123 research outputs found
Planet Hunters: New Kepler planet candidates from analysis of quarter 2
We present new planet candidates identified in NASA Kepler quarter two public
release data by volunteers engaged in the Planet Hunters citizen science
project. The two candidates presented here survive checks for false-positives,
including examination of the pixel offset to constrain the possibility of a
background eclipsing binary. The orbital periods of the planet candidates are
97.46 days (KIC 4552729) and 284.03 (KIC 10005758) days and the modeled planet
radii are 5.3 and 3.8 R_Earth. The latter star has an additional known planet
candidate with a radius of 5.05 R_Earth and a period of 134.49 which was
detected by the Kepler pipeline. The discovery of these candidates illustrates
the value of massively distributed volunteer review of the Kepler database to
recover candidates which were otherwise uncatalogued.Comment: Accepted to A
Interactions Between Moderate- and Long-Period Giant Planets: Scattering Experiments for Systems in Isolation and with Stellar Flybys
The chance that a planetary system will interact with another member of its
host star's nascent cluster would be greatly increased if gas giant planets
form in situ on wide orbits. In this paper, we explore the outcomes of
planet-planet scattering for a distribution of multiplanet systems that all
have one of the planets on an initial orbit of 100 AU. The scattering
experiments are run with and without stellar flybys. We convolve the outcomes
with distributions for protoplanetary disk and stellar cluster sizes to
generalize the results where possible. We find that the frequencies of large
mutual inclinations and high eccentricities are sensitive to the number of
planets in a system, but not strongly to stellar flybys. However, flybys do
play a role in changing the low and moderate portions of the mutual inclination
distributions, and erase dynamically cold initial conditions on average.
Wide-orbit planets can be mixed throughout the planetary system, and in some
cases, can potentially become hot Jupiters, which we demonstrate using
scattering experiments that include a tidal damping model. If planets form on
wide orbits in situ, then there will be discernible differences in the proper
motion distributions of a sample of wide-orbit planets compared with a pure
scattering formation mechanism. Stellar flybys can enhance the frequency of
ejections in planetary systems, but auto-ionization is likely to remain the
dominant source of free-floating planets.Comment: Accepted for publication by Ap
The growth and hydrodynamic collapse of a protoplanet envelope
We have conducted three-dimensional self-gravitating radiation hydrodynamical
models of gas accretion onto high mass cores (15-33 Earth masses) over hundreds
of orbits. Of these models, one case accretes more than a third of a Jupiter
mass of gas, before eventually undergoing a hydrodynamic collapse. This
collapse causes the density near the core to increase by more than an order of
magnitude, and the outer envelope to evolve into a circumplanetary disc. A
small reduction in the mass within the Hill radius (R_H) accompanies this
collapse as a shock propagates outwards. This collapse leads to a new
hydrostatic equilibrium for the protoplanetary envelope, at which point 97 per
cent of the mass contained within the Hill radius is within the inner 0.03 R_H
which had previously contained less than 40 per cent. Following this collapse
the protoplanet resumes accretion at its prior rate. The net flow of mass
towards this dense protoplanet is predominantly from high latitudes, whilst at
the outer edge of the circumplanetary disc there is net outflow of gas along
the midplane. We also find a turnover of gas deep within the bound envelope
that may be caused by the establishment of convection cells.Comment: 16 pages, 16 figures. Accepted for publication in MNRA
PS56 Acute Kidney Injury in Critically Ill Vascular Surgery Patients Is Associated With Increased Mortality Regardless of Severity and Type of Index Procedure
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
Architecture of Kepler's Multi-transiting Systems: II. New investigations with twice as many candidates
We report on the orbital architectures of Kepler systems having multiple
planet candidates identified in the analysis of data from the first six
quarters of Kepler data and reported by Batalha et al. (2013). These data show
899 transiting planet candidates in 365 multiple-planet systems and provide a
powerful means to study the statistical properties of planetary systems. Using
a generic mass-radius relationship, we find that only two pairs of planets in
these candidate systems (out of 761 pairs total) appear to be on Hill-unstable
orbits, indicating ~96% of the candidate planetary systems are correctly
interpreted as true systems. We find that planet pairs show little statistical
preference to be near mean-motion resonances. We identify an asymmetry in the
distribution of period ratios near first-order resonances (e.g., 2:1, 3:2),
with an excess of planet pairs lying wide of resonance and relatively few lying
narrow of resonance. Finally, based upon the transit duration ratios of
adjacent planets in each system, we find that the interior planet tends to have
a smaller transit impact parameter than the exterior planet does. This finding
suggests that the mode of the mutual inclinations of planetary orbital planes
is in the range 1.0-2.2 degrees, for the packed systems of small planets probed
by these observations.Comment: Accepted to Ap
A High Eccentricity Component in the Double Planet System Around HD 163607 and a Planet Around HD 164509
We report the detection of three new exoplanets from Keck Observatory. HD
163607 is a metal-rich G5IV star with two planets. The inner planet has an
observed orbital period of 75.29 0.02 days, a semi-amplitude of 51.1
1.4 \ms, an eccentricity of 0.73 0.02 and a derived minimum mass of
\msini = 0.77 0.02 \mjup. This is the largest eccentricity of any known
planet in a multi-planet system. The argument of periastron passage is 78.7
2.0; consequently, the planet's closest approach to its parent
star is very near the line of sight, leading to a relatively high transit
probability of 8%. The outer planet has an orbital period of 3.60 0.02
years, an orbital eccentricity of 0.12 0.06 and a semi-amplitude of 40.4
1.3 \ms. The minimum mass is \msini = 2.29 0.16 \mjup. HD 164509 is
a metal-rich G5V star with a planet in an orbital period of 282.4 3.8
days and an eccentricity of 0.26 0.14. The semi-amplitude of 14.2
2.7 \ms\ implies a minimum mass of 0.48 0.09 \mjup. The radial velocities
of HD 164509 also exhibit a residual linear trend of -5.1 0.7 \ms\ per
year, indicating the presence of an additional longer period companion in the
system. Photometric observations demonstrate that HD 163607 and HD 164509 are
constant in brightness to sub-millimag levels on their radial velocity periods.
This provides strong support for planetary reflex motion as the cause of the
radial velocity variations.Comment: 10 pages, 8 figures, accepted to Ap
- …