81 research outputs found
False positive probabilties for all Kepler Objects of Interest: 1284 newly validated planets and 428 likely false positives
We present astrophysical false positive probability calculations for every
Kepler Object of Interest (KOI)---the first large-scale demonstration of a
fully automated transiting planet validation procedure. Out of 7056 KOIs, we
determine that 1935 have probabilities <1% to be astrophysical false positives,
and thus may be considered validated planets. 1284 of these have not yet been
validated or confirmed by other methods. In addition, we identify 428 KOIs
likely to be false positives that have not yet been identified as such, though
some of these may be a result of unidentified transit timing variations. A side
product of these calculations is full stellar property posterior samplings for
every host star, modeled as single, binary, and triple systems. These
calculations use 'vespa', a publicly available Python package able to be easily
applied to any transiting exoplanet candidate.Comment: 20 pages, 8 figures. Published in ApJ. Instructions to reproduce
results can be found at https://github.com/timothydmorton/koi-fp
Direct observation of microtubule dynamics at kinetochores in Xenopus extract spindles: implications for spindle mechanics
Microtubule plus ends dynamically attach to kinetochores on mitotic chromosomes. We directly imaged this dynamic interface using high resolution fluorescent speckle microscopy and direct labeling of kinetochores in Xenopus extract spindles. During metaphase, kinetochores were stationary and under tension while plus end polymerization and poleward microtubule flux (flux) occurred at velocities varying from 1.5–2.5 μm/min. Because kinetochore microtubules polymerize at metaphase kinetochores, the primary source of kinetochore tension must be the spindle forces that produce flux and not a kinetochore-based mechanism. We infer that the kinetochore resists translocation of kinetochore microtubules through their attachment sites, and that the polymerization state of the kinetochore acts a “slip-clutch” mechanism that prevents detachment at high tension. At anaphase onset, kinetochores switched to depolymerization of microtubule plus ends, resulting in chromosome-to-pole rates transiently greater than flux. Kinetochores switched from persistent depolymerization to persistent polymerization and back again during anaphase, bistability exhibited by kinetochores in vertebrate tissue cells. These results provide the most complete description of spindle microtubule poleward flux to date, with important implications for the microtubule–kinetochore interface and for how flux regulates kinetochore function
Central exclusive production of longlived gluinos at the LHC
We examine the possibility of producing gluino pairs at the LHC via the
exclusive reaction pp -> p+gluino+gluino+p in the case where the gluinos are
long lived. Such long lived gluinos are possible if the scalar super-partners
have large enough masses. We show that it may be possible to observe the
gluinos via their conversion to R-hadron jets and measure their mass to better
than 1% accuracy for masses below 350 GeV with 300/fb of data.Comment: 13 pages, 9 figures. Minor corrections to version
Terrestrial Planet Occurrence Rates for the Kepler GK Dwarf Sample
We measure planet occurrence rates using the planet candidates discovered by
the Q1-Q16 Kepler pipeline search. This study examines planet occurrence rates
for the Kepler GK dwarf target sample for planet radii, 0.75<Rp<2.5 Rearth, and
orbital periods, 50<Porb<300 days, with an emphasis on a thorough exploration
and identification of the most important sources of systematic uncertainties.
Integrating over this parameter space, we measure an occurrence rate of F=0.77
planets per star, with an allowed range of 0.3<F<1.9. The allowed range takes
into account both statistical and systematic uncertainties, and values of F
beyond the allowed range are significantly in disagreement with our analysis.
