1,849 research outputs found
Habitable Planet Formation in Binary-Planetary Systems
Recent radial velocity observations have indicated that Jovian-type planets
can exist in moderately close binary star systems. Numerical simulations of the
dynamical stability of terrestrial-class planets in such environments have
shown that, in addition to their giant planets, these systems can also harbor
Earth-like objects. In this paper, we study the late stage of terrestrial
planet formation in such binary-planetary systems, and present the results of
the simulations of the formation of Earth-like bodies in their habitable zones.
We consider a circumprimary disk of Moon- to Mars-sized objects and numerically
integrate the orbits of these bodies at the presence of the Jovian-type planet
of the system and for different values of the mass, semimajor axis, and orbital
eccentricity of the secondary star. Results indicate that, Earth-like objects,
with substantial amounts of water, can form in the habitable zone of the
primary star. Simulations also indicate that, by transferring angular momentum
from the secondary star to protoplanetary objects, the giant planet of the
system plays a key role in the radial mixing of these bodies and the water
contents of the final terrestrial planets. We will discuss the results of our
simulation and show that the formation of habitable planets in binary-planetary
systems is more probable in binaries with moderate to large perihelia.Comment: 27 pages, 11 figures, submitted for publicatio
Transit Timing Observations from Kepler: VII. Confirmation of 27 planets in 13 multiplanet systems via Transit Timing Variations and orbital stability
We confirm 27 planets in 13 planetary systems by showing the existence of
statistically significant anti-correlated transit timing variations (TTVs),
which demonstrates that the planet candidates are in the same system, and
long-term dynamical stability, which places limits on the masses of the
candidates---showing that they are planetary. %This overall method of planet
confirmation was first applied to \kepler systems 23 through 32. All of these
newly confirmed planetary systems have orbital periods that place them near
first-order mean motion resonances (MMRs), including 6 systems near the 2:1
MMR, 5 near 3:2, and one each near 4:3, 5:4, and 6:5. In addition, several
unconfirmed planet candidates exist in some systems (that cannot be confirmed
with this method at this time). A few of these candidates would also be near
first order MMRs with either the confirmed planets or with other candidates.
One system of particular interest, Kepler-56 (KOI-1241), is a pair of planets
orbiting a 12th magnitude, giant star with radius over three times that of the
Sun and effective temperature of 4900 K---among the largest stars known to host
a transiting exoplanetary system.Comment: 12 pages, 13 figures, 5 tables. Submitted to MNRA
Dynamical Stability and Habitability of Gamma Cephei Binary-Planetary System
It has been suggested that the long-lived residual radial velocity variations
observed in the precision radial velocity measurements of the primary of Gamma
Cephei (HR8974, HD222404, HIP116727) are likely due to a Jupiter-like planet
around this star (Hatzes et al, 2003). In this paper, the orbital dynamics of
this plant is studied and also the possibility of the existence of a
hypothetical Earth-like planet in the habitable zone of its central star is
discussed. Simulations, which have been carried out for different values of the
eccentricity and semimajor axis of the binary, as well as the orbital
inclination of its Jupiter-like planet, expand on previous studies of this
system and indicate that, for the values of the binary eccentricity smaller
than 0.5, and for all values of the orbital inclination of the Jupiter-like
planet ranging from 0 to 40 degrees, the orbit of this planet is stable. For
larger values of the binary eccentricity, the system becomes gradually
unstable. Integrations also indicate that, within this range of orbital
parameters, a hypothetical Earth-like planet can have a long-term stable orbit
only at distances of 0.3 to 0.8 AU from the primary star. The habitable zone of
the primary, at a range of approximately 3.1 to 3.8 AU, is, however, unstable.Comment: 25 pages, 7 figures, 3 tables, submitted for publicatio
The Detection and Characterization of a Nontransiting Planet by Transit Timing Variations
The Kepler Mission is monitoring the brightness of ~150,000 stars searching
for evidence of planetary transits. As part of the "Hunt for Exomoons with
Kepler" (HEK) project, we report a planetary system with two confirmed planets
and one candidate planet discovered using the publicly available data for
KOI-872. Planet b transits the host star with a period P_b=33.6d and exhibits
large transit timing variations indicative of a perturber. Dynamical modeling
uniquely detects an outer nontransiting planet c near the 5:3 resonance
(P_c=57.0d) of mass 0.37 times that of Jupiter. Transits of a third planetary
candidate are also found: a 1.7-Earth radius super-Earth with a 6.8d period.
Our analysis indicates a system with nearly coplanar and circular orbits,
reminiscent of the orderly arrangement within the solar system.Comment: Accepted for publication in Science. Published online on May 10,
2012. Main Text and supplemental information included in a single merged
file, 58 page
Tidal evolution of exo-planetary systems: WASP-50, GJ 1214 and CoRoT-7
We perform numerical simulations to investigate tidal evolution of two
single-planet systems, that is, WASP-50 and GJ 1214 and a two-planet system
CoRoT-7. The results of orbital evolution show that tidal decay and
circularization may play a significant role in shaping their final orbits,
which is related to the initial orbital data in the simulations. For GJ 1214
system, different cases of initial eccentricity are also considered as only an
upper limit of its eccentricity (0.27) is shown, and the outcome suggests a
possible maximum initial eccentricity (0.4) in the adopted dynamical model.
