POSTER ABSTRACTSP0136. POSTER SESSION ITerrestrial, Habitable-Zone Exoplanet Frequency from <strong>Kepler</strong>. W. A. Traub, Jet Propulsion Laboratory, CaliforniaInstitute of Technology, 4800 Oak Grove Dr., M/S 301-355, Pasadena, CA 91109, wtraub@jpl.nasa.govIntroduction: Data from <strong>Kepler</strong>'s first 136 days ofoperation are analyzed to determine the distribution ofexoplanets with respect to radius, period, and host-starspectral type [1]. The analysis is extrapolated to estimatethe percentage of terrestrial, habitable-zone exoplanets.The <strong>Kepler</strong> census is assumed to be completefor bright stars (magnitude 0.5 Earth radius and periods
POSTER ABSTRACTSP0137. POSTER SESSION IDIFFERENCE IMAGING FOR AUTOMATED VALIDATION OF PLANET CANDIDATES IN THEKEPLER SCIENCE OPERATIONS CENTER PIPELINE. J. D. Twicken 1 (joseph.twicken@nasa.gov), S. T.Bryson 2 (stephen.t.bryson@nasa.gov), R. L. Gilliland 3 (gillil@stsci.edu), J. M. Jenkins 1 (jon.jenkins@nasa.gov),1 SETI Institute/<strong>NASA</strong> Ames Research Center, MS 244-30, Moffett Field, CA, 94035, USA, 2 <strong>NASA</strong> Ames ResearchCenter, 3 Space Telescope Science Institute.Long cadence targets for which a Threshold CrossingEvent (TCE) is generated in the Science OperationsCenter (SOC) Transiting Planet Search moduleare then processed in the Data Validation (DV) component[1], [2] of the SOC Pipeline. A transiting planetmodel is fitted to the light curve for each target, and asearch for additional planets is conducted by repeatingthe transit search on the residual light curve after themodel flux has been removed. The process is repeateduntil all planet candidates have been identified.A suite of automated tests is performed on all planetcandidates in DV for the purpose of aiding in thediscrimination between true planets and false positives.The validation tests that were implemented in the initialrelease of DV have been documented in [1]. Insubsequent releases, a difference imaging techniquehas been implemented to enhance the validationprocess for planet candidates. This technique aims tolocate the source of a transit signature in the photometricmask for the given target, and to estimate the offsetbetween the transit source and the target itself.Difference imaging is proving to be a powerful diagnosticfor identifying astrophysical false positivedetections due to background eclipsing binaries. It isalso proving to be valuable for identifying the truetransit source in crowded apertures. Difference images,centroids and offsets are computed on a quarterly basisfor each planet candidate due to the quarterly roll ofthe spacecraft. The offsets may be averaged, however,over multiple quarters to improve the sensitivity of thisdifference image diagnostic.For each planet candidate, mean in- and out-oftransitimages are constructed by averaging the flux inand near each transit on a per pixel basis, and then byaveraging over all transits for the given observingquarter. In- and out-of-transit cadences are identifiedthrough the transiting planet model that is fitted to thetarget light curve. A difference image is then generatedby subtracting the mean in-transit flux for each pixelfrom the mean out-of-transit flux.Transits are excluded from the respective images ifthe associated in- or out-of-transit cadences overlap (1)the transit of another planet candidate for the giventarget, (2) a known spacecraft anomaly (e.g. Earthpointfor data downlink, safe mode, attitude tweak, andmultiple-cadence loss of fine point), or (3) the start orend of the given quarter.The photocenters of the out-of-transit and differenceimages are computed by fitting the appropriatePixel Response Function (PRF) for the given channel.The out-of-transit centroid locates the target itself,subject to aperture crowding. The difference imagecentroid precisely locates the source of the transit signature(which may or may not be the given target). Theoffset between difference and out-of-transit image centroidsprovides both absolute and statistical measuresof the separation between target and transit source.The offset is also computed per planet candidateand observing quarter between the difference imagecentroid and the target location specified by its <strong>Kepler</strong>Input Catalog (KIC) celestial coordinates. The offsetfrom the KIC reference position is not subject to aperturecrowding but is subject to centroid bias.A difference image for KOI 140 in quarter 3 isshown in the figure below. This KOI has been identifiedas an astrophysical false positive. The mean outof-transitimage is shown in the upper right panel andthe mean in-transit image is shown in the lower left.The difference image in the upper left panel indicatesthat the “transit” source is offset by 1.5 pixels (5.9arcseconds) from the target which is marked by theout-of-transit image centroid and the KIC referenceposition.Funding for the <strong>Kepler</strong> Mission has been providedby the <strong>NASA</strong> Science Mission Directorate.References:[1] Wu, H. et al. (2010) Proc. SPIE 7740, 774019 1-12. [2] Tenenbaum, P. et al. (2010) Proc. SPIE 7740,77400J 1-12.2011 <strong>Kepler</strong> Science Conference - <strong>NASA</strong> Ames Research Center 147
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