We generally find higher planet occurrence rates and a steeper increase in
planet occurrence rates towards small planets than previous studies of the
Kepler GK dwarf sample. Through extrapolation, we find that the one year
orbital period terrestrial planet occurrence rate, zeta_1=0.1, with an allowed
range of 0.01<zeta_1<2, where zeta_1 is defined as the number of planets per
star within 20% of the Rp and Porb of Earth. For G dwarf hosts, the zeta_1
parameter space is a subset of the larger eta_earth parameter space, thus
zeta_1 places a lower limit on eta_earth for G dwarf hosts. From our analysis,
we identify the leading sources of systematics impacting Kepler occurrence rate
determinations as: reliability of the planet candidate sample, planet radii,
pipeline completeness, and stellar parameters.Comment: 19 Pages, 17 Figures, Submitted ApJ. Python source to support Kepler
pipeline completeness estimates available at
http://github.com/christopherburke/KeplerPORTs
Planetary Candidates Observed by Kepler IV: Planet Sample From Q1-Q8 (22 Months)
We provide updates to the Kepler planet candidate sample based upon nearly
two years of high-precision photometry (i.e., Q1-Q8). From an initial list of
nearly 13,400 Threshold Crossing Events (TCEs), 480 new host stars are
identified from their flux time series as consistent with hosting transiting
planets. Potential transit signals are subjected to further analysis using the
pixel-level data, which allows background eclipsing binaries to be identified
through small image position shifts during transit. We also re-evaluate Kepler
Objects of Interest (KOI) 1-1609, which were identified early in the mission,
using substantially more data to test for background false positives and to
find additional multiple systems. Combining the new and previous KOI samples,
we provide updated parameters for 2,738 Kepler planet candidates distributed
across 2,017 host stars. From the combined Kepler planet candidates, 472 are
new from the Q1-Q8 data examined in this study. The new Kepler planet
candidates represent ~40% of the sample with Rp~1 Rearth and represent ~40% of
the low equilibrium temperature (Teq<300 K) sample. We review the known biases
in the current sample of Kepler planet candidates relevant to evaluating planet
population statistics with the current Kepler planet candidate sample.Comment: 12 pages, 8 figures, Accepted ApJ Supplemen
Planetary Candidates Observed by Kepler. VIII. A Fully Automated Catalog With Measured Completeness and Reliability Based on Data Release 25
We present the Kepler Object of Interest (KOI) catalog of transiting
exoplanets based on searching four years of Kepler time series photometry (Data
Release 25, Q1-Q17). The catalog contains 8054 KOIs of which 4034 are planet
candidates with periods between 0.25 and 632 days. Of these candidates, 219 are
new and include two in multi-planet systems (KOI-82.06 and KOI-2926.05), and
ten high-reliability, terrestrial-size, habitable zone candidates. This catalog
was created using a tool called the Robovetter which automatically vets the
DR25 Threshold Crossing Events (TCEs, Twicken et al. 2016). The Robovetter also
vetted simulated data sets and measured how well it was able to separate TCEs
caused by noise from those caused by low signal-to-noise transits. We discusses
the Robovetter and the metrics it uses to sort TCEs. For orbital periods less
than 100 days the Robovetter completeness (the fraction of simulated transits
that are determined to be planet candidates) across all observed stars is
greater than 85%. For the same period range, the catalog reliability (the
fraction of candidates that are not due to instrumental or stellar noise) is
greater than 98%. However, for low signal-to-noise candidates between 200 and
500 days around FGK dwarf stars, the Robovetter is 76.7% complete and the
catalog is 50.5% reliable. The KOI catalog, the transit fits and all of the
simulated data used to characterize this catalog are available at the NASA
Exoplanet Archive.Comment: 61 pages, 23 Figures, 9 Tables, Accepted to The Astrophysical Journal
Supplement Serie
The New Horizons Spacecraft
The New Horizons spacecraft was launched on 19 January 2006. The spacecraft
was designed to provide a platform for seven instruments that will collect and
return data from Pluto in 2015. The design drew on heritage from previous
missions developed at The Johns Hopkins University Applied Physics Laboratory
(APL) and other missions such as Ulysses. The trajectory design imposed
constraints on mass and structural strength to meet the high launch
acceleration needed to reach the Pluto system prior to the year 2020. The
spacecraft subsystems were designed to meet tight mass and power allocations,
yet provide the necessary control and data handling finesse to support data
collection and return when the one-way light time during the Pluto flyby is 4.5
hours. Missions to the outer solar system require a radioisotope thermoelectric
generator (RTG) to supply electrical power, and a single RTG is used by New
Horizons. To accommodate this constraint, the spacecraft electronics were
designed to operate on less than 200 W. The spacecraft system architecture
provides sufficient redundancy to provide a probability of mission success of
greater than 0.85, even with a mission duration of over 10 years. The
spacecraft is now on its way to Pluto, with an arrival date of 14 July 2015.
