language of women that can be poured through the writing of literary works. Helene Cixous brought the spirit of "writing the body" to motivate women authors to express himself through written discourse, which so far has been dominated by men. Cixous spirit is also promoted by Dinar Rahayu appear in the novel Ode untuk Leopold Von Sacher-Masoch. Dinar Rahayu voicing complexity of urban women's voices in this novel through several migration symbolic of the power of the female body. Migration is enriched by the presence of symbolic power in a sound body of Greek and Scandinavian mythology and Leopold voices in his work Venus in Furs. Through in-depth reading on the symbolic migration brought to the Ode untuk Leopold Von Sacher-Masoch through the voices of the characters and the particularities of naration techniques can be seen that this novel (as well as other sexist novels) is not merely a commodity that exploit sexuality pornography but rather an attempt to author urban female voices will be the "body power". This study uses content analysis method that begins with the reading of literature, heuristic and hermeneutic, and take advantage of intertextuality approach
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