28 research outputs found
Detection of Potential Transit Signals in Sixteen Quarters of Kepler Mission Data
We present the results of a search for potential transit signals in four
years of photometry data acquired by the Kepler Mission. The targets of the
search include 111,800 stars which were observed for the entire interval and
85,522 stars which were observed for a subset of the interval. We found that
9,743 targets contained at least one signal consistent with the signature of a
transiting or eclipsing object, where the criteria for detection are
periodicity of the detected transits, adequate signal-to-noise ratio, and
acceptance by a number of tests which reject false positive detections. When
targets that had produced a signal were searched repeatedly, an additional
6,542 signals were detected on 3,223 target stars, for a total of 16,285
potential detections. Comparison of the set of detected signals with a set of
known and vetted transit events in the Kepler field of view shows that the
recovery rate for these signals is 96.9%. The ensemble properties of the
detected signals are reviewed.Comment: Accepted by ApJ Supplemen
Aberrations of TACC1 and TACC3 are associated with ovarian cancer
BACKGROUND: Dysregulation of the human Transforming Acidic Coiled Coil (TACC) genes is thought to be important in the development and progression of multiple myeloma, breast and gastric cancer. Recent, large-scale genomic analysis and Serial Analysis of Gene Expression data suggest that TACC1 and TACC3 may also be involved in the etiology of ovarian tumors from both familial and sporadic cases. Therefore, the aim of this study was to determine the occurrence of alterations of these TACCs in ovarian cancer. METHODS: Detection and scoring of TACC1 and TACC3 expression was performed by immunohistochemical analysis of the T-BO-1 tissue/tumor microarray slide from the Cooperative Human Tissue Network, Tissue Array Research Program (TARP) of the National Cancer Institute, National Institutes of Health, Bethesda, MD, USA. Tumors were categorized as either positive (greater than 10% of cells staining) or negative. Statistical analysis was performed using Fisher's exact test and p < 0.05 (single comparisons), and p < 0.02 (multiple comparisons) were considered to be significant. Transgenomics WAVE high performance liquid chromatography (dHPLC) was used to pre-screen the TACC3 gene in constitutional DNA from ovarian cancer patients and their unaffected relatives from 76 families from the Gilda Radner Familial Ovarian Cancer Registry. All variant patterns were then sequenced. RESULTS: This study demonstrated absence of at least one or both TACC proteins in 78.5% (51/65) of ovarian tumors tested, with TACC3 loss observed in 67.7% of tumors. The distribution pattern of expression of the two TACC proteins was different, with TACC3 loss being more common in serous papillary carcinoma compared with clear cell carcinomas, while TACC1 staining was less frequent in endometroid than in serous papillary tumor cores. In addition, we identified two constitutional mutations in the TACC3 gene in patients with ovarian cancer from the Gilda Radner Familial Ovarian Cancer Registry. These patients had previously tested negative for mutations in known ovarian cancer predisposing genes. CONCLUSION: When combined, our data suggest that aberrations of TACC genes, and TACC3 in particular, underlie a significant proportion of ovarian cancers. Thus, TACC3 could be a hitherto unknown endogenous factor that contributes to ovarian tumorigenesis
Planetary Candidates Observed by Kepler V: Planet Sample from Q1-Q12 (36 Months)
The Kepler mission discovered 2842 exoplanet candidates with 2 years of data.