Initial inflight tests have verified that the spacecraft will meet the design
requirements.Comment: 33 pages, 13 figures, 4 tables; To appear in a special volume of
Space Science Reviews on the New Horizons missio
Masses, radii, and orbits of small Kepler planets : The transition from gaseous to rocky planets
We report on the masses, sizes, and orbits of the planets orbiting 22 Kepler stars. There are 49 planet candidates around these stars, including 42 detected through transits and 7 revealed by precise Doppler measurements of the host stars. Based on an analysis of the Kepler brightness measurements, along with high-resolution imaging and spectroscopy, Doppler spectroscopy, and (for 11 stars) asteroseismology, we establish low false-positive probabilities (FPPs) for all of the transiting planets (41 of 42 have an FPP under 1%), and we constrain their sizes and masses. Most of the transiting planets are smaller than three times the size of Earth. For 16 planets, the Doppler signal was securely detected, providing a direct measurement of the planet's mass. For the other 26 planets we provide either marginal mass measurements or upper limits to their masses and densities; in many cases we can rule out a rocky composition. We identify six planets with densities above 5 g cm-3, suggesting a mostly rocky interior for them. Indeed, the only planets that are compatible with a purely rocky composition are smaller than 2 R ⊕. Larger planets evidently contain a larger fraction of low-density material (H, He, and H2O).Peer reviewedFinal Accepted Versio
Combined rotation scarf and Akin osteotomies for hallux valgus: a patient focussed 9 year follow up of 50 patients
<p>Abstract</p> <p>Background</p> <p>The Cochrane review of hallux valgus surgery has disputed the scientific validity of hallux valgus research. Scoring systems and surrogate measures such as x-ray angles are commonly reported at just one year post operatively but these are of dubious relevance to the patient. In this study we extended the follow up to a minimum of 8 years and sought to address patient specific concerns with hallux valgus surgery. The long term follow up also allowed a comprehensive review of the complications associated with the combined rotation scarf and Akin osteotomies.</p> <p>Methods</p> <p>Between 1996 and 1999, 101 patients underwent rotation scarf and Akin osteotomies for the treatment of hallux valgus. All patients were contacted and asked to participate in this study. 50 female participants were available allowing review of 73 procedures. The average follow up was over 9 years and the average age at the time of surgery was 57. The participants were physically examined and interviewed.</p> <p>Results</p> <p>Post-operatively, in 86% of the participants there were no footwear restrictions. Stiffness of the first metatarsophalangeal joint was reported in 8% (6 feet); 10% were unhappy with the cosmetic appearance of their feet, 3 feet had hallux varus, and 2 feet had recurrent hallux valgus. There were no foot-related activity restrictions in 92% of the group. Metatarsalgia occurred in 4% (3 feet). 96% were better than before surgery and 88% were completely satisfied with their post-operative result. Hallux varus was the greatest single cause of dissatisfaction. The most common adverse event in the study was internal fixation irritation. Hallux valgus surgery is not without risk and these findings could be useful in the informed consent process.</p> <p>Conclusions</p> <p>When combined the rotation scarf and Akin osteotomies are an effective treatment for hallux valgus that achieves good long-term correction with a low incidence of recurrence, footwear restriction or metatarsalgia. The nature of the osteotomies allows early return to normal shoes and activity without the need for postoperative immobilisation in a plaster cast.</p
A Search for Additional Planets in the NASA EPOXI Observations of the Exoplanet System GJ 436
We present time series photometry of the M dwarf transiting exoplanet system
GJ 436 obtained with the the EPOCh (Extrasolar Planet Observation and
Characterization) component of the NASA EPOXI mission. We conduct a search of
the high-precision time series for additional planets around GJ 436, which
could be revealed either directly through their photometric transits, or
indirectly through the variations these second planets induce on the transits
of the previously known planet. In the case of GJ 436, the presence of a second
planet is perhaps indicated by the residual orbital eccentricity of the known
hot Neptune companion. We find no candidate transits with significance higher
than our detection limit. From Monte Carlo tests of the time series, we rule
out transiting planets larger than 1.5 R_Earth interior to GJ 436b with 95%
confidence, and larger than 1.25 R_Earth with 80% confidence. Assuming
coplanarity of additional planets with the orbit of GJ 436b, we cannot expect
that putative planets with orbital periods longer than about 3.4 days will
transit. However, if such a planet were to transit, we rule out planets larger
than 2.0 R_Earth with orbital periods less than 8.5 days with 95% confidence.
We also place dynamical constraints on additional bodies in the GJ 436 system.
Our analysis should serve as a useful guide for similar analyses for which
radial velocity measurements are not available, such as those discovered by the
Kepler mission. These dynamical constraints on additional planets with periods
from 0.5 to 9 days rule out coplanar secular perturbers as small as 10 M_Earth
and non-coplanar secular perturbers as small as 1 M_Earth in orbits close in to
GJ 436b. We present refined estimates of the system parameters for GJ 436. We
also report a sinusoidal modulation in the GJ 436 light curve that we attribute
to star spots. [Abridged]Comment: 29 pages, 8 figures, 3 tables, accepted for publication in Ap
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