Moreover, additional runs with alternative values of dissipation factor
are carried out to explore tidal evolution for GJ 1214b, and these
results further indicate that the real of GJ 1214b may be much
larger than its typical value, which may reasonably suggest that GJ 1214b bears
a present-day larger eccentricity, undergoing tidal circularization at a slow
rate. For the CoRoT-7 system, tidal forces make two planets migrating towards
their host star as well as producing tidal circularization, and in this process
tidal effects and mutual gravitational interactions are coupled with each
other. Various scenarios of the initial eccentricity of the outer planet have
also been done to investigate final planetary configuration. Tidal decay
arising from stellar tides may still work for each system as the eccentricity
decreases to zero, and this is in association with the remaining lifetime of
each planet used to predict its future.Comment: 9 pages, 12 figures, accepted for publication in "SCIENCE CHINA
Physics,Mechanics & Astronomy
Asteroseismic determination of obliquities of the exoplanet systems Kepler-50 and Kepler-65
Results on the obliquity of exoplanet host stars -- the angle between the
stellar spin axis and the planetary orbital axis -- provide important
diagnostic information for theories describing planetary formation. Here we
present the first application of asteroseismology to the problem of stellar
obliquity determination in systems with transiting planets and Sun-like host
stars. We consider two systems observed by the NASA Kepler Mission which have
multiple transiting small (super-Earth sized) planets: the previously reported
Kepler-50 and a new system, Kepler-65, whose planets we validate in this paper.
Both stars show rich spectra of solar-like oscillations. From the asteroseismic
analysis we find that each host has its rotation axis nearly perpendicular to
the line of sight with the sines of the angles constrained at the 1-sigma level
to lie above 0.97 and 0.91, respectively. We use statistical arguments to show
that coplanar orbits are favoured in both systems, and that the orientations of
the planetary orbits and the stellar rotation axis are correlated.Comment: Accepted for publication in ApJ; 46 pages, 11 figure
New constraints on dust grain size and distribution in CQ Tau
Grain growth in circumstellar disks is expected to be the first step towards
the formation of planetary systems. There is now evidence for grain growth in
several disks around young stars. Radially resolved images of grain growth in
circumstellar disks are believed to be a powerful tool to constrain the dust
evolution models and the initial stage for the formation of planets. In this
paper we attempt to provide these constraints for the disk surrounding the
young star CQ Tau. This system was already suggested from previous studies to
host a population of grains grown to large sizes. We present new high angular
resolution (0.3-0.9 arcsec) observations at wavelengths from 850um to 3.6cm
obtained at the SMA, IRAM-PdBI and NRAO-VLA interferometers. We perform a
combined analysis of the spectral energy distribution and of the
high-resolution images at different wavelengths using a model to describe the
dust thermal emission from the circumstellar disk. We include a prescription
for the gas emission from the inner regions of the system. We detect the
presence of evolved dust by constraining the disk averaged dust opacity
coefficient beta (computed between 1.3 and 7mm) to be 0.6+/-0.1. This confirms
the earlier suggestions that the disk contains dust grains grown to significant
sizes and puts this on firmer grounds by tightly constraining the gas
contamination to the observed fluxes at mm-cm wavelengths. We report some
evidence of radial variations in dust properties, but current resolution and
sensitivity are still too low for definitive results.Comment: 9 pages, A&A in pres
The architecture of the hierarchical triple star KOI 928 from eclipse timing variations seen in Kepler photometry
We present a hierarchical triple star system (KIC 9140402) where a low mass
eclipsing binary orbits a more massive third star. The orbital period of the
binary (4.98829 Days) is determined by the eclipse times seen in photometry
from NASA's Kepler spacecraft. The periodically changing tidal field, due to
the eccentric orbit of the binary about the tertiary, causes a change in the
orbital period of the binary. The resulting eclipse timing variations provide
insight into the dynamics and architecture of this system and allow the
inference of the total mass of the binary ()
and the orbital parameters of the binary about the central star.Comment: Submitted to MNRAS Letters. Additional tables with eclipse times are
included here. The Kepler data that was used for the analysis of this system
(Q1 through Q6) will be available on MAST after June 27, 201
Transit Timing Observations from Kepler: III. Confirmation of 4 Multiple Planet Systems by a Fourier-Domain Study of Anti-correlated Transit Timing Variations
We present a method to confirm the planetary nature of objects in systems
with multiple transiting exoplanet candidates. This method involves a
Fourier-Domain analysis of the deviations in the transit times from a constant
period that result from dynamical interactions within the system. The
combination of observed anti-correlations in the transit times and mass
constraints from dynamical stability allow us to claim the discovery of four
planetary systems Kepler-25, Kepler-26, Kepler-27, and Kepler-28, containing
eight planets and one additional planet candidate.Comment: Accepted to MNRA
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