We provide updates to the Kepler planet candidate sample based upon 3 years
(Q1-Q12) of data. Through a series of tests to exclude false-positives,
primarily caused by eclipsing binary stars and instrumental systematics, 855
additional planetary candidates have been discovered, bringing the total number
known to 3697. We provide revised transit parameters and accompanying posterior
distributions based on a Markov Chain Monte Carlo algorithm for the cumulative
catalogue of Kepler Objects of Interest. There are now 130 candidates in the
cumulative catalogue that receive less than twice the flux the Earth receives
and more than 1100 have a radius less than 1.5 Rearth. There are now a dozen
candidates meeting both criteria, roughly doubling the number of candidate
Earth analogs. A majority of planetary candidates have a high probability of
being bonafide planets, however, there are populations of likely
false-positives. We discuss and suggest additional cuts that can be easily
applied to the catalogue to produce a set of planetary candidates with good
fidelity. The full catalogue is publicly available at the NASA Exoplanet
Archive.Comment: Accepted for publication, ApJ
Kepler-16: A Transiting Circumbinary Planet
We report the detection of a planet whose orbit surrounds a pair of low-mass
stars. Data from the Kepler spacecraft reveal transits of the planet across
both stars, in addition to the mutual eclipses of the stars, giving precise
constraints on the absolute dimensions of all three bodies. The planet is
comparable to Saturn in mass and size, and is on a nearly circular 229-day
orbit around its two parent stars. The eclipsing stars are 20% and 69% as
massive as the sun, and have an eccentric 41-day orbit. The motions of all
three bodies are confined to within 0.5 degree of a single plane, suggesting
that the planet formed within a circumbinary disk.Comment: Science, in press; for supplemental material see
http://www.sciencemag.org/content/suppl/2011/09/14/333.6049.1602.DC1/1210923.Doyle.SOM.pd
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
Planetary Candidates Observed by Kepler VI: Planet Sample from Q1-Q16 (47 Months)
\We present the sixth catalog of Kepler candidate planets based on nearly 4
years of high precision photometry. This catalog builds on the legacy of
previous catalogs released by the Kepler project and includes 1493 new Kepler
Objects of Interest (KOIs) of which 554 are planet candidates, and 131 of these
candidates have best fit radii <1.5 R_earth. This brings the total number of
KOIs and planet candidates to 7305 and 4173 respectively. We suspect that many
of these new candidates at the low signal-to-noise limit may be false alarms
created by instrumental noise, and discuss our efforts to identify such
objects. We re-evaluate all previously published KOIs with orbital periods of
>50 days to provide a consistently vetted sample that can be used to improve
planet occurrence rate calculations. We discuss the performance of our planet
detection algorithms, and the consistency of our vetting products. The full
catalog is publicly available at the NASA Exoplanet Archive.Comment: 18 pages, to be published in the Astrophysical Journal Supplement
Serie
Planetary Candidates Observed by Kepler, III: Analysis of the First 16 Months of Data
New transiting planet candidates are identified in sixteen months (May 2009 -
September 2010) of data from the Kepler spacecraft. Nearly five thousand
periodic transit-like signals are vetted against astrophysical and instrumental
false positives yielding 1,091 viable new planet candidates, bringing the total
count up to over 2,300. Improved vetting metrics are employed, contributing to
higher catalog reliability. Most notable is the noise-weighted robust averaging
of multi-quarter photo-center offsets derived from difference image analysis
which identifies likely background eclipsing binaries. Twenty-two months of
photometry are used for the purpose of characterizing each of the new
candidates. Ephemerides (transit epoch, T_0, and orbital period, P) are
tabulated as well as the products of light curve modeling: reduced radius
(Rp/R*), reduced semi-major axis (d/R*), and impact parameter (b). The largest
fractional increases are seen for the smallest planet candidates (197% for
candidates smaller than 2Re compared to 52% for candidates larger than 2Re) and
those at longer orbital periods (123% for candidates outside of 50-day orbits
versus 85% for candidates inside of 50-day orbits). The gains are larger than
expected from increasing the observing window from thirteen months (Quarter 1--
Quarter 5) to sixteen months (Quarter 1 -- Quarter 6). This demonstrates the
