62 research outputs found
Measuring Transit Signal Recovery in the Kepler Pipeline II: Detection Efficiency as Calculated in One Year of Data
The Kepler planet sample can only be used to reconstruct the underlying
planet occurrence rate if the detection efficiency of the Kepler pipeline is
known, here we present the results of a second experiment aimed at
characterising this detection efficiency. We inject simulated transiting planet
signals into the pixel data of ~10,000 targets, spanning one year of
observations, and process the pixels as normal. We compare the set of
detections made by the pipeline with the expectation from the set of simulated
planets, and construct a sensitivity curve of signal recovery as a function of
the signal-to-noise of the simulated transit signal train. The sensitivity
curve does not meet the hypothetical maximum detection efficiency, however it
is not as pessimistic as some of the published estimates of the detection
efficiency. For the FGK stars in our sample, the sensitivity curve is well fit
by a gamma function with the coefficients a = 4.35 and b = 1.05. We also find
that the pipeline algorithms recover the depths and periods of the injected
signals with very high fidelity, especially for periods longer than 10 days. We
perform a simplified occurrence rate calculation using the measured detection
efficiency compared to previous assumptions of the detection efficiency found
in the literature to demonstrate the systematic error introduced into the
resulting occurrence rates. The discrepancies in the calculated occurrence
rates may go some way towards reconciling some of the inconsistencies found in
the literature.Comment: 13 pages, 7 figures, 1 electronic table, accepted by Ap
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
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
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 4 yr 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, including two in multiplanet systems (KOI-82.06 and KOI-2926.05) and 10 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). 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 discuss 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
Detection of Potential Transit Signals in the First Three Quarters of Kepler Mission Data
We present the results of a search for potential transit signals in the first
three quarters of photometry data acquired by the Kepler Mission. The targets
of the search include 151,722 stars which were observed over the full interval
and an additional 19,132 stars which were observed for only 1 or 2 quarters.
From this set of targets we find a total of 5,392 detections which meet the
Kepler detection criteria: those criteria are periodicity of the signal, an
acceptable signal-to-noise ratio, and a composition test which rejects spurious
detections which contain non-physical combinations of events. The detected
signals are dominated by events with relatively low signal-to-noise ratio and
by events with relatively short periods. The distribution of estimated transit
depths appears to peak in the range between 40 and 100 parts per million, with
a few detections down to fewer than 10 parts per million. The detected signals
are compared to a set of known transit events in the Kepler field of view which
were derived by a different method using a longer data interval; the comparison
shows that the current search correctly identified 88.1% of the known events. A
tabulation of the detected transit signals, examples which illustrate the
analysis and detection process, a discussion of future plans and open,
potentially fruitful, areas of further research are included
Planetary Candidates Observed by Kepler. VII. The First Fully Uniform Catalog Based on The Entire 48 Month Dataset (Q1-Q17 DR24)
We present the seventh Kepler planet candidate catalog, which is the first to
be based on the entire, uniformly processed, 48 month Kepler dataset. This is
the first fully automated catalog, employing robotic vetting procedures to
uniformly evaluate every periodic signal detected by the Q1-Q17 Data Release 24
(DR24) Kepler pipeline. While we prioritize uniform vetting over the absolute
correctness of individual objects, we find that our robotic vetting is overall
comparable to, and in most cases is superior to, the human vetting procedures
employed by past catalogs. This catalog is the first to utilize artificial
transit injection to evaluate the performance of our vetting procedures and
quantify potential biases, which are essential for accurate computation of
planetary occurrence rates. With respect to the cumulative Kepler Object of
Interest (KOI) catalog, we designate 1,478 new KOIs, of which 402 are
dispositioned as planet candidates (PCs). Also, 237 KOIs dispositioned as false
positives (FPs) in previous Kepler catalogs have their disposition changed to
PC and 118 PCs have their disposition changed to FP. This brings the total
number of known KOIs to 8,826 and PCs to 4,696. We compare the Q1-Q17 DR24 KOI
catalog to previous KOI catalogs, as well as ancillary Kepler catalogs, finding
good agreement between them. We highlight new PCs that are both potentially
rocky and potentially in the habitable zone of their host stars, many of which
orbit solar-type stars. This work represents significant progress in accurately
determining the fraction of Earth-size planets in the habitable zone of
Sun-like stars. The full catalog is publicly available at the NASA Exoplanet
Archive.Comment: Accepted to the Astrophysical Journal Supplement Series. 30 pages, 9
figures, 7 tables. We make the DR24 robovetter decision code publicly
available at http://github.com/JeffLCoughlin/robovetter, with input and
output examples provided using the same data as contained in the full paper's
table
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