benefit of continued development of pipeline analysis software. The fraction of
all host stars with multiple candidates has grown from 17% to 20%, and the
paucity of short-period giant planets in multiple systems is still evident. The
progression toward smaller planets at longer orbital periods with each new
catalog release suggests that Earth-size planets in the Habitable Zone are
forthcoming if, indeed, such planets are abundant.Comment: Submitted to ApJS. Machine-readable tables are available at
http://kepler.nasa.gov, http://archive.stsci.edu/kepler/results.html, and the
NASA Exoplanet Archiv
The kepler-19 system: a transiting 2.2 R ⊕ planet and a second planet detected via transit timing variations
We present the discovery of the Kepler-19 planetary system, which we first identified from a 9.3day periodic transit signal in the Kepler photometry. From high-resolution spectroscopy of the star, we find a stellar effective temperature T= 5541 60K, a metallicity [Fe/H] = -0.13 0.06, and a surface gravity log(g) = 4.59 0.10. We combine the estimate of T and [Fe/H] with an estimate of the stellar density derived from the photometric light curve to deduce a stellar mass of M = 0.936 0.040 M and a stellar radius of R = 0.850 0.018 R (these errors do not include uncertainties in the stellar models). We rule out the possibility that the transits result from an astrophysical false positive by first identifying the subset of stellar blends that reproduce the precise shape of the light curve. Using the additional constraints from the measured color of the system, the absence of a secondary source in the high-resolution spectrum, and the absence of a secondary source in the adaptive optics imaging, we conclude that the planetary scenario is more than three orders of magnitude more likely than a blend. The blend scenario is independently disfavored by the achromaticity of the transit: we measure a transit depth with Spitzer at 4.5 μm of 547+113 -110 ppm, consistent with the depth measured in the Kepler optical bandpass of 567 6 ppm (corrected for stellar limb darkening). We determine a physical radius of the planet Kepler-19b of Rp = 2.209 0.048 R ⊕; the uncertainty is dominated by uncertainty in the stellar parameters. From radial velocity observations of the star, we find an upper limit on the planet mass of 20.3 M ⊕, corresponding to a maximum density of 10.4 g cm -3. We report a significant sinusoidal deviation of the transit times from a predicted linear ephemeris, which we conclude is due to an additional perturbing body in the system. We cannot uniquely determine the orbital parameters of the perturber, as various dynamical mechanisms match the amplitude, period, and shape of the transit timing signal and satisfy the host star's radial velocity limits. However, the perturber in these mechanisms has a period ≲ 160days and mass ≲ 6 M Jup, confirming its planetary nature as Kepler-19c. We place limits on the presence of transits of Kepler-19c in the available Kepler data
The Occurrence of Rocky Habitable-zone Planets around Solar-like Stars from Kepler Data
We present the occurrence rates for rocky planets in the habitable zones (HZs) of main-sequence dwarf stars based on the Kepler DR25 planet candidate catalog and Gaia-based stellar properties. We provide the first analysis in terms of star-dependent instellation flux, which allows us to track HZ planets. We define η⊕ as the HZ occurrence of planets with radii between 0.5 and 1.5 R⊕ orbiting stars with effective temperatures between 4800 and 6300 K. We find that η⊕ for the conservative HZ is between 0.37^(+0.48)_(−0.21) (errors reflect 68% credible intervals) and 0.60^(+0.90)_(−0.36) planets per star, while the optimistic HZ occurrence is between 0.58^(+0.73)_(−0.33) and 0.88^(+1.28)_(−0.51) planets per star. These bounds reflect two extreme assumptions about the extrapolation of completeness beyond orbital periods where DR25 completeness data are available. The large uncertainties are due to the small number of detected small HZ planets. We find similar occurrence rates between using Poisson likelihood Bayesian analysis and using Approximate Bayesian Computation. Our results are corrected for catalog completeness and reliability. Both completeness and the planet occurrence rate are dependent on stellar effective temperature. We also present occurrence rates for various stellar populations and planet size ranges. We estimate with 95% confidence that, on average, the nearest HZ planet around G and K dwarfs is ~6 pc away and there are ~4 HZ rocky planets around G and K dwarfs within 10 pc of the Sun